The Dimer Model for k-phase Organic Superconductors

TL;DR

This paper models the electronic structure of k-phase BEDT-TTF salts using a simplified tight-binding approach derived from ab-initio calculations, leading to insights into their superconducting pairing symmetry and properties.

Contribution

It introduces a minimal tight-binding model for k-phase BEDT-TTF salts based on ab-initio data, enabling analysis of their superconducting behavior.

Findings

The model accurately reproduces the electronic band structure.

Superconductivity is consistent with isotropic s-wave pairing.

Residual interactions may explain diverse physical properties.

Abstract

We prove that the upper electronic bands of k-phase BEDT-TTF salts are adequately modeled by an half-filled tight-binding lattice with one site per cell. The band parameters are derived from recent ab-initio calculations, getting a very simple but extremely accurate one-electron picture. This picture allows us to solve the BCS gap equation adopting a real-space pairing potential. Comparison of the calculated superconducting properties with the experimental data points to isotropic s_0-pairing. Residual many-body or phonon-mediated interactions offer a plausible explanation of the large variety of physical properties observed in k-phase BEDT-TTF salts.