Critical Dimerization Strength of the Quarter-Filled t-J Model

TL;DR

This study uses exact diagonalization to analyze the ground state of a quarter-filled dimerized t-J model, revealing how competing dimerization effects induce an insulator-superconductor transition and mapping the phase diagram.

Contribution

It provides the first detailed phase diagram of the quarter-filled dimerized t-J model considering both hopping and exchange dimerizations.

Findings

Competition between dimerization types drives insulator-superconductor transition

Charge and spin correlations vary with dimerization strength

Phase diagram maps transition boundaries

Abstract

An exact-diagonalization technique on small clusters is used to study the ground state of the dimerized t-J model at quarter filling. The equal-time charge and spin correlations, charge and spin gaps, and binding energy are calculated for the two-dimensional lattice with a spatial dimerization pattern corresponding to organic conductors $\kappa-(BEDT-TTF)_2X$. We show that competition between the effects of two types of dimerization, i.e., dimerization in the hopping integral and dimerization in the exchange interaction, leads to the insulator-superconductor transition in the ground state of the model. The phase diagram is thereby presented.