November 16, 2015 ISS 2015 (Funabori, Tokyo) Road to Higher T. S. Uchida, Univ of Tokyo, 2. AIST, Tsukuba, 3. IOP-CAS, Beijing

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1 Road to Higher T November 16, 2015 ISS 2015 (Funabori, Tokyo) S. Uchida, 1 Univ of Tokyo, 2 AIST, Tsukuba, 3 IOP-CAS, Beijing T c stopped rising in 1993 (more than 20 years silence ), but signatures of higher T c s have come out quite recently: (1) Monolayer FeSe on SrTiO 3 (2) Sulfur Hydride under 200 GPa pressure (3) YBCO under THz laser pulse excitation - Overview of recent discoveries of higher-t c signatures under extreme conditions 1

2 200 History of T c : The longest silence K@30GPa 100 HgBaCaCuO 1988 TlBaCaCuO 1993 YBaCuO K 2014 LaBaCuO Nb 3 Ge BaKBiO 3 30K K SmFeAsO 55 K MgB 2 39 K LaFeAsO LaFePO Year 2

3 Road to Higher T c Chapter 2: Phonon-SC Chapter 3: High-T c cuprates Chapter 4: Fe-based SC

4 200 Break of T c Silence?: (1) Fe-SC SmFeAsO 55 K 1uc-FeSe on STO ~ 65 K LaFeAsO LaFePO year 4

5 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April FeSe Monolayer on a SrTiO3 Substrate Tc = 65±5 K Se cf. Tc = 8 K for bulk FeSe Fe Se SrTiO3 T = K (?) Review I. Bozovic &c C. Ahn, Nature Phys. 10, 892 (2014). Dung-Hai Lee, arxiv: (2015). Q.Y. Wang et al., Chin. Phys. Lett. 29, (2012). S. He et al., Nature Mater. 12, 605 (2013). J.J. Lee, Z.-X. Shen et al., Nature 515, 245 (2014). J.F. Ge, Q.K. Xue, J.F. Jin et al., Nature Mater. 14, 285 (2015). Y. Miyata et al., Nature Mater. 14, 775 (2015), and many others 5

6 200 (2) H 2 S (H 3 S) at P~200 GPa 203 K H 3 S@P 100 Nb 3 Ge 23 K BaKBiO 3 30 K MgB K year

7 Sulfur GPa : Phonon-SC (?) A.P. Drozdov, M.I. Eremets, I.A. Troyan, arxiv: A.P. Drozdov, M.I. Eremets, I.A. Troyan, V. Ksenofontv & S.I. Shylin, Nature 525, 73 (2015). (Max Planck, Mainz) T c = 203 K cf. 210 GPa Theoretical prediction: (T c = 29 K), Crystal volume V/V 0 ~ 1/5 P-induced metallization of dense (H 2 S) 2 H 2 with high-t c superconductivity D. Duan et al., Sci. Reports 4, (2014). (Jilin Univ., Changchun) 7

8 200 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April (3) Transient RTS in YBCO K Photoexcited YBCO 100 HgBaCaCuO 1988 TlBaCaCuO 1993 YBaCuO K 2014 LaBaCuO Year 8

9 Optically Induced SC (?) at T 300K in YBCO S. Kaiser, A.Cavalleri et al.; PRB 89, (2014). W. Hu, A. Cavalleri et al.; Nat. Phys. 13, 705 (2014). (Max Planck, Hamburg) T c ~ 350 K 9

10 200 Break of T c Silence?: (1) Fe-SC SmFeAsO 55 K 1uc-FeSe on STO ~ 65 K LaFeAsO LaFePO year 10

11 FeSe Monolayer on a SrTiO 3 Substrate T c T c = 108 K? S. He, Q-K. Xue, X.J. Zhou et al., Nature Mater. 12, 605 (2013). Z. Zhang, D.-L. Feng, Yayu Wang et al., arxiv: Science Bulletin 60 (14), (2015) J.F. Ge, Q.K. Xue et al., Nature Mater. 14, 285 (2015). 11

12 Thickness dependence of T c for FeSe films on STO FeSe FILMS on STO (updated as of Nov.13, 2015) Bi FILMS 4.36 Thinner thickness from s (T) Å C. Tang, Q.-K. Xue et al., Phys. Rev. B 92, (2015). Y. Miyata, T. Takahashi et al., Nature Mater. 14, 775 (2015). C.H.P. Wen, D.-L. Feng et al., arxiv: D.B. Haviland, Y. Liu & A.M. Goldman, Phys. Rev. Lett. 62, 2180 (1989). 12

13 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April Interface Effects in FeSe Monolayer on STO Se Fe Se SrTiO3 Se O Ov Review O Interface effects : 1) An additional pairing channel from a coupling with the bond-stretching O vibrations (Ω0 ~ 100 mev) in SrTiO3. 2) Electron transfer (doping) from O vacancies in STO O Ti Tc = 65±5 K Dung-Hai Lee, arxiv: ; Chin. Phys. B24, (2015). 13

14 200 (2) T c ~203 K: Phonon-SC H 3 S@200 GPa 203 K 100 Nb 3 Ge 23 K BaKBiO 3 30 K MgB 2 39 K year 14

15 T c = 203 K Superconductivity in Sulfur Hydride (H 3 P=200 GPa Resistance Magnetization/ Meissner A.P. Drozdov, M.I. Eremets, I.A. Troyan, V. Ksenofontv & S.I. Shylin, Nature 525, 73 (2015). 15

16 T c bound (ceiling) of phonon SC (McMillan-Allen-Dynes) ħ<ω> k B T c Weak to moderate el-ph coupling: k B T c ~ ħω 0 e -1/λ For very large Ω 0 and moderate λ, no T c ceiling as long as ħω 0 E F Hydrogen Dominant Metallic Alloys: HTS? N.W. Ashcroft, Phys. Rev. Lett. 92, (2004). Strong el-ph coupling: For large λ; T c ~ λ 1/2 No T c ceiling as long as a lattice instability can be avoided. 16

17 No T c bound for phonon SC (?) McMillan-Allen-Dynes (assuming µ = ) GPa, T c ~ 750 K Ω 0 = (K/ M) 1/2 ~ 400 mev, <ω> 2300 Κ, λ 3 3. H GPa, T c ~ 200 K J.M. McMahon & D.M. Ceperley, Phys. Rev. B 84, (2011). Ω 0 = (K/ M) 1/2 ~ 200 mev, <ω> 1300 Κ, λ MgB 0 Pa, T c ~ 40 K Ω 0 = (K/ M) 1/2 ~ 80 mev, <ω> 600 Κ, λ 1 1. doped BaBiO 3, T c ~ 30 K Unstable against CDW 17

18 (3) Resonant excitation of 20THz apical-o phonon in underdoped YBCO S. Kaiser, A.Cavalleri et al.; PRB 89, (2014). apical-o 20 THz ~ 80 mev pulses of ~300 fs duration apical-o 18

19 Transient RTS ( T c > 300 K) in YBCO Emergence of Josephson plasma in several picosec. duration S. Kaiser, A.Cavalleri et al.; PRB 89, (2014). YBa 2 Cu 3 O 6.45 T c = 35 K YBa 2 Cu 3 O 6.45 T c = 35 K ρ a ρc Josephson Plasma 0 19

20 Consequences of Broken Gauge Symmetry: SC Yoichiro Nambu Emergence: 1. Stiffness : Zero resistance & Meissner effect 2. Topological defects: Vortex 3. Collective mode: Anderson-Higgs 20

21 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April Broken Gauge Symmetry Collective mode Reflectivity spectrum of a conventional superconductor ω ωp Reflectivity E2 = (mc2)2 + p2c2 Anderson-Higgs mechanism: Long-range Coulomb 0 ωp2 = ne2/m* ε Plasma mode Nambu-Goldstone q m=0 ωp Photon energy ħω (ev) 4.0 Indistiguishable from the spectrum P.W. Anderson: Phys. Rev. 130, 439 (1963) in the normal state (T > Tc) P.W. Higgs: Phys. Rev. Lett. 13, 508 (1964) 21

22 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April Josephson Plasma Mode: c-axis high-tc cuprates Interlayer phase coherence is established at Tc: Forming a Josephson-junction array along the c-axis c c ωpj: Josephson plasma frequency ωpj < 2 0 ωpj2 = ne2/m* ε CuO2 CuO2 CuO2 m* K. Tamasaku, Y. Nakamura & S. Uchida, Phys. Rev. Lett. 69, 1455 (1992). O.K.S. Tsui, N.P. Ong et al., Phys. Rev. Lett. 73, 724 (1994). 22

23 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April Transient RTS ( Tc > 300 K) in YBCO Excitation of large amplitude c-axis apical-o phonon S. Kaiser, A.Cavalleri et al.; PRB 89, (2014). YBa2Cu3O6.45 Tc = 35 K Tc* Josephson Plasma Tc 23

24 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April More than establishment of interlayer coherence Temperature T (K) 400 Tc* PG TN AF T* Pairs without interlayer phase coherence Establishment of interlayer phase coherence Tp Tc 0.1 FL d-sc 0.2 Hole doping p 0.3 The emergence of a plasma edge at T where no signature of QCPin? equilibrium preformed pairs is observed 24

25 What is the mechanism of driving pair formation and enhancing the interlayer coherence? Excitation of large amplitude apical-o displacement: Transiently creates a displaced crystal structure with atomic positions more favorable for higher T c... Reduction of the interbilayer fluctuations by a LASER (parametric) cooling Dynamically stabilized SC state? N. Peter Armitage, Nature Mater. 13, 665 (2014). A Kapitza pendulum 25

26 Non-Equilibrium Lattice Distortions Resonant excitation of apical-o vibrations by c-axis polarized 20TH Z light pulse transient lattice distortions R. Först et al.; PRB 90, (2014). R. Mankowsky et al.; Nature 516, 71(2014). CuO 2 Y CuO 2 apical- O enhanced buckling shorter apical-o distance CuO 2 CuO 2 26

27 IEEE/CSC & ESAS SUPERCONDUCTIVITY NEWS FORUM (global edition), April More than establishment of interlayer coherence Temperature T (K) 400 Tc* PG TN AF T* Tp: Pairs without interlayer phase coherence Establishment of interlayer phase coherence Tc 0.1 FL d-sc 0.2 Hole doping p 0.3 The emergence of a plasma edge at T where no signature of QCPin? equilibrium preformed pairs is observed 27

28 200 Break of T c Silence in 2014? K@30GPa 350 K 203 K 100 HgBaCaCuO 135 K 1988 TlBaCaCuO YBaCuO K SmFeAsO 55 K 2001 MgB LaBaCuO 2 39 K BaKBiO 3 LaFeAsO Nb 3 Ge 23 K 30 K LaFePO Year 28