Novel Magnetic Order and Excitations in the Pseudogap Phase of HgBa 2 CuO 4+

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1 Novel Magnetic Order and Excitations in the Pseudogap Phase of HgBa 2 CuO 4+ Martin Greven (University of Minnesota) FRM-II

2 Our Group & Collaborators Dr. Neven Barišić (Stuttgart U.) Guillaume Chabot-Couture Dr. Yong-Chan Cho (Pusan National U.) Roberta Edwards Dr. Jason Hancock (U. of Geneva) Patrick Harazin Yuan Li Wesley Lim Eugene Motoyama Owen Vajk (U. Missouri) Inna Vishik Dr. Guichuan Yu Prof. Xudong Zhao (Jilin U.) Collaborators: V. Balédent, P. Bourges, B. Fauqué, and I. Sidis (Laboratoire Léon Brillouin, France) K. Hradil (U. Göttingen, Germany) and R. Mole (FRM-II, Germany) P. Steffens (ILL, France)

3 Outline Introduction HgBa 2 CuO 4+ (Hg1201) Sample characterization Zhao et al., Adv. Mat. 18, 3243 (2006); Barišić et al., PRB 78, (2008) Magnetic resonance; universality Yu et al., arxiv: ; arxiv: Hidden magnetic order Li et al., Nature 455, 372 (2008) Novel magnetic excitations Li et al., unpublished

4 INTRODUCTION Model Compounds HgBa 2 Ca n-1 Cu n O y Eisaki et al., PRB (2004)

5 INTRODUCTION Crystal Growth Image Furnace Growth - we operate three image furnaces -La 2 Cu 1-z (Zn,Mg) z O 4, La 1-x Sr 1+x MnO 4, Nd 2-x Ce x CuO 4, Bi 2 (Sr,La)CuO 6+, Melt Growth of HgBa 2 CuO 4+ - simple tetragonal structure - single crystals of record size (up to 0.2 cm 3 ) Zhao et al., Adv. Materials (2006)

6 INTRODUCTION Neutron Scattering: Cross Section Cross section proportional to S(Q,ω), the Fourier transform of the pair correlation function Dynamic structure factor Momentum transfer Q = ki kf and energy transfer ħω = Ei Ef

7 INTRODUCTION Neutron Scattering: Cross Section Cross section proportional to S(Q,ω), the Fourier transform of the pair correlation function Dynamic structure factor Momentum transfer Q = ki kf and energy transfer ħω = Ei Ef Neutrons interact with nuclei and with magnetic densities Elastic scattering (ω=0) due to static structure; inelastic scattering due to dynamic excitations

8 INTRODUCTION Neutron Scattering: Triple-Axis Spectrometer Cross section proportional to S(Q,ω), the Fourier transform of the pair correlation function Dynamic structure factor Momentum transfer Q = ki kf and energy transfer ħω = Ei Ef Geometry for triple-axis neutron scattering: monochromator analyzer E i, k i E f, k f source detector sample

9 SAMPLE CHARACTERIZATION Oxygen/Hole-Doping Control Different anneal conditions yield samples over wide doping range: Under-doped Optimally-doped Over-doped Barišić et al., PRB (2008)

10 SAMPLE CHARACTERIZATION Phase Diagram Comparison with previous results for polycrystalline samples Yamamoto et al., PRB (2000)

11 SAMPLE CHARACTERIZATION Resistivity for Three Crystals with T c =81K 3 Different Crystals Normalized at 400 K T* m cm) Barišić et al., PRB (2008)

12 Outline Introduction HgBa 2 CuO 4+ (Hg1201) Sample characterization Magnetic resonance; universality Yu et al., arxiv: ; arxiv: Hidden magnetic order Novel magnetic excitations

13 MAGNETIC RESONANCE Sample Characterization 24 crystals volume ~ 0.5 cm 3 mosaic ~ 1.2º onset T c ~ 96 K (nearly optimally doped) Yu et al., arxiv:

14 MAGNETIC RESONANCE Large Resonance Energy: E r = 56 mev Ratio E r /k B T c ~ 7, not universal Yu et al., arxiv:

15 MAGNETIC RESONANCE Temperature Dependence T c Yu et al., arxiv:

16 MAGNETIC RESONANCE Resonance Energy vs. T c E r = 5.8 k B T c Yu et al., arxiv:

17 MAGNETIC RESONANCE Resonance Energy vs. T c Yu et al., arxiv:

18 MAGNETIC RESONANCE References YBCO (odd) Rossat-Mignod et al., Physica C (1991); Mook et al., PRL (1993); Fong et al., PRL (1995); Bourges et al., PRB (1996); YBCO, Ca-YBCO (odd & even) Bi2212 (odd) Bi2212 (odd & even) Tl2201 LSCO Hg1201 PLCCO Dai et al., PRB (2001); Stock et al., PRB (2004) Pailhès et al., PRL (2003), PRL(2004), PRL (2005); Fong et al., PRB (2000) Fong et al., Nature (1999); He et al., PRL (2001) Capogna et al., PRB (2007) He et al., Science (2002) Christensen et al., PRL (2004); Lipscombe et al., PRL (2007) Our work (arxiv: ) Wilson et al., Nature (2006) NCCO Our work (arxiv: ) UPd 2 Al 3 Sato et al., Nature (2001) CeCoIn 5 Stock et al., PRL (2008) Ba 0.6 K 0.4 Fe 2 As 2 Christianson et al., Nature (2008)

19 MAGNETIC RESONANCE Resonance Energy vs. Superconducting Gap E r = 2 E r = 0.64*(2 ) Yu et al., arxiv:

20 MAGNETIC RESONANCE Gap vs. Hole-Doping Ozyuzer et al., Physica C (1999) Momono et al., Mod. Phys. Lett. (2003) Miyakawa et al., PRL (1998); (1999) Sutherland et al., PRB (2003) Hawthorn et al., PRB (2007) McElroy et al., PRL (2005) Lee et al., Nature (2006) Gomes et al., Nature (2007) Alldredge et al., Nature Physics (2008) Photoemission - Bi2212: Tanaka et al., Science (2006) Lee et al., Nature (2007) Photoemission - LSCO: Yoshida et al., arxiv:

21 MAGNETIC RESONANCE Resonance Energy vs. Superconducting Gap Yu et al., arxiv:

22 Outline Introduction Hole-Doped HgBa 2 CuO 4+ (Hg1201) Sample characterization Magnetic resonance; universality Hidden magnetic order Li et al., Nature 455, 372 (2008) Novel magnetic excitations Li et al., unpublished

23 HIDDEN MAGNETIC ORDER Phase Diagram: Hole-Doped Curpates Pivotal issues: Nature of pseudogap? Magnetism and high-tc Pairing glue? Minimal model?

24 HIDDEN MAGNETIC ORDER Polarized Neutron Scattering Data taken on cold 3-axis instrument (4F1) at LLB; Ei = 14.7 mev Q = ki kf ; ħω = Ei Ef = 0 Polarization analysis: magnetic vs. nuclear scattering Measure moment component perpendicular to both Q and polarization P For P Q, magnetic scattering occurs in spin-flip channel only PG filter spin flipper Helmholtz coils (or CryoPAD) Heusler monochromator (down-spin) guide field (~10 Oe) detector Heusler analyzer (up-spin)

25 HIDDEN MAGNETIC ORDER Prior Result for YBa 2 Cu 3 O 6+ (YBCO) QuickTime and a TIFF (LZW) decompressor are needed to see this picture. Most data taken with P Q = (1 0 1) Relatively weak nuclear Bragg peak Non-spin-flip (NSF) scattering: nuclear Spin-flip (SF): magnetic + nuclear leakage Flipping Ratio (FR) = NSF/SF of ~ 50 Order preserves translational symmetry Fauqué et al., PRL (2006)

26 HIDDEN MAGNETIC ORDER Order also seen in Hg1201

27 HIDDEN MAGNETIC ORDER Magnetic Order and DC Resistivity Magnetism due to orbital currents! Li et al., Nature (2008)

28 HIDDEN MAGNETIC ORDER Universal Phase Diagram YBa 2 Cu 3 O 6+ (YBCO): Fauqué et al., PRL (2006), Mook et al., PRB (2008) T c (p) for Hg1201: Yamamoto et al., PRB (2000) T c (p) for YBCO: Liang et al., PRB (2006) Li et al., Nature (2008)

29 HIDDEN MAGNETIC ORDER Possible Scenario: Charge-Current Loops Zero FM moment I (1/2, 1/2, l) = 0 I (1, 0, l) 0 Intensity dependence Simple model gives: I (1,0,0) : I (1,0,1) : I (1,0,2) 2.5 : 1.7 : 1 I (1,0,1) : I (2,0,1) 8 : 1 Moment direction Variant of planar current-loop order proposed by Varma, PRB (1997); PRB (2006) Out-of-plane currents/extended Hubbard model considered by Weber et al., PRL (2009)

30 Conclusions Breakthrough in crystal growth Zhao et al., Adv. Materials (2006) Doping control, quantitative transport Barišić et al., PRB (2008) Observed magnetic resonance: E r 7 k B T c for p 0.16 Yu et al., arxiv: Universality: E r 2 Yu et al., arxiv: Universal hidden magnetic order in pseudogap phase Li et al., Nature (2008) Novel magnetic excitations in pseudogap phase Li et al., unpublished