Lifting of Multiphase Degeneracy by Quantum Fluctuations

TL;DR

This paper investigates how quantum fluctuations influence the phase structure of a frustrated Heisenberg model with strong anisotropy, revealing that they lift degeneracy and stabilize a sequence of modulated phases, and induce layering transitions.

Contribution

It demonstrates that quantum fluctuations lift multiphase degeneracy and stabilize a sequence of modulated phases in a frustrated spin model, extending understanding beyond classical limits.

Findings

Degeneracy is lifted by quantum fluctuations.

Sequence of stable phases with wavelengths 4,6,8,... is stabilized.

Quantum fluctuations induce layering transitions.

Abstract

We study the effect of quantum fluctuations on the multiphase point of the Heisenberg model with first- and second-neighbor competing interactions and strong uniaxial spin anisotropy $D$. By studying the structure of perturbation theory we show that the multiphase degeneracy which exists for $S=\infty$ (i.e., for the ANNNI model) is lifted and that the effect of quantum fluctuations is to stabilize a sequence of phases of wavelength 4,6,8,...~. This sequence is probably an infinite one. We also show that quantum fluctuations can mediate an infinite sequence of layering transitions through which an interface can unbind from a wall.