Phase Diagram of $\beta'$-(BEDT-TTF)$_2$ICl$_2$ under High Pressure Based on the First-Principles Electronic Structure

TL;DR

This paper investigates the pressure-induced superconductivity in $eta'$-(BEDT-TTF)$_2$ICl$_2$, revealing a phase diagram where $d_{xy}$-wave superconductivity emerges near antiferromagnetism due to dimensional crossover.

Contribution

It provides a first-principles based theoretical phase diagram explaining the high-pressure superconductivity in an organic material.

Findings

Superconductivity with $d_{xy}$-like symmetry is found near the antiferromagnetic phase.

Pressure induces a crossover from one-dimensional to two-dimensional electronic behavior.

The highest $T_c$ among organic superconductors is explained by the model.

Abstract

We present a theoretical study on the superconductivity of $\beta'$-(BEDT-TTF)$_2$ICl$_2$ at $T_{\rm c}=$14.2 K under a high hydrostatic pressure recently found, which is the highest among organic superconductors. In the present work, we study an effective model using the fluctuation-exchange (FLEX) approximation based on the results of first-principles calculation. In the obtained phase diagram, the superconductivity with $d_{xy}$-like symmetry is realized next to the antiferromagnetic phase, as a result of the one-dimensional to two-dimensional crossover driven by the pressure.