Study on nonmagnetic impurities in the superconducting state of two-dimensional t-J model

TL;DR

This study investigates how nonmagnetic impurities affect the superconducting state in the two-dimensional t-J model, revealing suppression of the order parameter, induced s-wave components, and local charge density oscillations.

Contribution

It introduces a numerical analysis of impurity effects on d-wave superconductivity in the t-J model using Bogoliubov de Gennes equations with slave-boson mean-field approximation.

Findings

Suppression of d_{x^2-y^2}-wave order near impurities

Induction of extended s-wave component due to spatial variation

Friedel oscillations cause local charge density wave features

Abstract

We study the effect of nonmagnetic impurities in the superconducting state of the t-J model. The Bogoliubov de Gennes equation is derived using a slave-boson mean-field approximation, and we solve it numerically at T=0. The d_{x^2-y^2}-wave order parameter is suppressed near an impurity and its spatial variation induces the extended s-wave component. We also find the local charge density wave (CDW)-like feature due to the Friedel oscillations. This leads to the splitting of the expected zero-energy Andreev bound state. Therefore the system is unlikely introducing a localized state of other symmetry such as superconductivity with broken time reversal symmetry or antiferromagnetism.