Quantum order by disorder in a semiclassical spin ice

TL;DR

This paper investigates how quantum fluctuations lift degeneracy in a semiclassical spin ice model, leading to a specific ordered state via the quantum order by disorder mechanism, with implications for understanding frustrated magnetic systems.

Contribution

It demonstrates the quantum order by disorder phenomenon in a S>1 Heisenberg model with strong anisotropy on a pyrochlore lattice, revealing the selection of a q=0 ordered state.

Findings

Quantum fluctuations lift ground state degeneracy.

A first-order phase transition to ordered state occurs.

The ordered state is selected via quantum order by disorder.

Abstract

We study the S>1 nearest-neighbor Heisenberg model with a ferromagnetic interaction J and a large non-collinear <111> easy-axis anisotropy D on a pyrochlore lattice. For a finite D>>|J|, the low-energy physics is described by a < 111 > Ising model with second- and third-neighbor exchange interactions. The extensive degeneracy of the ground state manifold in the infinite anisotropic limit is lifted by the transverse quantum fluctuations, and a q=0 ordered state is selected via the quantum order by disorder machanism, through a first-order phase transition at low temperature.