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FLEX Study of b ’-(ET) 2 AuCl 2

FLEX Study of b ’-(ET) 2 AuCl 2

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FLEX Study of b ’-(ET) 2 AuCl 2

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  1. FLEX Study of b’-(ET)2AuCl2 Hiori Kino (National institute for materias science) Hiroshi Kontani (Nagoya Univ.) Tsuyoshi Miyazaki (National institute for materials science)

  2. Motivation b’-(ET)2ICl2 b’-(ET)2AuCl2* Structure ambient pressure under applied pressure --- Almost the same ET stacking--- insulator AF insulator superconductivity insulator Why? *Taniguchi, et al., JPSJ 74, 1370 (2005).

  3. Electronic structure(first-principles study by Miyazaki et al,) Dimensionality of Fermi surfaces b’-(ET)2ICl2 b’-(ET)2AuCl2 Quasi-1D Quasi-1D Ambient pressure Applied pressure 2D 3D

  4. Fermi surfaces (tight binding fit) 4GPa 0GPa 8GPa c* b* a* 12GPa 16GPa 20GPa

  5. Q? higher dimensionality of Fermi surface stabilize AF phase in b’-(ET)2AuCl2? • Methods: • Hamiltonian: • tight binding model (ET dimer model) • effective on-site (intra-dimer) Coulomb interaction • Perturbation theory: • FLEX-approximation

  6. Results TN Ueff=0.5eV No SC phase

  7. Discussion c* b’-(ET)2AuCl2 b* (p,p,0) a* Temperature Enhance (2D→3D) TN Fermi surface nesting? U? Suppress (→1D) AF No SC phase Pressure b’-(ET)2ICl2 Temperature Suppress (→1D) 2D AF Pressure SC

  8. Discussion (2) temperature TN interlayer dimensionality TN Pressure AuCl2 TSC Pressure ICl2 intralayer dimensionality

  9. Fermi surfaces (extended zone) 12GPa 20GPa

  10. Summary • b’-(ET)2AuCl2 • AF phase is stabilized under applied pressures. • Reason: • Higher-dimensionality • U → better FS nesting

  11. Fermi surfaces (2D, b-axis-off) c* a* 0GPa 4GPa 8Gpa 20GPa 12GPa 16GPa →Destabilize AF?