Variational Monte Carlo studies of a t-J model on an anisotropic triangular lattice

TL;DR

This study uses variational Monte Carlo methods to analyze a t-J model on an anisotropic triangular lattice, exploring the stability of superconducting and antiferromagnetic states as the lattice anisotropy varies.

Contribution

It provides new insights into the phase stability of superconducting and magnetic states in an anisotropic triangular lattice t-J model, relevant to organic superconductors.

Findings

Superconducting state switches from d+id to d wave as t'/t decreases.

Antiferromagnetic state stabilizes for t'/t 0.7 at half filling.

Phase separation and Nagaoka ferromagnetism are also observed.

Abstract

With the insulating phase of \kappa-(BEDT-TTF)_2X in mind, we study a t-J model on an anisotropic triangular lattice, where the hopping integral is t' in one of the three directions, using a variational Monte Carlo method. By changing the value of t'/t, we study the stability of superconducting (SC) states with d- and d+id-wave symmetries and of an antiferromagnetic (AF) state. As t'/t decreases from 1, the stable state immediately switches from the d+id wave to the d wave. The AF state is stabilized from the normal spin liquid state for t'/t\lsim 0.7 at half filling. We also take account of Nagaoka ferromagnetism and a phase separation.