Quasi-excitations and superconductivity in the t-J model on a ladder

TL;DR

This paper investigates the t-J ladder model using a slave-fermion-CP^1 formalism, revealing how gauge dynamics influence quasi-excitations and demonstrating that superconductivity with d-wave symmetry emerges from short-range antiferromagnetism.

Contribution

It introduces a low-energy effective field theory for the t-J ladder model, highlighting the role of topological terms and gauge dynamics in quasi-excitation properties and superconductivity.

Findings

Gauge dynamics depend on the number of ladder legs.

Superconductivity with d-wave symmetry emerges from antiferromagnetic correlations.

Topological terms influence quasi-excitation behavior.

Abstract

We study the t-J model on a ladder by using slave-fermion-CP^1 formalism which is quite useful for study of lightly-doped high-T_c cuprates. By integrating half of spin variables, we obtain a low-energy effective field theory whose spin part is nothing but CP^1 sigma model. We especially focus on dynamics of composite gauge field which determines properties of quasi-excitations. Value of the coefficient of the topological term strongly influences gauge dynamics and explaines why properties of quasi-excitations depend on the number of legs of ladder. We also show that superconductivity appears as a result of short-range antiferromagnetism and order parameter has d-wave type symmetry.