Order in a Spatially Anisotropic Triangular Antiferromagnet

TL;DR

This paper investigates the phase diagram of a spin-1/2 Heisenberg antiferromagnet on an anisotropic triangular lattice, revealing conditions under which spiral or collinear antiferromagnetic orders are stable, with implications for understanding Cs2CuCl4.

Contribution

The study applies a renormalization group analysis including marginal couplings to clarify the stability of magnetic orders in an anisotropic triangular antiferromagnet.

Findings

Spiral order is stable over most of the phase diagram with Dzyaloshinskii-Moriya interaction.

Collinear antiferromagnetic order can survive at very weak interchain and DM couplings.

Cs2CuCl4 is in the spiral order stable region of the phase diagram.

Abstract

The phase diagram of the spin-1/2 Heisenberg antiferromagnet on an anisotropic triangular lattice of weakly coupled chains, a model relevant to Cs2CuCl4, is investigated using a renormalization group analysis, which includes marginal couplings important for connecting to numerical studies of this model. In particular, the relative stability of incommensurate spiral spin-density order and collinear antiferromagnetic order is studied. While incommensurate spiral order is found to exist over most of the phase diagram in the presence of a Dzyaloshinskii-Moriya (DM) interaction, at small interchain and extremely weak DM couplings, collinear antiferromagnetic order can survive. Our results imply that Cs2CuCl4 is well within the part of the phase diagram where spiral order is stable. The implications of the renormalization group analysis for numerical studies, many of which have found spin-liquidlike behavior, are discussed.