Origin of the Superconductivity in \beta'-(BEDT-TTF)_2ICl_2 under High Pressure and \beta-(BEDT-TTF)_2X at Ambient Pressure

TL;DR

This paper uses a theoretical model to explain the high-pressure-induced superconductivity in eta'-(BEDT-TTF)_2ICl_2, revealing a d-wave pairing mechanism and a maximum Tc of 16-18K, consistent with experimental observations.

Contribution

It demonstrates that the anisotropic triangular lattice Hubbard model explains the superconductivity and phase diagram of eta'-(BEDT-TTF)_2ICl_2 under pressure, highlighting the dimensional crossover effect.

Findings

Superconductivity with d_{x^2-y^2} symmetry appears near the antiferromagnetic phase.

Maximum Tc estimated at 16-18K under high pressure.

The same framework explains superconductivity in eta-(BEDT-TTF)_2X at ambient pressure.

Abstract

We present a theoretical study on the superconductivity in \beta'-(BEDT-TTF)_2ICl_2 at Tc=14.2K under high hydrostatic pressure found by Taniguchi et al., which is the highest record among organic superconductors. Its electronic structure is well expressed by the anisotropic triangular lattice Hubbard model at half filling. In the present work, we study this effective model by using the fluctuation-exchange (FLEX) approximation. In the obtained phase diagram, the superconductivity with d_{x^2-y^2} like symmetry is realized next to the antiferromagnetic (AF) insulating phase, as a result of the 1D-2D dimensional crossover driven by the pressure. The obtained maximum Tc is 16-18K. In addition, the superconductivity in \beta-(BEDT-TTF)_2X is also understood in the same framework.