Coulomb enhancement of superconducting pair-pair correlations in a 3 4 -filled model for κ − ( BEDT-TTF ) 2 X
AffiliationUniv Arizona, Dept Phys
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PublisherAMER PHYSICAL SOC
CitationCoulomb enhancement of superconducting pair-pair correlations in a 3 4 -filled model for κ − ( BEDT-TTF ) 2 X 2016, 93 (20) Physical Review B
JournalPhysical Review B
Rights©2016 American Physical Society.
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AbstractWe present the results of precise correlated-electron calculations on the monomer lattices of the organic charge-transfer solids kappa-(BEDT-TTF)(2)X for 32 and 64 molecular sites. Our calculations are for band parameters corresponding to X = Cu[N(CN)(2)]Cl and Cu-2(CN)(3), which are semiconducting antiferromagnetic and quantum spin liquid, respectively, at ambient pressure. We have performed our calculations for variable electron densities. per BEDT-TTF molecule, with. ranging from 1 to 2. We find that d-wave superconducting pair-pair correlations are enhanced by electron-electron interactions only for a narrow carrier concentration about rho = 1.5, which is precisely the carrier concentration where superconductivity in the charge-transfer solids occurs. Our results indicate that the enhancement in pair-pair correlations is not related to antiferromagnetic order, but to a proximate hidden spin-singlet state that manifests itself as a charge-ordered state in other charge-transfer solids. Long-range superconducting order does not appear to be present in the purely electronic model, suggesting that electronphonon interactions also must play a role in a complete theory of superconductivity.
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