Exact solution and magnetic properties of an anisotropic spin ladder

TL;DR

This paper provides an exact analytical solution for an anisotropic spin ladder model, analyzing its magnetic properties and quantum phase transitions using Bethe ansatz techniques.

Contribution

It introduces an exact solution for an integrable anisotropic spin ladder with XYZ-type rung interactions, detailing its magnetic behavior and phase transitions.

Findings

Identification of gap opening conditions depending on anisotropic couplings

Analytic expressions for critical fields of quantum phase transitions

Observation of directional magnetization and susceptibility effects

Abstract

We study an integrable two-leg spin-1/2 ladder with an XYZ-type rung interaction. Exact rung states and rung energies are obtained for the anisotropic rung coupling in the presence of a magnetic field. Magnetic properties are analyzed at both zero and finite temperatures via the thermodynamic Bethe ansatz and the high-temperature expansion. According to different couplings in the anisotropic rung interaction, there are two cases in which a gap opens, with the ground state involving one or two components in the absence of a magnetic field. We obtain the analytic expressions of all critical fields for the field-induced quantum phase transitions (QPT). Anisotropic rung interaction leads to such effects as separated magnetizations and susceptibilities in different directions, lowered inflection points and remnant weak variation of the magnetization after the last QPT.