The anisotropic Heisenberg chain in coexisting transverse and longitudinal magnetic fields

TL;DR

This paper investigates the phase transitions and ground state properties of the one-dimensional spin-1/2 XXZ model under mixed magnetic fields, combining mean-field and conformal field theory methods, with relevance to experimental materials.

Contribution

It introduces a new combined theoretical approach to analyze the XXZ model in mixed fields and maps its phase diagram, extending understanding of magnetic phase transitions in quasi-one-dimensional systems.

Findings

Identified the ground state phase diagram under mixed magnetic fields.

Analyzed the model's behavior in low transverse fields using conformal field theory.

Discussed relevance to phase transitions observed in Cs2CoCl4.

Abstract

The one-dimensional spin-1/2 $XXZ$ model in a mixed transverse and longitudinal magnetic field is studied. Using the specially developed version of the mean-field approximation the order-disorder transition induced by the magnetic field is investigated. The ground state phase diagram is obtained. The behavior of the model in low transverse field is studied on the base of conformal field theory. The relevance of our results to the observed phase transition in the quasi-one-dimensional antiferromagnet $Cs_2 Co Cl_4$ is discussed.