Spin-Wave Analysis of the Antiferromagnetic Plane Rotator Model on the Triangular Lattice —Symmetry Breaking in a Magnetic Field

Abstract

Lowest-order spin-wave analysis is applied to the antiferromagnetic plane rotator model on the triangular lattice in order to study the low-temperature properties in the presence of magnetic fields. Equilibrium spin configuration in the zero-temperature limit is calculated as a function of the magnetic field. It is found that the thermal-fluctuation effect reduces a continuous degeneracy of the ground state to a discrete one at non-zero temperatures.