Phase Diagram and Pairing Symmetry of the Two-Dimensional t-J Model by a Variation Theory

TL;DR

This study uses variational Monte Carlo methods to explore the phase diagram and pairing symmetries of the two-dimensional t-J model, revealing the dominance of d_{x^2-y^2} pairing near half filling and extended s-wave at low densities.

Contribution

It provides a comprehensive analysis of pairing symmetries and phase stability in the 2D t-J model using Gutzwiller-Jastrow wave functions, including the impact of a three-site term.

Findings

d_{x^2-y^2} wave pairing is most stable near half filling

Extended s-wave becomes favorable at low electron densities for large J/t

Gutzwiller wave function is exact in the low-density supersymmetric case

Abstract

Two-dimensional t-J model is studied by a variational Monte Carlo method, using Gutzwiller-Jastrow-type wave functions. Various kinds of superconducting pairing symmetries are compared in order to determine the phase diagram of the ground state in the full J/t-n plane. Near the half filling where the high temperature superconductivity is expected, the d_{x^2-y^2} wave pairing state is always the most stable among various symmetries. The three-site term hardly changes the phase diagram in this regime. In the low electron density, the extended s-type wave becomes a quantitatively good state for large J/t, although the energy gain is small. The Gutzwiller wave function is shown to be the exact ground state in the low-electron-density limit for the supersymmetric case (J/t=2).