FLEX Study of ’-(ET)2AuCl2
Hiori Kino (National institute for materias science)Hiroshi Kontani (Nagoya Univ.)
Tsuyoshi Miyazaki (National institute for materials science)
Motivation
’-(ET)2ICl2 ’-(ET)2AuCl2*
Structure
ambient pressure
under applied pressure
--- Almost the same ET stacking---
AF insulator insulator
superconductivity insulator
Why?*Taniguchi, et al., JPSJ 74, 1370 (2005).
Dimensionality of Fermi surfaces
Quasi-1D Quasi-1D
Electronic structure (first-principles study by Miyazaki et al,)
’-(ET)2ICl2 ’-(ET)2AuCl2
Ambient pressure
Applied pressure 3D2D
0GPa 4GPa 8GPa
12GPa 16GPa 20GPa
Fermi surfaces (tight binding fit)
a*
c*
b*
Q?
higher dimensionality of Fermi surface stabilize AF phase in ’-(ET)2AuCl2?
Methods:Hamiltonian:•tight binding model (ET dimer model) •effective on-site (intra-dimer) Coulomb interaction
Perturbation theory:•FLEX-approximation
nnUcctH effjiij
Results
TN
No SC phase
Ueff=0.5eV
Discussion
AF
SC Pressure
Tem
pera
t ure
’-(ET)2ICl2
Suppress(→1D)
2D
Pressure
Tem
pera
ture
AF
’-(ET)2AuCl2
Enhance(2D→3D)Suppress
(→1D)No SC phase
Fermi surface nesting?U?
a*
c*
b*
TN
intralayerdimensionality
tem
pera
ture
TN
TSC
interlayer
dimensionality
Discussion (2)
TN
PressureAuCl2
PressureICl2
Fermi surfaces (extended zone)
12GPa 20GPa
Summary
’-(ET)2AuCl2
AF phase is stabilized under applied pressures.
Reason:Higher-dimensionalityU → better FS nesting
Fermi surfaces (2D, b-axis-off)
0GPa 4GPa 8Gpa
12GPa 16GPa 20GPa
a*
c*
→Destabilize AF?
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