Splitting the multiphase point

TL;DR

This paper investigates how different perturbations such as quantum fluctuations, thermal fluctuations, and spin softening influence the degeneracy and phase structure at multiphase points in models with competing interactions like the ANNNI model.

Contribution

It compares the effects of three types of perturbations on lifting degeneracy and generating long-period phases at multiphase points in such models.

Findings

Quantum fluctuations can lift degeneracy differently than thermal fluctuations.

Softening of spins influences the stability of long-period phases.

Perturbations lead to the emergence of complex phase sequences.

Abstract

Models with competing interactions, for example the ANNNI model, can have special points at which the ground state is infinitely degenerate, so-called multiphase points. Small perturbations can lift this degeneracy and give rise to infinite sequences of long-period phases. This paper compares the effect of three possible perturbations, quantum fluctuations, thermal fluctuations and the softening of the spins from their quantised positions.