Antiferromagnetism and Superconductivity in layered organic conductors: Variational cluster approach

TL;DR

This study uses variational cluster perturbation theory to explore antiferromagnetism and superconductivity in layered organic conductors, revealing phase transitions driven by interaction strength and hopping parameters.

Contribution

It applies the V-CPT method to the dimer model of layered organic conductors, identifying phase boundaries between antiferromagnetic and superconducting states.

Findings

Antiferromagnetism exists for large U and low t'

d-wave superconductivity appears as U decreases

Phase diagram includes AF, dSC, and Mott disordered phases

Abstract

The $\kappa$-(ET)$_2$X layered conductors (where ET stands for BEDT-TTF) are studied within the dimer model as a function of the diagonal hopping $t^\prime$ and Hubbard repulsion $U$. Antiferromagnetism and d-wave superconductivity are investigated at zero temperature using variational cluster perturbation theory (V-CPT). For large $U$, N\'eel antiferromagnetism exists for $t' < t'_{c2}$, with $t'_{c2}\sim 0.9$. For fixed $t'$, as $U$ is decreased (or pressure increased), a $d_{x^2-y^2}$ superconducting phase appears. When $U$ is decreased further, the a $d_{xy}$ order takes over. There is a critical value of $t'_{c1}\sim 0.8$ of $t'$ beyond which the AF and dSC phases are separated by Mott disordered phase.