Commensurate and incommensurate ground states of Cs_2CuCl_4 in a magnetic field

TL;DR

This paper investigates the magnetic ground states of Cs_2CuCl_4 under different magnetic field orientations, revealing a transition between incommensurate and commensurate phases, aligning with experimental observations.

Contribution

It introduces a controlled Bose gas mapping approach to analyze the ground states of Cs_2CuCl_4 in magnetic fields, highlighting field-dependent phase transitions.

Findings

Zero-temperature transition between incommensurate and commensurate phases in longitudinal field.

Only incommensurate order observed in transverse field.

Results agree with experimental data.

Abstract

We present calculations of the magnetic ground state of Cs_2CuCl_4 in an applied magnetic field, with the aim of understanding the commensurately ordered state that has been discovered in recent experiments. This layered material is a realization of a Heisenberg antiferromagnet on an anisotropic triangular lattice. Its behavior in a magnetic field depends on field orientation, because of weak Dzyaloshinskii-Moriya interactions.We study the system by mapping the spin-1/2 Heisenberg Hamiltonian onto a Bose gas with hard core repulsion. This Bose gas is dilute, and calculations are controlled, close to the saturation field. We find a zero-temperature transition between incommensurate and commensurate phases as longitudinal field strength is varied, but only incommensurate order in a transverse field. Results for both field orientations are consistent with experiment.