Thermodynamics of the Up-Up-Down Phase of the S = 1/2 Triangular-Lattice Antiferromagnet Cs$_2$CuBr$_4$

TL;DR

This study investigates the quantum stabilization of the up-up-down magnetic phase in Cs2CuBr4, revealing the significant role of quantum fluctuations and Dzyaloshinskii-Moriya interactions in its thermodynamic properties.

Contribution

It provides the first thermodynamic analysis of the quantum-stabilized up-up-down phase in a frustrated triangular-lattice antiferromagnet.

Findings

Quantum fluctuations stabilize the phase, not thermal fluctuations.

Magnon gaps are larger than in classical models, indicating quantum effects.

Presence of Dzyaloshinskii-Moriya interaction influences magnon gaps.

Abstract

Specific heat and the magnetocaloric effect are used to probe the field-induced up-up-down phase of Cs2CuBr4, a quasi-two-dimensional spin-1/2 triangular antiferromagnet with near-maximal frustration. The shape of the magnetic phase diagram shows that the phase is stabilized by quantum fluctuations, not by thermal fluctuations as in the corresponding phase of classical spins. The magnon gaps determined from the specific heat are considerably larger than those expected for a Heisenberg antiferromagnet, probably due to the presence of a small Dzyaloshinskii-Moriya interaction.