Quantum Materials Symposium 2014 in conjunction with 14 th Korea Japan Taiwan Workshop on SCES

Transcription

1 Quantum Materials Symposium 2014 in conjunction with 14 th Korea Japan Taiwan Workshop on SCES February 22 26, 2014 Program & Abstracts 1

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3 Contents Scope 4 Invited Speakers 5 Time Table 6 Chairs & Titles 7 Poster Presentation 10 Abstracts 15 3

4 Scope The Quantum Materials Symposium 2014 (QMS14) is organized by the SCES (strongly correlated electron systems) community in Korea. It is sponsored by the Asia Pacific Center for Theoretical Physics (APCTP), Korea Institute for Advanced Study(KIAS), and the IBS (Institute for Basic Science), Center for Correlated Electron Systems (CCES). We bring world leaders on several fronts of strongly correlated electron physics to QMS14. In particular, QMS14 is held in conjunction with the 14th Korea-Japan- Taiwan workshop on SCES: which over the past 13 years has been an important regular meeting point for researchers working on SCES in the East Asian region. In keeping with the tradition of hosting the winter workshops at one of the ski resorts, the meeting takes place at Muju resort ( During the five days workshop we cover such topics as quantum magnetism, exotic metals, new materials, artificial generation of emergent phenomena, and superconductivity. Topics Quantum Magnetism Exotic Metals New Materials Artificial generation of emergent phenomena Superconductivity Organizers Yunkyu Bang (Chonnam University, chair) Jung Hoon Han (Sungkyunkwan University) Changyoung Kim (Yonsei University) Kee-Hoon Kim (Seoul National University) Jae-Hoon Park (Pohang University of Science and Technology) Je-Geun Park (Seoul National University, secretary) Kwon Park (Korea Institute of Advanced Studies) Tuson Park (Sungkyunkwan University) Jaejun Yu (Seoul National University) 4

5 Invited speakers Peter Armitage (Johns Hopkins Univ., USA) Aaron Bostwick (LBNL, USA) Chun-Fu Chang (MPI-CPFS, Germany) Kookrin Char (SNU, Korea) Sasha Chernyshev (UC Irvine, USA) Ya-Ping Chiu (NSYSU, Taiwan) Woo Seok Choi (SKKU, Korea) Ying Hao Chu (NCTU, Taiwan) Hiroshi Eisaki (AIST, Japan) Atshshi Fujimori (Univ. of Tokyo, Japan) Jason Gardner (NSRRC, Taiwan) Jon Goff (RHL, UK) Myung Joon Han (KAIST, Korea) Ke He (IOP, China) Clifford Hicks (MPI-CPFS, Germany) Di-Jing Huang (NSRRC, Taiwan) Hosub Jin (SNU, Korea) Takuro Katsufuji (Waseda Univ., Japan) Changyoung Kim (Yonsei Univ., Korea) KeeHoon Kim (SNU, Korea) Ki-Seok Kim (POSTECH, Korea) Tsuyoshi Kimura (Osaka Univ., Japan) Mahn Duc Le (SNU, Korea) Young Lee (MIT, USA) Ping-Hui Lin (Academia Sinica, Taiwan) Maxim Mostovoy (Groningen Univ., Netherlands) Minoru Nohara (Okayama Univ., Japan) Cheol Hwan Park (SNU, Korea) Jaehoon Park (POSTECH, Korea) Christian Ruegg (Univ. of Geneva & PSI, Switzerland) Shik Shin (Univ. of Tokyo, Japan) Yong-il Shin (SNU, Korea) Shigemasa Suga (Osaka Univ., Japan) Hide Takagi (Univ. of Tokyo, Japan) Alan Tennant (HBZ, Germany) Jaejun Yu (SNU, Korea) Timothy Ziman (ILL, France) 5

6 Time Table Fri (Feb. 21) Sat (Feb. 22) Sun (Feb. 23) Mon (Feb. 24) Tue (Feb. 25) Wed (Feb. 26) Opening Ceremony Chair: Je-Geun Park 08:50-09:00 YK Bang/ J Yu Session #1: Chair: Je-Geun Park Electronic Structure I 09:00-09:40 Shik Shin 09:40-:10:20 Jaehoon Park Session #4 Chair: Jaejun Yu Electronic Structure II 09:00-09:40 Atsushi Fujimori 09:40-:10:20 Changyoung Kim Session #7 Chair: J. Gardner Exotic Ground States I 09:00-10:00 Hide Takagi Session #8 Chair: J. Goff Exotic Ground States II 09:00-10:00 Maxim Mostovoy Session #11 Chair: A. Chernyshev Quantum Magnetism II 09:00-10:00 A. Tennant 10:20-10:40 10:20-10:40 10:00-10:20 10:00-10:20 10:00-10:20 Break Break Break Break Break 10:40-11:20 Chun-Fu Chang 11:20-12:00 Shigemasa Suga 10:40-11:20 Di-Jing Huang 11:20-12:00 Tsuyoshi Kimura 10:20-11:00 Yong-il Shin 11:00-11:40 C. Hicks 10:20-11:00 Ki-Seok Kim 11:00-11:40 Ke He 10:20-11:00 Y. Lee 11:00-11:40 Ch. Ruegg 15:00-18:00 Registration at Ensemble Hall Session #2 Chair: D. J. Huang Interface Physics 13:30-14:10 Jaejun Yu 14:10-14:50 Ya-Ping Chiu Session #5 Chair: H. Takagi New Materials II 13:30-14:10 Jason Gardner 14:10-14:50 Myung Joon Han Session #9 Chair: A. Tennant Quantum Magnetism I 13:30-14:30 A. Chernyshev Session #12 Chair: Yunkyu Bang Exotic Ground States III 13:30-14:30 T. Ziman 14:50-15:10 14:50-15:10 14:30-14:50 14:30-14:50 Break Break Break Break Free Discussion / 15:10-15:50 15:10-15:50 Excursion (4 14:50-15:30 14:50-15:30 Woo Seok Choi Minoru Nohara hours hiking M. D. Le Cheol Hwan Park 15:50-16:30 Ying Hao Chu 15:50-16:30 Kee Hoon Kim program at Deogyusan 15:30-16:10 J. Goff 15:30-16:10 P. Armitage 16:30-17:00 16:30-17:00 National Park in 16:10-16:30 16:10-16:30 preparation ) Break Break Break Closing Ceremony Session #3 Chair: T. Kimura New Materials I 17:00-17:40 Hiroshi Eisaki 17:40-18:20 Ping-Hui Lin Session #6 Chair: A. Fujimori New Materials III 17:00-17:40 Kookrin Char 17:40-18:20 Takuro Katsufuji Session #10 Chair: Tae Won Noh New Materials IV 16:30-17:30 A. Bostwick 17:30-18:10 Hosub Jin 18:00-20:00 Welcome Party Venue: Hotel Tirol B1 18:30-21:00 Banquet Venue: Symphony Hall 18:30-20:00 Poster Session (Snack and light beverage will be provided) Venue: Symphony Hall 6

7 Chairs & Titles Saturday, Fab. 22: Session #1: Electronic Structure I (Chair: Je-Geun Park) (O1) Shik Shin Ultra-high resolution laser-arpes Study on high Tc-Superconductors (O2) Jaehoon Park Exotic Ordering Behaviors in Metallic IrTe2 (O3) Chun-Fu Chang Soft x-ray absorption and diffraction on strongly correlated oxides (O4) Shigemasa Suga New era of photoelectron spectroscopy: complete 3D spin-polarized angle-resolved photoelectron spectroscopy by spin-polarized momentum-microscope Session #2: Interface Physics (Chair: D. J. Huang) (O5) Jaejun Yu Origin of Two-Dimensional Electron Gas at LaAlO3/SrTiO3 Interface and SrTiO3 Surface (O6) Ya-Ping Chiu Atomic-Scale Interfacial Electronic Structures across Hetero-Interfaces in Complex Oxides (O7) Woo Seok Choi Controlling characteristics of 2 dimensionally confined electrons in perovskite oxide heterostructures (O8) Ying Hao Chu The coupling of strongly correlated electron systems and multiferroic periodic domain patterns Session #3: New Materials I (Chair: T. Kimura) (O9) Hiroshi Eisaki Magnetism and superconductivity in the three-dimensional electronic structures of Fe pnictides (O10) Ping-Hui Lin Electronic Structure Evolution and the Metallic Behavior of FeTe Through the Magnetic transition Sunday, Feb. 23: Session #4: Electronic Structure II (Chair: Jaejun Yu) (O11) Atsushi Fujimori Photoinduced dynamics of spinel MnV2O4 as a spin-orbital coupled system 7

8 (O12) Changyoung Kim Orbital angular momentum driven spin Hall effect (O13) Di-Jing Huang High-resolution RIXS for studying low-energy excitations of transition-metal compounds (O14) Tsuyoshi Kimura Study of helix-chirality in spin and quadrupole orientations by resonant x-ray scattering Session #5: New Materials II (Chair: H. Takagi) (O15) Jason Gardner Spin Correlations in Tb2Ti2O7 and Tb2Sn2O7 (O16) Myung Joon Han Electronic structure, superconductivity, and ferromagnetism in nickelate superlattices (O17) Minoru Nohara Superconductivity at 45 K in CaFeAs2 and CaFe2As2 with La doping (O18) Kee Hoon Kim Manifestation of magnetic quantum fluctuations in the dielectric properties Session #6: New Materials III (Chair: A. Fujimori) (O19) Kookrin Char High mobility, stability, and bipolar dopability of transparent perovskite semiconductor BaSnO3 (O20) Takuro Katsufuji Photoinduced dynamics of spinel MnV2O4 as a spin-orbital coupled system Monday, Feb. 24: Session #7: Exotic Ground States I (Chair: J. Gardner) (O21) Hide Takagi Exotic electronic phases derived from semi-metals+ (O22) Yong-il Shin Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture (O23) C. Hicks Strong increase of Tc of Sr2RuO4 under both tensile and compressive strain Tuesday, Feb. 25: Session #8: Exotic Ground States II (Chair: J. Goff) (O24) Maxim Mostovoy Skyrmionics 8

9 (O25) Ki-Seok Kim Electric-field control of ferromagnetic moment in rare-earth orthoferrite (O26) Ke He Quantum anomalous Hall effect in magnetically doped topological insulator Session #9: Quantum Magnetism I (Chair: A. Tennant) (O27) A. Chernyshev Odd interactions in quantum magnets and liquids (O28) M. D. Le Observation of magnon decay and non-linear spin waves in LuMnO3 (O29) J. Goff Defects in spin ice Session #10: New Materials IV (Chair: Tae Won Noh) (O30) A. Bostwick Many Body Physics in Graphene with ARPES (O31) Hosub Jin Spin-orbital entangled jeff states in 4d and 5d transition metal systems Friday, Feb. 26: Session #11: Quantum Magnetism II (Chair: A. Chernyshev) (O32) A. Tennant TBA (O33) Y. Lee Neutron scattering studies of the kagomé lattice: quantum spin liquids and topological magnon bands (O34) Ch. Ruegg Quantum and thermal criticality in magnets Session #12: Exotic Ground States III (Chair: Yunkyu Bang) (O35) T. Ziman Correlation effects in skew scattering mechanisms of Anomalous and Spin Hall Effects (O36) Cheol Hwan Park Quasiparticle carrier dynamics in graphene from first principles (O37) P. Armitage Recent Thz results on quantum correlated matter 9

10 Poster Presentation [P1] S. Sakamoto XMCD study of the n-type high-tc ferromagnetic semiconductor (In,Fe)As:Be [P2] A. Iyama The Magnetoelectric Effect in FeSb2O4 Single Crystals [P3] H. Fujiwara Soft-X-ray Resonant Inelastic X-ray Scattering for Vanadium Oxides [P4] Yen-Lin Huang Electrostatic Switching of In-plane Anisotropic Superconductivity in YBa2Cu3O7-σ/ BiFeO3 Heterostructure [P5] Ying-Hui Hsieh The Electrical Modulation of Interface Conduction at the BiFeO3-CoFe2O4 Oxide Interface [P6] Yi-Hsuan Liu Investigation of Interfacial Electronic Properties of Superconductor YBa2Cu3O7-δ on Ferroelectric BiFeO3 Domain Walls by Scanning Tunneling Spectroscopy [P7] Hsiao-Yu Huang RIXS Studies of Magnetite Fe3O4 [P8] R. P. Wang High-Resolution, High-Efficiency Beamline and Spectrometer for Inelastic Soft X-ray Scattering [P9] Z. Y. Chen Strain effect on BiFeO3 thin films by X-ray absorption spectroscopy [P10] Jing-Ching Wang Electronic Properties across LaMnO3/SrMnO3 Herterointerface by Scanning Tunneling Microscopy and Spectroscopy [P11] Bo-Chao Huang Interfacial Electronic Structure Evolution across BiFeO3/La0.7Sr0.3MnO3 Complex Oxide Heterointerfaces [P12] Chieh-Ping Wang Polarization-induced changes in interfacial superconductivity at YBa2Cu3O7/BiFeO3 heterointerfaces by scanning tunneling spectroscopy [P13] Yung-Hsiang Chan Proximity-Induced Atomic-Scale Changes of Interfacial Electronic Structures across YBa2Cu3O7 δ/la2/3ca1/3mno3 by Scanning Tunneling Microscopy 10

11 [P14] K. Balamurugan Spin-flop transitions of Neel-type antiferromagnet Li2MnO3 and Li2Mn1 xtixo3 single crystals with honeycomb-lattice [P15] Hyung Joon Kim Thermal conductivity of a BaSnO3-δ single crystal [P16] Dong Hyun Jang Single crystal growth and characterization of transparent oxide semiconductor LaInO3 [P17] Miso Yun Single-Ion Anisotropy and Triangular-Lattice Antiferromagnet [P18] Jisoo Lee Verwey transition in nanoscale magnetite [P19] Kyongjun Yoo Frustrated magnetism in S=1/2 3D frustrated spin systems ACuTe2O6 (Pb, Sr) [P20] Kyung Ik Sim Terahertz electrodynamics of superconducting NbTiN [P21] Kyujin Choi Optical Response of Graphene Oxide [P22] Taewoo Ha Optical Properties of Ba0.96La0.04SnO3 and Ba0.95Sb0.05SnO3 Thin Films with Perovskite Structure [P23] Hyun-Jung Kim Effects of Self-Interaction Correction and Spin-Orbit Coupling on the Insulating Phase of Na2IrO3 [P24] Byung Cheol Park Terahertz properties of doped Bi2Te3 single crystals [P25] Alexander C. Archer Emergence of frustrated antiferromagnet in the lowest Landau level [P26] Bumsung Lee Large Upper Critical Fields in a New Quasi-one-dimensional Superconductor Nb2PdxSe5 [P27] Suk-Young Park Electro-Optical Plasmonic Switch Based on Graphene [P28] Garam Han Localized characteristic evidence for charge transfer transition in NiS2-xSex 11

12 [P29] S. H. Cho The superconductivity of graphite intercalation compounds study in CaC6 using Angleresolved photoemission spectroscopy [P30] Shoresh Soltani Exchange local field correction to the dielectric function of graphene [P31] Cheng-Tai Kuo Optimization of the growth conditions of strontium iridates thin films [P32] Sooran Kim Electronic and magnetic properties of metal-insulator transition in ferromagnetic insulator K2Cr8O16 [P33] Minjae Kim Correlated Electronic Structures Phase Diagram of Hydrocarbon Superconductors using the Dynamical Mean-Field Theory [P34] Joosung Oh Magnon breakdown in a two dimensional triangular lattice Heisenberg antiferromagnet LuMnO3 [P35] Hyang Keun Yoo Emergence of latent orders in metallic LaNiO3 films by strain control of Fermi-surface topology [P36] Yong-Soo Jho Weyl metal: Toward interacting topological states of matter [P37] Min-Ho Kim Toward novel metallic states: Two-dimensional Fermi Liquids Revisited [P38] J. Shin Numerical analysis of spin-flip transitions in frustrated spin tetrahedral compound Cu4Te5O12Cl4 [P39] Shin Hee Yun Epitaxial Tungsten Oxide Thin Films [P40] Ji Soo Lim Change of electronic structure arising from oxygen vacancy migration in Ca doped BiFeO3 thin films [P41] K. E. Kim Enhanced electric formation of functional long range stripe nanostructures based on a morphotropic phase boundary 12

13 [P42] H. Y. Choi, J. Y. Moon Metamagnetic Transitions with the Formation of Magnetic Clusters in Single Crystalline Double Perovskite Eu2CoMnO6 [P43] Nara Lee Magnetic Control of Ferroelectric Polarization in a Self formed Single Magnetoelectric Domain of Multiferroic Ba3NbFe3Si2O14 [P44] N. Lee, S. H. Oh Multiferroicity in Single Crystalline Lu2CoMnO6 [P45] Y. J. Choi Giant Anistropic Magnetoresistance in Sr2IrO4 [P46] Chang Jong Kang Charge Ordering Phase in LuFe2O4 [P47] W. J. Lee, S. H. Lee Anomalous spin dynamics of the decorated Shastry Sutherland compound CdCu2(BO3)2 investigated by 11B NMR and μsr [P48] Kyung min. Kim Random chiral gauge field in magnetic doped topological insulators [P49] Heejung Kim The charge density wave instability in RE2O2Sb [P50] Bongjae Kim Electronic structure and magnetic properties of ultrathin SrRuO3(111) film [P51] Nam Wook Kim Half metallic ferromagnetism of Sn doped SrRuO3 perovskite oxide: A first principles prediction [P52] Jinyoung Lim Electronic Structure and Magnetic Properties of SrCoO2.5+x (x=0, 0.25, 0.5) [P53] Cheol Kim First Principles Total Energy Analysis of Various Ta2O5 Polymorphs [P54] J. H. Lee Tensile Strain Driven Morphotropic Phase Boundary of Rhombohedral and Orthorhombic BiFeO3 [P55] Rokyeon Kim Charge and magnetic states of rutile TiO2 doped with Cr ions 13

14 [P56] Jaehong Jeong The interplay of Dzyaloshinskii Moriya interaction and single ion anisotropy in multiferroic BiFeO3 [P57] Hasung Sim Long and short range structure of multiferroic Pb(Fe0.5Nb0.5)O3 [P58] J. K. Jung Direct observation of orbital ordering in TM doped iron pnictide 14

15 Abstracts 15

16 [O1] Ultra-high resolution laser-arpes Study on high Tc-Superconductors Shik Shin Institute for Solid State Physics (ISSP), University of Tokyo Angle resolved photoemission spectroscopy (ARPES) is very powerful to know the solid state properties, because we can know the solid state electrons directly. We have developed lowtemperature high-resolution laser-based ARPES system and recently achieved the highest energy resolution of ~ 100 μev and the lowest sample temperature of ~ 1.0 K. We confirmed the performance of the laser-arpes apparatus by the measurement of the superconducting gaps of the several low-tc elemental superconductors (Re: Tc=1.7 K, Al: Tc=1.2 K). Laser ARPES is found to be very useful for the superconductors, strongly-correlated materials, and heavy Fermion materials, organic materials. We would like to show our recent results of superconducting-gap measurements on Bi2212 by laser-arpes. Identifying temperature dependence of the pairing gap in cuprates is essential to formulate the mechanism of high temperature superconductivity. The pairing gap, observed near the nodal, was previously proposed to be rather conventional, closing at the superconducting transition temperature (Tc) with the BCS temperature dependence. By using a laser-arpes spectroscopy with an ultra-high energy resolution, we reveal that the d-wave gap with a point node, in fact, persists up to far above Tc (Tpair~1.5Tc) in the optimally doped Bi

17 [O2] Exotic Ordering Behaviors in Metallic IrTe2 K.-T. Ko 1,2,3, H.-H. Lee 1,2,3, D.-H. Kim 1,2,3, J.-J. Yang 2,4, T. A. Tyson 5, S-W. Cheong 2,4,5, R. Gammag 3, K.-S. Kim 3, H.-S. Kim 3,6, T.-H. Kim 3,6, H.-W. Yeom 3,6, J. S. Kim 3, T.-Y. Koo 7, H.-D. Kim 7, and J.-H. Park 1,2,3 1 Center for Cross-coupled Complex Materials Research, POSTECH, Pohang , Korea 2 Max Plank POSTECH Center for Complex Materials Research, POSTECH, Pohang , Korea 3 Department of Physics, POSTECH, Pohang , Korea 4 Lab. for Pohang Emergent Materials & Department of Physics, POSTECH, Pohang , Korea 5 Rutgers Center for Emergent Materials and Department of Physics & Astronomy, Rutgers University, Piscataway New Jersey 08854, USA 6 Center for Low Dimensional Electronic Systems, Institute for Basic Science (IBS), POSTECH, Pohang , Korea 7 Pohang Accelerator Laboratory, POSTECH, Pohang , Korea The strong spin-orbit coupling has become a key issue in the condensed matter physics in the last decade since discovery of its related emerging phenomena such as multiferroicity, topological insulator, noble Jeff = 1/2 Mott state. Recently, the 5d transition metal compound IrTe2 system has been reported to exhibit an exotic charge density wave (CDW) behavior. Furthermore, the system also exhibits superconductivity with suppression of CDW by Pt or Pd doping on the Ir sites. Differently from the 3d electrons, which show strong localized characters governed by the on-site Coulomb repulsion U, the 5d electrons have been widely considered as band-like itinerant electrons since their on-site U is much reduced and the band width W largely increases. On the other hand, the relativistic spin-orbit coupling energy, which is small to be treated as a perturbation term in the 3d transition metal, becomes so large that it can completely disturb the electronic structure in the 5d system. Here we discuss the exotic ordering behaviours in IrTe2 based on comprehensive studies of the macrsoscopic transport data, the microscopic synchrotron based spectroscopic and scattering results, and Atomic scale scanning tunnelling microscope results. 17

18 [O3] Soft x-ray absorption and diffraction on strongly correlated oxides Chun-Fu Chang Max Planck Institute for Chemical Physics of Solids Noethnitzer Strasse 40, Dresden, Germany Rich physical properties of correlated materials originate from the cooperative behaviors of charge, spin, orbital as well as their couplings to the lattice. Indeed, this electronic complexity has been regarded as a crucial role to understand many epochal phenomena such as superconductivity, colossal magnetoresistance, multiferroics, metal-insulator transition and so on. Over the last few decades, both experimental and theoretical developments have been progressive, however still there are many underlying mechanisms far from clear. A direct probing of charge, spin, and orbital states in these systems can be of great help to unravel the underlying physics of these novel phenomena. The well-developed soft x-ray absorption spectroscopy (XAS) is extremely sensitive to the local electronic structure, i.e., charge, spin, and orbital states of the ground state. Sharing the same optical transitions, resonant soft x-ray diffraction (RSXD) delivers the ordered (structureselective) information. In this talk we will present our studies on La1.5Sr0.5CoO4 and Fe3O4 by means of these two spectroscopic methods. 18

19 [O4] New era of photoelectron spectroscopy: complete 3D spin-polarized angle-resolved photoelectron spectroscopy by spin-polarized momentummicroscope S.Suga Institute of Scientific & Industrial Research, Osaka University 8-1 Mihogaoka, Ibaraki, Osaka Angle resolved and spin polarized photoelectron spectroscopy is a powerful means to study electronic structures of various solids ranging from magnetic materials to non-magnetic materials owing to the dipole selection rules with polarized light excitation. The low efficiency of spin-detectors, however, strongly limited its application to wide variety of materials up to now. Recent development of higher efficiency spin detectors such as Fe-O as well as two dimensional spin detectors as W and Ir-Au has overcome the strong limitation of spin-polarized angle resolved photoelectron spectroscopy (SP-ARPES) in very recent years. In addition, the development of a momentum microscope composed of a PEEM entrance lens and a tandem double hemispherical electron energy analyzers has facilitated two dimensional ARPES with simultaneous kx,ky measurement by a two dimensional detector in the form of EB(kx,ky). By inserting a two dimensional spin-detector after the tandem hemispherical analyzer, one can measure the spin polarization of photoelectrons in the form of P(EB(kx,ky)). The efficiency of the SP-ARPES is upgraded by more than 10,000 times than that of traditional SP-ARPES and now full set of information on electronic structures is easily available. History as well as the present status of multi-dimensional SP-ARPES is discussed in this presentation. 19

20 [O5] Origin of Two-Dimensional Electron Gas at LaAlO3/SrTiO3 Interface and SrTiO3 Surface Jaejun Yu Department of Physics and Astronomy, Seoul National University Recently the interface of two insulating LaAlO3 (LAO) and SrTiO3 (STO) oxides was discovered to be metallic and further reported to exhibit magnetism as well as superconductivity. While two dimensional electron gas at the n-type LAO/STO interface was suggested to arise from a so-called polar catastrophe concept, which is based on a simple idea of electrostatic breakdown of a polar insulating interface consisting of ionic charges, the origin of a twodimensional electron gas (2DEG) at the LAO/STO interface remains unclear despite the enormous activities on this system. In this talk we propose a phenomenological model for understanding electronic and redox screening at the surface and interface of oxide heterostructures based on first-principles calculation results. 20

21 [O6] Atomic-Scale Interfacial Electronic Structures across Hetero- Interfaces in Complex Oxides Ya-Ping Chiu Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan Interfaces have gotten a lot of attention recently and provide a powerful route to create and manipulate the charge, spin, orbital, and lattice degrees of freedom. Motivated by the importance of the critical nanoscale interfacial science that governs the applications of devices, the objective of our studies is emphasized the interfacial characteristics of hetero-epitaxial structures, and elucidated the fundamental mechanisms that pertain in these systems. In our studies, cross-sectional scanning tunneling microscopy is employed to observe directly the epitaxial interfacial structures and the local electronic properties with atomic-level insight. Our scanning tunneling microscopy and spectroscopy studies with atomic precision provide direct experimental insight into the origin and the natural evolution of the electronic properties across heterointerfaces in complex oxides, which provide a lot of insights to this community. Selected references: 1. Min-Chuan Shih, Bo-Chao Huang, Chih-Cheng Lin, Shao-Sian Li, Hsin-An Chen, Ya-Ping Chiu *, Chun-Wei Chen *, Atomic-Scale Interfacial Band Mapping across Vertically Phased- Separated Polymer/Fullerene Hybrid Solar Cells, Nano Letters, 13, 2387 (2013). 2. Bo-Chao Huang, Ya-Ping Chiu *, Po-Cheng Huang, Wen-Ching Wang, Vu Thanh Tra, Jan-Chi Yang, Qing He, Jiunn-Yuan Lin, Chia-Seng Chang, Ying-Hao Chu, Mapping Band Alignment across Complex Oxide Heterointerfaces, Phys. Rev. Lett., 109, (2012). 3. Ya-Ping Chiu*, Yu-Ting Chen, Bo-Chao Huang, Min-Chuan Shih, Jan-Chi Yang, Qing He, Chen-Wei Liang, Jan Seidel, Yi-Chun Chen, Ramamoorthy Ramesh, Ying-Hao Chu, Atomicscale evolution of local electronic structure across multiferroic domain walls, Adv. Mater., 23, 1530 (2011). 4. B. C. Huang, Y. T. Chen, Y. P. Chiu*, Y. C. Huang, J. C. Yang, Y. C. Chen, Y. H. Chu, Direct observation of ferroelectric polarization-modulated band bending at oxide interfaces, Appl. Phys. Lett. 100, (2012). 5. Y. P. Chiu*, B. C. Huang, M. C. Shih, J. Y. Shen, P. Chang, C. S. Chang, M. L. Huang, M. -H. Tsai, M. Hong*, and J. Kwo*, Atomic-scale Determination of Band Offsets at the Gd 2 O 3 /GaAs (100) Hetero-interface Using Scanning Tunneling Spectroscopy, Appl. Phys. Lett. 99, (2011). 21

22 [O7] Controlling characteristics of 2 dimensionally confined electrons in perovskite oxide heterostructures Woo Seok Choi Department of Physics, Sungkyunkwan University, Suwon, Gyeonggi-do , Korea Transition metal oxides exhibit vastly diverse physical properties based on strong correlation between the transition metal electrons and oxygen ions. Among the emergent phenomena, electron gas formed at the interface between two perovskite oxides has attracted tremendous recent attention due to its intriguing physics and possibility for novel device applications. LaTiO3/SrTiO3 (LTO/STO) heterostructure is one of the prominent examples which exhibit such intriguing 2D conduction, even though the constituents are normally insulating. More interestingly, the bulk counterpart, LaxSr1-xTiO3 (LSTO) exhibits a filling-controlled insulatormetal transition (IMT). In this study, we investigated the filling controlled IMT in 2 dimension by fabricating fractionally δ-doped LSTO/STO superlattices (SLs), in order to understand and control the charge carrier characteristics. Fractional layers of LSTO have been grown in between STO layers using advanced pulsed laser epitaxy. It is found that the transport properties are governed by a multichannel conduction with at least two distinctly different carriers: (1) High-densitylow-mobility carriers presenting at the LSTO layer and (2) low-density-high-mobility carriers residing in the STO layers, spatially away from the δ-doped layer. By optimizing x, we could tune the effective mass and carrier density to enhance the carrier mobility by about an order of magnitude, selectively for the high-density-low-mobility carriers. This suggests that the fractional δ-doping is an effective way to controlling the properties of charge carriers in oxide 2DEGs. 22

23 [O8] The coupling of strongly correlated electron systems and multiferroic periodic domain patterns Ying-Hao Chu 1,2 1 Department of Materials Science & Enginnering, National Chiao-Tung University, Hsinchu 30010, Taiwan 2 Institutes of Physics, Academia Sinica, Taipei 100, Taiwan Strongly correlated electron systems have drawn lots of attentions due to the interactions between order parameters spin, charge, lattice, and/or orbital. These interactions cause intriguing phenomena, such as high temperature superconductivity, multiferroics, colossal magneto-resistance, and then offer crucial opportunities for developing new electronic devices. In this talk, we propose a novel process to manipulate the entanglement of these systems by fabricating heteroepitaxial structures composing of strongly correlated electron systems with periodic BiFeO3 domain structure. The periodic domain structures of BiFeO3 are electrically controllable and provide a variety of strain modulation, electrostatic modification, and magnetic interaction to interact with order parameters in strongly correlated electron systems. Our results show strongly anisotropic transport behaviors captured by different temperatures of metal-insulator transition and superconducting transition, which are potentially electrically controllable. The coupling behaviors between periodic domain and strongly correlated systems are explored based on various techniques. The combinations of these materials would offer the insights of the interplays between order parameters as well as new solutions to next-generation electronic devices. 23

24 [O9] Utilizing high-pressure techniques for developing new superconductors / elevating superconducting transition temperatures Hiroshi Eisaki, Akira Iyo, Nao Takeshita, Hijiri Kito, Shigeyuki Ishida National Institute of Advanced Industrial Science and Technology (AIST) Throughout the history of high transition temperature (high-tc) superconductivity, highpressure (HP) technique has been playing significant roles. Sample synthesis under HP conditions (typically several GPa) turned out to be more advantageous compared to the conventional ambient pressure methods in many respects, such as the controlled modification of the phase diagram, enhanced reactivity, and prevention of the evaporation, etc. Using HP synthesis technique, various cuprates and iron-based high-tc superconductors have been discovered so far. It is also well recognized that the application of HP on the synthesized samples results in changing their structural parameters (bond length, bond angle, etc.) which determine their physical properties (density of states, phonon frequencies, magnetic coupling energy, etc.,) thus dramatically affects their superconducting properties. In this presentation, we will report on our recent trials in sample synthesis/physical properties measurements using HP techniques, which include the discovery of several superconductors and the successful observation of zero-resistivity above 150K in the mercury-based cuprate superconductors. 24

25 [O10] Electronic Structure Evolution and the Metallic Behavior of FeTe Through the Magnetic transition Ping-Hui Lin Institute of Physics, Academia Sinica, Taiwan We investigate with angle-resolved photoelectron spectroscopy (ARPES) the changes of the Fermi surface and the main bands from the paramagnetic state to the antiferromagnetic state. By combining ARPES measurements in different experimental geometric configurations, we have isolated the main bands of in the iron-based superconductors and studied their evolution through the magnetic or superconducting transitions. Our observations correlate well with the changes observed in transport measurements occurring below 72 K in FeTe. Previous ARPES results have presented several similarities in the electronic structure of ironbased systems, whereas the hole-like and electron-like states near the EF have Fe 3d character. Despite these similarities, the actual magnetic structures are different for the magnetic ironchalcogenide and iron-pnictide systems. In the pnictides, spins align in stripes with the wave vector along (π, π) direction. In FeTe, the magnetic ordering exhibits a double stripe magnetic order with the associating wave vector, QAFM =(π, 0), rotated by 45 with respect to the one of iron-pnictide. Consequently, the evolution of FeTe through the magnetic transition is completely different from that observed in Fe pnictides, as nesting is absent. The AFM state of FeTe is a rather good metal, in agreement with our magnetic band structure calculation. On the other hand, the anomalous FeTe electronic structure at the paramagnetic state deviates strongly from the band calculation, with a large pseudogap of 65 mev on the electron pocket that closes in the AFM state. In this talk I will discuss this behavior in connection with spin fluctuations existing above the magnetic transition and the correlations predicted in the spin-freezing regime of the incoherent metallic state. Reference: 1. P.-H. Lin, Y. Texier, A. Taleb-Ibrahimi, P. Lefevre, F. Bertran and V. Brouet, Phys. Rev. Lett, 111, (2013) 2. V. Brouet, M. Fuglsang Jensen, P.-H. Lin, A. Taleb-Ibrahimi, P. Le fevre, F. Bertran, C.-H. Lin, W. Ku, A. Forget, and D. Colson, Phys. Rev. B, 86, (2012) 3. M. Fuglsang Jensen, V. Brouet, E. Papalazarou, A. Nicolaou, A. Taleb-Ibrahimi, P. Le fevre, F. Bertran, A. Forget, and D. Colson, Phys. Rev. B, 84, (2011) 25

26 [O11] Magnetism and superconductivity in the three-dimensional electronic structures of Fe pnictides Atsushi Fujimori Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo Interplay between magnetism, structural distortion, and superconductivity is the essential characteristic of Fe-based superconductors. However, fundamental issues such as whether the magneto-structural phase transition is driven by Fermi-surface (FS) nesting or local magnetic interaction and how important the FS nesting is for superconductivity have remained unsettled. To resolve these issues, studies on systems with different c-axis parameters will give useful insight since the three-dimensionality of FSs and magnetic interaction between neighboring FeAs layers should sensitively depend on the distance between the layers. We have studied the FSs, band dispersions, and superconducting gaps of the BaFe2(As,P)2 [1,2] and SrFe2(As,P)2 systems using ARPES and DFT calculations. The TN of the parent compound as well as the Tc of the optimally doped compound are higher in the SrFe2(As,P)2 system than BaFe2(As,P)2 [3]. Hole FSs are found to be more strongly warped in SrFe2(As,P)2, suggesting that the magnetic ordering is driven by local magnetic interaction including interlayer one. Mass renormalization is found to be stronger in SrFe2(As,P)2, consistent with the stronger magnetism. The superconducting gap is more anisotropic for the electron and hole FSs in BaFe2(As,P)2 [1] and SrFe2(As,P)2, respectively, that is, gap anisotropy and FS warping seem correlated. This work has been done in collaboration with H. Suzuki, S. Ideta, T. Yoshida, K. Okazaki, T. Shimojima, Y. Ohta, S. Shin, M. Hashimoto, D. Lu,Z.-X. Shen,H. Anzai, A. Ino, M. Arita, H. Namatame, M. Taniguchi, H. Kumigashira, K. Ono, T. Kobayashi, S. Miyasaka, S. Tajima, S. Kasahara, T. Terashima, T. Shibauchi, Y. Matsuda, M. Nakajima, Y. Tomioka, T. Itoh, K. Kiho, C.-H. Lee, A. Iyo, H. Eisaki, and S. Uchida. Reference: [1] T. Yoshida et al., Phys. Rev. Lett. 106, (2011) [2] T. Yoshida et al., arxiv: [3] T. Kobayashi et al., Phys. Rev. B 87, (2013) 26

27 [O12] Orbital angular momentum driven spin Hall effect Changyoung Kim Department of Physics, Yonsei University, Seoul, Korea Orbital angular momentum (OAM), usually ignored in solids (OAM quenching), is found to play an important role in the electronic structure for a broad range of materials. In our previous work on the Rashba effect,[1,2] we obtained a new effective Hamiltonian that incorporates the role of OAM and explains many aspects of the Rashba effect. We apply the effective Hamiltonian to the problem of spin Hall effect (SHE). The key aspect of our interpretation is that the driving force comes from the OAM, caused by the coupling the applied electric field and asymmetric charge distribution described by the new effective Hamiltonian. SHE then comes as a side effect through the spin-orbit coupling. An important result of this view is that the Rashba and SHE are driven by the same microscopic mechanism. The proposed model can quantitatively predict the magnitude of SHE and account for the material dependent sign reversal of spin Hall current,. Reference: [1] S. R. Park, Phys. Rev. Lett.,108, (2012) [2] S. R. Park, Phys. Rev. Lett.,107, (2011) 27

28 [O13] High-resolution RIXS for studying low-energy excitations of transition-metal compounds Di-Jing Huang National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan Complex materials such as transition-metal oxides exhibit various intriguing phenomena, including high-temperature superconductivity, metal-insulator transition, and multiferroicity. Recent developments of material synthesis and spectroscopic techniques in the soft x-ray regime provide us great opportunities to unravel interesting phenomena of these novel materials. In this talk, we will present our recent development on resonant inelastic soft X-ray scattering (RIXS) spectroscopy to study low-energy excitations of transition-metal compounds. The design of the monochromator and spectrometer is based on the energy-compensation principle of grating dispersion which greatly enhances the efficiency of measurement of inelastic soft X-rays scattering. Test measurements of this new system will be discussed, including spinflip, d-d and charge-transfer excitations of NiO and Fe3O4 28

29 [O14] Study of helix-chirality in spin and quadrupole orientations by resonant x-ray scattering T. Kimura 1, Y. Tanaka 2, Y. Hirakaoka 1, T. Usui 1, H. Nakajima 1, M. Taguchi 2, A. Chainani 2, M. Oura 2, S. Shin 2,3, and Y. Wakabayashi 1 1 Graduate School of Engineering Science, Osaka University 2 RIKEN SPring-8 Center 3 ISSP, University of Tokyo Resonant x-ray scattering is known as powerful technique to study symmetry breakings by orderings of various multipole moments, such as spin and orbital. This technique is recently applied to verify symmetry breakings by the development of the chirality which is determined as an asymmetry of the object upon its mirroring in crystallography and magnetism, and which plays a crucial role in various materials functionality such as piezoelectricity and multiferroicity. With the help of the resonant x-ray scattering technique using circularlypolarized and highly-focused x-ray beam, we investigated the helix-chiral domains of magnetic dipole and electric quadrupole moments in magnetoelectric-related systems with right-handed and left-handed helical structures. 29

30 [O15] Spin Correlations in Tb2Ti2O7 and Tb2Sn2O7 J. S. Gardner 1, G. Ehlers 2, B. D. Gaulin 3 1 Neutron Group, NSRRC, Hsinchu, 30076, Taiwan 2 SNS Project, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA 3 Dept. of Physics, McMaster University, Hamilton LS8 $M1, Canada At first glance Tb2Ti2O7 and Tb2Sn2O7 should have very similar ground states. The Tb 3+ ion is the only magnetic species in the system and it makes up a sublattice of corner sharing tetrahedral. The Ising property of the spins and the antiferromagnetic coupling between them makes this system susceptible to geometric frustration. In fact, the Curie-Weiss constant for both compounds is approximately 15 K. However, no frozen state, either long range or short range has been observed in Tb2Ti2O7 whilst Tb2Sn2O7 enters a partially ordered state at ~0.9 K. I will report on recent neutron scattering data that reveals the differences between these two compounds. Reference: [1] J. S. Gardner, et al., Phys. Rev Lett., 82, 1012 (1999). [2] I. Mirebeau, et al., Phys. Rev Lett., 94, (2005). [3] B. D. Gaulin et al., Phys. Rev. B 84, (2011) 30

31 [O16] Electronic structure, superconductivity, and ferromagnetism in nickelate superlattices Myung Joon Han Department of Physics, Korea Advanced Institute of Science and Technology Our recent calculation results on two different nickelate superlattice systems will be presented; LaNiO3/LaAlO3 (or its variant) and LaNiO3/LaMnO3. For the former, the possibility of the cuprate-like superconductivity has been actively debated. Contrary to the previous theoretical suggestion, our DMFT (dynamical mean-field theory) and GW calculations do not support the one-band physics and high-temperature superconductivity in this type of heterostructure [1-3]. I will discuss the possible direction to search for those properties. For the latter, recent experiments report the ferromagnetism and exchange bias while the origin of them still remains unclear. Our first-principles calculation provides a clear understanding of this phenomenon; the charge transfer from Mn to Ni plays a crucial role in combination with the confinement effect [4]. Reference: [1] M. J. Han et al., Phys. Rev. Lett. 107, (2011) [2] M. J. Han and T. Kotani (in preparation) [3] H. -S. Kim and M. J. Han, arxiv: (submitted) [4] A. T. Lee and M. J. Han, Phys. Rev. B 88, (2013) 31

32 [O17] Superconductivity at 45 K in CaFeAs2 and CaFe2As2 with La doping M. Nohara Department of Physics, Okayama University, Japan We discovered superconductivity in novel 112-type (Ca1-xLax)FeAs2 [1]. The compound crystallizes in a monoclinic structure (space group P21), in which FeAs layers alternate with CaAs spacer layers such that monovalent arsenic forms zigzag chains. Superconductivity at 34 K was observed for the x = 0.1 sample, while trace superconductivity was observed at 45 K for the x = 0.21 sample, demonstrating the potential of the 112-phase for higher transition temperature. Another way to realize higher Tc is co-doping of lanthanum and phosphorus in 122-type CaFe2As2, which results in superconductivity at 45 K [2]. Superconductivity with a substantial shielding volume fraction was observed at 0.12 x 0.18 and y = 0.06 in Ca1-xLaxFe2(As1-yPy)2. In this doping range, the system exhibits crossover of the lattice collapse transition, which is characterized by the formation of As2 dimers between the adjacent FeAs layers. Reference: [1] N. Katayama, K. Kudo, S. Onari, T. Mizukami, K. Sugawara, Y. Sugiyama, Y. Kitahama, K. Iba, K. Fujimura, N. Nishimoto, M. Nohara, and H. Sawa, J. Phys. Soc. Jpn. 82, (2013). [2] K. Kudo, K. Iba, M. Takasuga, Y. Kitahama, J. Matsumura, M. Danura, Y. Nogami, and M. Nohara, Sci. Rep. 3, 1473 (2013). 32

33 [O18] Manifestation of magnetic quantum fluctuations in the dielectric properties Jae Wook Kim 1, Seunghyun Khim 1, Sae Hwan Chun 1, Y. Jo 2, L. Balicas 2, H. T. Yi 3, S.-W. Cheong 3, N. Harrison 4, C. D. Batista 5, Jung Hoon Han 6 and Kee Hoon Kim 1 1 CeNSCMR, Department of Physics and Astronomy, Seoul National University, Seoul , Republic of Korea 2 National High Magnetic Field Laboratory (NHMFL), Tallahassee, FL 32310, USA 3 Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Piscataway, NJ 08854, USA 4 NHMFL and Materials Physics and Applications - Condensed Matter and Magnetic Science (MPA-CMMS), Los Alamos National Laboratory (LANL), Los Alamos, NM 87545, USA 5 Theoretical Division, T-4 and Center for Nonlinear Studies, LANL, Los Alamos, NM 87545, USA 6 Department of Physics, Sungkyunkwan University, Suwon , Republic of Korea In metallic magnets, magnetic quantum fluctuation often leaves ubiquitous fingerprints in the transport properties by showing strange-metallic behavior or exhibiting anomalies related to the formation of an exotic order. Insulating magnets can in principle display such signatures in the dielectric properties; however, their inherently weak spin-lattice coupling has made the experimental observations challenging. Here, we present experimental and theoretical evidences for antiferromagnetic quantum fluctuations that manifest in the dielectric properties of the multiferroic Ba2CoGe2O7, wherein antiferromagnetism and ferroelectricity are strongly coupled. Upon application of a magnetic field (H) along the c-axis, the dielectric constant shows a characteristic power-law dependence near absolute zero temperature (T) at the critical field Hc = 37.1 T due to enhanced antiferromagnetic quantum fluctuations. When H is further increased beyond Hc, the T-dependence of the dielectric constant shows clear anomalies that are coupled to a crossover from a field induced polarized state to a gapped quantum paramagnet. We uncover theoretically that a linear relation between antiferromagnetic susceptibility and dielectric constant stems from the generic magnetoelectric coupling and directly explains the experimental findings, opening a new pathway for studying quantum critical phenomena in condensed matter. 33

34 [O19] High mobility, stability, and bipolar dopability of transparent perovskite semiconductor BaSnO3 Kookrin Char Center for Stronlgy Correlated Materials Research Dept. of Physics and Astronomy Seoul National University We have recently discovered that a perovskite BaSnO3 exhibits high mobility at room temperature when doped with La in the Ba sites. We will go over the mechanism for the high mobility, especially when compared with Sb doping in the Sn sites. We will discuss the large effect of threading dislocations on the mobility of epitaxial thin films on SrTiO3 substrates. In addition, a very stable oxygen stoichiometry in BaSnO3 system has been measured. Such high chemical stability promises a large potential for well-defined interface in heterostructures based on them. To demonstrate in this direction, we will present our current research efforts in pn-junctions and FETs based on the BaSnO3 system. Furthermore, 2DEG based on the BaSnO3 system can shed light on the exact mechanism of 2DEGs found at the interfaces of polar perovskites. We will report on our recent findings in this area as well. To further evaluate its potential for perovskite science, strongly correlated effects of 4d or 5d doping in the Sn sites are investigated. Due to high-mobility, chemical stability, and bipolar dopability, the BaSnO3 system promises a large potential to combine semiconductor and perovskite science and technology. 34

35 [O20] Photoinduced dynamics of spinel MnV2O4 as a spin-orbital coupled system Takuro Katsufuji Department of Physics, Waseda University, Tokyo , Japan Spinel MnV2O4 is a d 2 Mott insulator and exhibits a simultaneous magnetic and orbital ordering accompanied by a structural phase transition at 57 K. It is known that Al doping into the V site suppresses the orbital ordering and the structural phase transition but keeps the magnetic ordering almost unchanged. We studied the photoinduced dynamics of MnV2O4 and MnV1.8Al0.2O4 by pump-probe optical reflectivity measurements [1-3]. We found that the photoinduced dynamics of these compounds can be separated into three components, (1) the immediate (<1 ps) suppression of the Mott-excitation peak, (2) the melting of the orbital ordering, which results in the anisotropic change of the spectra, and (3) the melting of the magnetic ordering, which occurs several picoseconds after the photoirradiation. Such a relatively slow dynamics in the melting of the magnetic ordering is caused by the lower energy scale in magnetism compared with the transfer energy of the electrons dominating the suppression of the Mott excitation. Reference: [1] T Katsufuji et al., Phys. Rev. B 87, (2013). [2] A. Furuhashi et al., Phys. Rev. B 88, (R) (2013). [3] K. Takubo et al., Phys. Rev. B, in press. 35

36 [O21] Exotic electronic phases derived from semi-metals+ Hide Takagi Department of Physics, University of Tokyo, Hongo, Tokyo , Japan Max Planck Institute for Solid State Research, Stuttgart 70569, Germany Exotic electronic phases sometimes emerge in low carrier density semimetals, due to interplay of electrons and holes with Coulomb interaction and spin-orbit coupling. I will be talking about recent progress of our materials exploration, with emphasis on such exotic phases derived from semi-metals. The topics will include 1. excitonic transition in Ta2NiSe5, 2. a spin-orbital semimetal to a magnetic insulator transition in SrIrO3/SrTiO3 super-lattice and, if time allows, 3. three-dimensional Dirac electrons in anti-perovskites. +Work done in collaboration with A. Rost, T. Takayama, J.Matsuno, Y.Lu and D.Hirai 36

37 [O22] Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture Yong-il Shin Department of Physics and Astronomy, Seoul National University, Seoul, Korea When a spin-carrying particle slowly moves in a spatially varying magnetic field, it acquires the Berry phase which orginates from the geometric structure of the magnetic field. From this geometric phase, effective magnetic and electric forces can arise for the particle, even when it is electrically neutral. Recently, fictitious electromagnetism due to non-trivial spin textures has been studied in many areas of physics, e.g. to understand the anomalous Hall effect in magnetic materials and for spintronics applications. In this talk, I will introduce spinor Bose-Einstein condensates of neutral atoms with skrymion spin textures [1,2] and present our experimental observation of a geometric Hall effect in the spinor superfluid system [3]. When the condensate was driven in one direction to oscillate with respect to the spin texture, we observed the development of its transverse motion perpendicular to the driving direction and the effective field direction, demonstrating the existence of an effective Lorentz force in the system. Under a resonant drive, the center of mass of the condensate showed a circular motion around the center of the skyrmion spin texture and in particular, quantized vortices were nucleated in the circulating condensate. We observed that the growth rate of the vortex number increases with the effective field strength, i.e. the Berry curvature of the skyrmion spin texture. Reference: [1] J. Choi, W. J. Kwon, and Y. Shin, Phys. Rev. Lett. 108, (2012). [2] J. Choi et al., New J. Phys. 14, (2012). [3] J. Choi, S. Kang, S. W. Seo, W. J. Kwon, and Y. Shin, Phys. Rev. Lett. (to be published). 37

38 [O23] Strong increase of Tc of Sr2RuO4 under both tensile and compressive strain Clifford W. Hicks 1,2, Daniel O. Brodsky 2, Edward A. Yelland 2,3, Alexandra S. Gibbs, Jan A. N. Bruin, Keigo Nishimura 4, Shingo Yonezawa 4, Yoshiteru Maeno 4, Andrew P. Mackenzie 1,2 1 Max Planck Institute for Chemical Physics of Solids, Nothnitzer Strabe 40, Dresden 01187, Germany 2 Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS, United Kingdom 3 SUPA, School of Physics and Astronomy, and Centre for Science at Extreme Conditions, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, United Kingdom 4 Department of Physics, Graduate School of Science, Kyoto University, Kyoto , Japan The superconductor Sr2RuO4 has been thought for nearly twenty years to have a px+ipy order parameter, which would make Sr2RuO4 a two-dimensional electronic analogue of superfluid 3He, and would be a unique order parameter among known superconductors. But definitive demonstration has proved difficult. The crystal symmetry of Sr2RuO4 is tetragonal, and lifting the tetragonal symmetry by straining the crystal should lift the degeneracy between the px and py components. There should be a characteristic response at zero strain, where the order parameter switches between px and py. To test this hypothesis, we built apparatus capable of applying up to 0.25% compressive and tensile strain. Tc of Sr2RuO4 was found to increase strongly under both tensile and compressive strains along the crystallographic <100> directions, but is only weakly affected by <110> strains. As well as advancing our understanding of Sr2RuO4, this technique has potential applicability to a wide range of problems in sold-state physics. 38

39 [O24] Skyrmionics Maxim Mostovoy Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands Skyrmions are non-coplanar topological defects in ordered states with vector order parameters. Their non-trivial topology is a source of interesting physics. First introduced by T. H. R. Skyrme in his unified theory of baryons and mesons, they have been recently discussed as excitations in Quantum Hall ferromagnets and building blocks of crystal-like spin superlattices in complex magnets. Skyrmions have been observed in magnetic materials with a non-centrosymmetric crystal lattice, such as ferromagnetic metallic MnSi and ferromagnetic insulator Cu2OSeO3, using small-angle neutron scattering and Lorentz microscopy. I will discuss mechanisms for stability of skyrmions and new classes of magnetic materials in which these fascinating topological defects can be found. The Berry phase acquired by the wave function of the electron propagating through the noncoplanar spin configuration of skyrmion makes possible to identify skyrmion with a quantized flux of an effective magnetic field. This field gives rise to skew scattering of electrons off skyrmions and the resulting reaction force moves skyrmions along the direction of electrical current. Moving skyrmions induce effective electric fields which accelerate electrons. These effects give rise to complex coupled dynamics of electrons and skyrmions mediated by effective electromagnetic fields. It was recently shown that, like electrons, magnons also feel the effective magnetic field of skyrmions and that thermally-induced magnon currents induce spin torques that can set skyrmions into motion. This opens possibility to build all-spin analogues of electronic devices, in which skyrmions are controlled with magnon currents. I will discuss thermoelectric effects resulting from the coupled dynamics of electrons, magnons and skyrmions. 39

40 [O25] Dirac vs. Weyl in topological insulators: Adler-Bell-Jackiw anomaly in transport phenomena Ki-Seok Kim Department of Physics, POSTECH, Pohang , Korea Dirac metals (gapless semi-conductors) are believed to turn into Weyl metals when perturbations, which break either time reversal symmetry or inversion symmetry, are employed. However, no experimental evidence has been reported for the existence of Weyl fermions in three dimensions. Applying magnetic fields near the topological phase transition from a topological insulator to a band insulator in Bi1-xSbx, we observe not only the weak antilocalization phenomenon in magnetoconductivity near zero magnetic fields (B < 0.4 T) but also its upturn above 0.4 T only for E // B. This incompatible coexistence between weak antilocalization and negative magnetoresistivity is attributed to the Adler-Bell-Jackiw anomaly ( topological theta-term) in the presence of weak anti-localization corrections. 40

41 [O26] Quantum anomalous Hall effect in magnetically doped topological insulator Ke He State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing , China Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, The Chinese Academy of Sciences, Beijing , China Keywords: quantum anomalous Hall effect, topological insulator, magnetic doping Quantum Hall effect (QHE), one of the most important quantum phenomena in modern condensed matter physics, results from Landau quantization of a two-dimensional electronic system under strong magnetic field [1]. It has long been expected that QHE may occur without Landau levels so that neither external magnetic field nor high sample mobility is required for its studies and applications [2,3]. The QHE free of Landau levels can be realized in topological insulators (TIs) [3-7] with ferromagnetism as the quantized version of the anomalous Hall effect [3], i.e., the quantum anomalous Hall effect (QAHE). With molecular beam epitaxy [8], we have prepared thin films of Cr-doped (Bi,Sb)2Te3 TIs with well-controlled composition, thickness [8] and chemical potential [9], which exhibit long range ferromagnetism even in insulating phase [10]. In such thin films, we eventually observed the quantization of the Hall resistance at h/e 2 at zero field, accompanied by a considerable drop in the longitudinal resistance, which can completely vanish under a strong magnetic field. These observations unambiguously demonstrate the realization of the QAHE [11]. The observation of the QAHE not only concludes the decades-long search for zero field quantum Hall effect but represents a start point for exploration and applications of various topological quantum phenomena in the future. Reference: [1] S. M. Girvin, The Quantum Hall effect. Springer-Verlag, New York (1990). [2] F. D. M. Haldane, Phys Rev Lett 61 (1988) [3] N. Nagaosa, J. Sinova, S. Onoda, A. H. MacDonald, and N. P. Ong, Rev Mod Phys 82 (2010) [4] M. Z. Hasan and C. L. Kane, Rev Mod Phys 82 (2010) [5] X. -L. Qi and S. -C Zhang, Rev Mod Phys 83 (2011) [6] R. Yu, W. Zhang, H. Zhang, S. -C. Zhang, X. Dai, and Z. Fang, Science 329 (2010) 61. [7] K. Nomura and N. Nagaosa, Phys Rev Lett 106 (2011) [8] X. Chen, X. -C. Ma, K. He, J. -F. Jia, and Q. -K. Xue, Adv. Mater. 23 (2010) [9] J. Zhang, C. -Z. Chang, Z. Zhang et al., Nature Commun. 2 (2011) 574. [10] C. -Z. Chang, J. Zhang, M. Liu et al., Adv. Mater. 25 (2013) [11] C. -Z. Chang, J. Zhang, X. Feng, J. Shen et al., Science 340 (2013)

42 [O27] Odd interactions in quantum magnets and liquids Sasha Chernyshev UC Irvine I will discuss several scenarios in which interactions of excitations in quantum magnets and liquids give rise to unusual phenomena. Two of the principal cases concern the role of threeparticle interactions in the spectra of the non-collinear frustrated antiferromagnets and quantum liquids such as 4He. The other case study shows that the effect of random disorder may dwarf the conventional magnon-magnon scattering in a different class of antiferromagnets with XY anisotropy. Our results have strong support from the high-resolution neutron resonance spinecho experiments. Implications for the other systems are offered. 42

43 [O28] Observation of magnon decay and non-linear spin waves in LuMnO3 M. D. Le 1,2 1 Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea 2 Department of Physics and Astronomy, Seoul National University, Seoul, Korea We report the observation of magnon decay in a non-collinear antiferromagnet, LuMnO3, in line with recent theoretical work. This member of the rare earth hexagonal manganites possesses a triangular lattice of Mn3+ ions with spin S=2, which adopts the non-collinear 120 degrees order below TN=90K. At certain points in the Brillouin zone, the highest energy spin wave mode becomes exceptionally broad, indicative of its decay into two magnons. Additional features of the spin wave dispersion also point to a departure from linear spin wave theory. The system is further complicated by a trimerisation of the spins due to a giant offcentering of the Mn ions in the triangular plane, which allows short ranged correlations to persist well above TN. These features have, as yet, no complete theoretical treatment, but we will present new polarised inelastic scattering data which may shed light on the problem. 43

44 [O29] Defects in spin ice J. Goff RHL, London The idea of magnetic monopoles in spin ice has enjoyed much success at intermediate temperatures, but at low temperatures a description in terms of monopole dynamics alone is insufficient. Recently, numerical simulations were used to argue that magnetic impurities account for this discrepancy by introducing a magnetic equivalent of residual resistance in the system. Here we propose that oxygen deficiency is the leading cause of magnetic impurities in as-grown samples, and we determine the defect structure and magnetism using diffuse neutron scattering and magnetization measurements. From crystal field calculations we find that oxygen vacancies in spin ice cause the rare-earth anisotropy to change to easy plane. We further argue that these magnetic defects may be capable of trapping monopoles at sub-kelvin temperatures. 44

45 [O30] Many Body Physics in Graphene with ARPES A. Bostwick Advanced Light Source, Lawrence Berkeley National Laboratory, USA Graphene is a remarkable new electronic material with many unique properties. To realise its promise, it is essential to understand its the electronic structure. By measuring the spectral function of charge carriers using angle resolved photoemission from various type of graphene grown on SiC, we show that it is possible to develop a broad understanding of the electronic structure and many body interactions in graphene. We also show that the structure of the graphene and substrate on which it is placed play a key role in determining both the basic band structure and the strength and type of many body interactions. 45

46 [O31] Spin-orbital entangled jeff states in 4d and 5d transition metal systems Hosub Jin 1,2 1 Center for Correlated Electron Systems, Institute for Basic Science, Seoul, Korea 2 Department of Physics and Astronomy, Seoul National University, Seoul, Korea The discovery of the so-called jeff =1/2 state in the layered 5d transition metal oxide Sr2IrO4 has provided a new viewpoint in understanding the electronic and magnetic properties of the system containing large spin-orbit coupling [1]. The spin-orbital entangled nature of the jeff state can host various exotic phases with the help of electron correlations [2]. In this talk, we suggest that a series of 4d and 5d transition metal compounds, AM4X8, host the molecular form of the jeff state in their low energy electronic structures. Wide range of electron correlations are accessible by means of tuning the bandwidth under the external and/or chemical pressure, enabling us to investigate the interesting cooperation between SOC and electron correlations. On the way to search the possibility of the various emergent phases with respect to the competing electron correlation strength, we briefly elucidate the topological insulating phase and the complicated spin model in the weak and strong coupling limit, respectively. Reference: [1] B. J. Kim et al., Phys. Rev. Lett. 101, (2008). [2] For a review, see W. Witczak-Krempa, G. Chen, Y. B. Kim, and L. Balents, rxiv: (2013). 46

47 [O33] Neutron scattering studies of the kagomé lattice: quantum spin liquids and topological magnon bands Young Lee Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA I will describe experimental studies of new states of magnetism on the S=1/2 kagomé lattice, focusing on two materials: one with antiferromagnetic exchange and one with ferromagnetic exchange. Quantum spin liquids are new states of matter that are characterized by long-range entanglement and support exotic excitations. After 40 years since the original proposal for such a state by Anderson, these systems have only recently been realized in experiments. Herbertsmithite is a leading candidate for having a quantum spin liquid (QSL) ground state. A recent breakthrough in crystal growth has allowed us to uncover a hallmark signature of the QSL state. Inelastic neutron scattering measurements reveal that the spin excitations are fractionalized, a remarkable first. Additional measurements, made possible by the crystals, further corroborate the identification of a QSL. In contrast to the antiferromagnetic case, ferromagnetic moments on the kagomé lattice are not highly frustrated. Our neutron scattering measurements on Cu(1,3-bdc) confirm that the spins order at low temperatures. However, inelastic scattering reveals an interesting flat band in the magnon dispersion relations. Moreover, each band is separated by a gap from the other bands. I will discuss the role of the Dzyaloshinsky-Moriya interaction and the prospects of measuring new physics with topologically non-trivial magnon bands. Reference: 1. T.-H. Han, J.S. Helton, S. Chu, D.G. Nocera, J.A. Rodriguez-Rivera, C. Broholm, and Y.S. Lee, Nature 492, 406 (2012). 2. T.H. Han, S. Chu, and Y.S. Lee, Phys. Rev. Lett. 108, (2012). 47

48 [O34] Quantum and thermal criticality in magnets Christian Ruegg Laboratory for Neutron Scattering, Paul Scherrer Institute, Switzerland Department of Condensed Matter Physics, University of Geneva, Switzerland A quantum-- disordered ground state with a spin gap is separated in three-dimensional dimer antiferromagnets by a quantum critical point (QCP) from a phase with long-range antiferromagnetic order and finite ordering temperature [1]. While this QCP has been studied intensely in theoretical and numerical work by bond-operators and quantum Monte-Carlo, real materials in which it can be explored experimentally are rare. In the material TlCuCl3 this QCP was studied in great detail by neutron scattering and other techniques. These experiments provide unprecedented insights into quantum and thermal criticality and the elementary excitations near QCPs. A defining phenomenon is the emergence of longitudinal modes near the QCP [2], which are the Higgs excitations of dimer antiferromagnets [3], and their role in quantum and classical criticality [4]. Reference: [1] S. Chakravarty, B.I Halperin, and D.R. Nelson, Phys. Rev. B 39, 2344 (1989). [2] Ch. Ruegg et al., Phys. Rev. Lett. 100, (2008). [3] S. Sachdev and B. Keimer, Physics Today 64, 29 (2011) and arxiv: [4] P. Merchant et al., submitted. 48

49 [O35] Correlation effects in skew scattering mechanisms of Anomalous and Spin Hall Effects Timothy Ziman 1, 2 1 Institut Laue Langevin, Boîte Postale 156, Grenoble Cedex 9, France 2 LPMMC (UMR 5493), CNRS/ Université Joseph Fourier, Grenoble, France Skew scattering of electrons in ferromagnetic metals can produce the anomalous and spin Hall effects. The microscopic mechanism is normally considered to be either the intrinsic effect of the crystal lattice or scattering from impurities, with the spin-orbit interaction in each case providing the coupling between the spin and the displacement of the electrons. As this is a relativistic effect it is weak, and this is one of the obstacles to making and detecting spin currents. It is interesting to see whether effects of correlations can enhance the skew scattering and I will discuss this. In a ferromagnetic metal, scattering can also be from collective spin fluctuations, and we might expect these to be especially significant near the Curie temperature. Recently, with Bo Gu and S. Maekawa (ASRC, JAEA), we have extended Kondo's theory of the anomalous Hall effect to include short range spin-spin correlations and to find the spin hall coefficients. We find a novel relation of the transport coefficients to three- and four-spin correlations near the Curie temperature Tc the respective anomalous and spin hall coefficients. Our theory can be compared to recent experimental results by Wei et al [Nature Commun. 3, 1058 (2012)] for the ISHE in ferromagnetic alloys. Figure 1: Schematic behavior of the anomalous (left) and spin Hall resistances (right) around Tc. In each case the power-law divergence (dashed lines) of the corresponding non-linear susceptibility x 1 or x 2 is cut off by the finite Fermi surface. The different shapes (solid lines) of the anomalies reflect that the third order correlations vanish about Tc and the fourth order correlations change sign across Tc. 49

50 [O36] Quasiparticle carrier dynamics in graphene from first principles Cheol Hwan Park Department of Physics and Astronomy, Seoul National University, Seoul , S. Korea It is usually very important to understand how a charge carrier in real materials interacts with other charge carriers and lattice vibrations; these two effects, electron-electron and electronphonon interactions, respectively, largely determine the quasiparticle and transport properties of a material. In this presentation, we will show that some important aspects of quasiparticle dynamics in graphene can be described by first-principles calculations considering these two effects together. 50

51 [O37] Recent Thz results on quantum correlated matter P. Armitage Johns Hopkins University, USA The occurrence of novel quantum phenomena emergent on the longest length scales heightens the need for new experimental tools that probe finite, yet long time scales (compared to typical electronic ones). This talk will review recent advances in the area of THz spectroscopy and its application to exotic quantum states of matter. I will give examples on material systems as diverse as topological insulators, 1D quantum spin systems, and cuprate superconductors. A desire to characterize materials in a novel fashion and answer specific scientific questions is driving the technology forward, while new technology is changing the kinds of scientific questions we dare to ask. 51

52 [P1] XMCD study of the n-type high-tc ferromagnetic semiconductor (In,Fe)As:Be S. Sakamoto, 1 M. Kobayashi, 2 G. Shibata, 1 Y. Takahashi, 1 A. Fujimori, 1 T. Koide, 2 Y. Takeda, 3 Y. Saitoh, 3 H. Yamagami, 3,4 L. D. Anh, 5 P. N. Hai, 5 and M. Tanaka 5 1 Department of Physics, The University of Tokyo, Tokyo , Japan 2 IMSS, KEK, Ibaraki , Japan 3 Synchrotron Radiation Research Unit, JAEA, Hyogo , Japan 4 Department of Physics, Kyoto Sangyo University, Kyoto , Japan 5 Department of Electrical Engineering and Information Systems, The University of Tokyo, Tokyo , Japan (In,Fe)As is a new n-type ferromagnetic III-V semiconductor. By doping magnetic Fe atoms and Be double-donor atoms into InAs, n-type carrier-induced ferromagnetism was realized 1-3. In order to investigate the mechanism of the ferromagnetism, we performed x-ray magnetic circular dichroism (XMCD) measurements on samples with 5% Fe (TC =15K) and 10% Fe (TC above room temperature). Although the line shapes of the spectra resemble that of Fe metal, the ratio of the orbital moment to the spin moment estimated using sum rules was different from that of Fe metal, which rules out the possibility of Fe metal precipitation. The magnetic field (H) dependence of magnetization (M) deduced from the XMCD intensity is shown in Fig. 1. These curves were well fitted to a Langevin function due to superaparamagnetism (SPM) plus a linear function due to Curie-Weiss paramagnetism. From the fitting, the proportion of Fe atoms in the SPM clusters was estimated to be 30~40% for In0.9Fe0.1As and 50%~70% for In0.95Fe0.05As. The radius and the density of SPM clusters were comparable to the donor Bohr radius and the density of Be respectively and satisfy the criterion for metallic conductivity, which indicates the system is in the intermediate region between carrier-induced ferromagnetism and ferromagnetism due to bound magnetic polarons formed around the Be impurities. Fig. 1 M-H data for the sample with 10% Fe fitted to a Langevin function plus a linear function (solid lines). Linear parts are shown by dashed lines. [1] P. N. Hai et.al., Appl. Phys. Lett. 100, (2012). [2] P. N. Hai et.al., Appl. Phys. Lett. 101, (2012). [3] P. N. Hai et.al., Appl. Phys. Lett. 101, (2012). 52

53 [P2] The Magnetoelectric Effect in FeSb2O4 Single Crystals A. Iyama 1, Y. Wakabayashi 1, N. Hanasaki 2, and T. Kimura 1 1 Division of Materials Physics, Osaka University 2 Department of Physics, Osaka University The linear magnetoelectric (ME) effect has attracted attention over 50 years in which an electric polarization (magnetization) is linearly induced by an applied magnetic (electric) field. The ME property in FeSb2O4 (Space group P42/mbc) was measured with using polycrystalline samples [1] after a neutron scattering experiment which proposed that the magnetic symmetry of FeSb2O4 below the Neel temperature TN ~ 46 K is Pmc21, allowing the linear ME effect [2]. However, there has been no report on the ME property in FeSb2O4 single crystals. Thus, the ME effect in the single-crystalline samples grown by the hydrothermal method is investigated [3]. We have examined the dielectric constant and the electric polarization in various directions of a magnetic field relative to the crystallographic axes. The anisotropy of the ME effect was observed below TN. The observed ME property is consistent with the magnetic structure proposed by the former neutron scattering study with the polycrystalline samples. It is also found that the spontaneous electric polarization in the absence of a magnetic field is negligibly small although the proposed magnetic structure allows a finite spontaneous polarization. It will be discussed how the observed ME property can be understood. Figure: Obtained single crystals of FeSb2O4 by the hydrothermal method. [1] G. Gorodetsky, M. Sayar, and S. Shtrikman, Mat. Res. Bull. 5, 253 (1970). [2] J. A. Gonzalo, D. E. Cox, and G. Shirane, Phys. Rev. 147, 415 (1966). [3] A. Iyama, Y. Wakabayashi, N. Hanasaki, and T. Kimura, accepted for publication in Jpn. J. Appl. Phys. 53

54 [P3] Soft-X-ray Resonant Inelastic X-ray Scattering for Vanadium Oxides H. Fujiwara 1, Y. Nakata 1, S. Naimen 1, Y. Nakatani 1, J. Miyawaki 2,3, S. Niwa 2, H. Kiuchi 4, A. Tanaka 5, J. Denlinger 6, J. W. Allen 7, S.-K. Mo 6,7,8, P. Metcalf 9, M. Imai 10, K. Yoshimura 10, T. Kiss 1, A. Sekiyama 1, Y. Harada 2,3 and S. Suga 11 1 Graduate School of Engineering Science, Osaka University, , Osaka, Japan 2 Institute for Solid State Physics (ISSP), University of Tokyo, , Chiba, Japan 3 Synchrotron Radiation Research Organization, University of Tokyo, , Hyogo, Japan 4 Department of Applied Chemistry, University of Tokyo, , Tokyo, Japan 5 Department of Quantum Matters, ADSM, Hiroshima University, , Hiroshima, Japan 6 Advanced Light Source, Lawrence Berkeley National Laboratory, CA 94720, Berkeley, USA 7 Randall Laboratory of Physics, University of Michigan, Ann Arbor, 48109, Michigan, USA 8 Department of Physics, Stanford University, Stanford, 94305, California, USA 9 Department of Physics, Purdue University, West Lafayette, 47907, Indiana, USA 10 Department of Chemistry, Graduate School of Science, Kyoto University, , Kyoto, Japan 11 Institute of Scientific & Industrial Research, Osaka University, , Osaka, Japan Strongly correlated vanadium oxides VO2 and V2O3 show the first order metal-insulator transition (MIT) accompanying with structural transition. The mechanism of MIT has been discussed from both modern experiments and many body theories. Recent combination studies of the polarized soft-x-ray absorption spectroscopy and the configuration interaction theory reports the drastic switching for the orbital occupation of the V 3d electron across MIT of VO2 [1,2]. This finding strongly suggests the electron correlation assisted Peierls transition mechanism. Meanwhile V2O3 is a paradigmatic example of Mott-Hubbard metal-insulator transition (MH- MIT) materials with a very rich phase diagram as a function of temperature, pressure and Ti- or Cr-doping [3]. The switching of the orbital population of the V 3d states has been also discussed by the polarized XAS [4]. To reveal the mechanism of MIT, we have performed high-resolution resonant inelastic X-ray scatting for VO2 and (V1-xCrx)2O3 (x = 0, 0.015). This spectroscopy is powerful to probe the electron excitation from occupied d states to the unoccupied side, which is called d-d excitation. In the insulator phase of VO2, RIXS spectra show the strong polarization dependence for the peak due to the d-d excitations, while in the high temperature metallic phase the spectra are isotropic. These finding suggests the polarization dependence of RIXS is powerful probe for the electronic structure with switching of the orbital occupation. In the presentation, we also discuss the d-d excitations and low energy excitation for (V1-xCrx)2O3. [1] M. W. Haverkort, et al., Phys. Rev. Lett. 95, (2005). [2] T. C. Koethe, et al., Phys. Rev. Lett. 97, (2006). [3] D. B. McWhan, et al., Phys. Rev. Lett. 23, 1384 (1969). [4] J.-H. Park, et al., Phys. Rev. B 61, 11506(2000). 54

55 [P4] Electrostatic Switching of In-plane Anisotropic Superconductivity in YBa2Cu3O7-σ/ BiFeO3 Heterostructure Yen-Lin Huang 1, Vu- ThanhTra 2, Heng-Jui Liu 1, Long-Yi Chen 3, Shih-Ting Guo 4, Wei-Li Lee 4, Chih-Wei Luo 3, Jiunn-Yuan Lin 2 and Ying-Hao Chu 1 1 Department of Materials Science and Engineering, National Chiao Tung University, HsinChu, 300, Taiwan 2 Institute of Physic, National Chiao Tung University, HsinChu, 300, Taiwan 3 Department of Electrophysics, National Chiao Tung University, HsinChu, 300, Taiwan 4 Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan yenlin.jack.huang@gmail.com Strongly correlated electronic systems exhibit a variety of physical properties, such as superconducting, colossal magnetoresistance, metal-insulator transition. To study the competition between different ground states in the phase diagram, changing the doping level by field-effect-transistor is a prevalent method. However, this technique has been limited by the conducting sample known as the dielectric breaking-down, and it is also difficult to achieve the modulation of electrostatic boundary in nano-scale. Here, we demonstrate a correlation between the periodic domain structure of multiferroic BiFeO3 thin films and the anisotropic superconducting of YBa2Cu3O7--σ/BiFeO3 heterostructures. Two types of periodic domain structures in BFO 71 o and 109 o are used to tune the superconductor, YBCO, and an anomalous superconducting behavior, which shows different transition regions parallel or perpendicular to the domain walls of BFO respectively, is observed. The superconducting transition region is much broader when the current goes perpendicularly to the domain walls in BFO than parallel. The difference of Tc is about 40 K, in other words the YBCO shows one dimensional superconducting behavior within 40 K. Two possible interpretations are discussed: either the magnetic field, which is created by the uncompensated spin in the domain walls of BFO, or the second phase segregation, which could be induced by antiferromagnetism in BFO. In concluding, the periodically long-term domain structures of BFO could provide a path way to manipulate high temperature superconductivity, and the in-plane anisotropic superconducting could intrigue to a variety of studies and applications. 55

56 [P5] The Electrical Modulation of Interface Conduction at the BiFeO3- CoFe2O4 Oxide Interface Ying-Hui Hsieh 1, Jia-Ming Liou 2, Chia-Ying Shen 1, Yi-Chun Chen 2, and Ying-Hao Chu 1 1 Department of Materials Science and Engineering, National Chiao Tung University Rm. 709, Eng. Bd. VI, No.1001, Dasyue Rd., East Dist., Hsinchu City 30010, Taiwan (R.O.C.) 2 Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan No.1, Dasyue Rd., East Dist., Tainan City 70101, Taiwan (R.O.C.) Phone: ext joe0203.mse96@g2.nctu.edu.tw The two features of oxide interface produce various new phenomena and functions the destruction of I symmetry and the effects of electron correlation en-hanced by 2 dimensions which are hard to attain at the bulk materials[1]. In addition, the interaction among degrees of freedom spin, charge and orbital in electrons produce many electronic phases, which cause new device functions, such as sensing and non-volatile memory, providing the possibility for next-generation devices[2]. Some new observation was made on the ef-fects of the degree of freedom at the oxide interfaces: 2 dimensional electron gas at the LaAlO3-SrTiO3 het-erointerface[3], the hetero-interface (Figure 1.(a)), local conductivity at the BiFeO3 domain wall[4], and the ho-mo-interface(figure 1.(b)). These complex oxide inter-faces create an arena to discover novel phenomena. This study researches an interface which is seldom noticed before, that is, the interface formed by the self-assembled nanostructures (Figure 1.(c)). As a result of the competition of the surface energies, the phases separate spontaneously in the self-assembled nanostruc-ture system during the growth process[5]. The BiFeO3 (BFO)-CoFe2O4 (CFO) was adapted as a model system to carry out the systematic study on the BFO-CFO ver-tical interface. Figure 1. Three kinds of oxide interfaces (a) Het-ero-Interface (b)homo-interface (c) Tubular-Interface In order to investigate the electrical properties of the tubular oxide interface, we performed conductive atomic force microscopy (C- AFM) at different temperatures. The local conduction was found at the BFO-CFO vertical interface and the origin of the conduction is identified as a result of the oxygen vacancies accumulating at the interface[6]. In addition, we have observed that this conduction can be modulated with a DC bias. This phenomenon can be under-stood owing to the movement of oxygen vacancies driven by the applied bias. The bias cause the oxygen vacancies either accumulate or deplete to the metal contact tip, which in turn affect the resistance at the tubular interface deciding the whether current can pass or not. Such a behavior is very close to a memristor, which can be used to design new practical devices. Our findings suggest the tubular oxide interface can not only be the medium to the coupling be-tween phases, but also be a new state of the matter, which demonstrates a novel concept on oxide interface design and opens a pathway alternative for the explorations of diverse functionalities in complex oxide interfaces. 56