Reentrance of disorder in the anisotropic shuriken Ising model

TL;DR

This paper investigates reentrant disorder in a frustrated anisotropic shuriken Ising model, revealing a temperature-dependent transition between disordered phases driven by lattice anisotropy.

Contribution

It introduces the concept of reentrant disorder in magnetic systems and demonstrates it in the anisotropic shuriken lattice through combined numerical and analytical methods.

Findings

Disorder persists down to zero temperature in certain anisotropy regimes.

The phase diagram features a double crossover with less correlated regimes.

Complex diffuse scattering patterns are observed in the static structure factor.

Abstract

For a material to order upon cooling is common sense. What is more seldom is for disorder to reappear at lower temperature, which is known as reentrant behavior. Such resurgence of disorder has been observed in a variety of systems, ranging from Rochelle salts to nematic phases in liquid crystals. Frustration is often a key ingredient for reentrance mechanisms. Here we shall study a frustrated model, namely the anisotropic shuriken lattice, which offers a natural setting to explore an extension of the notion of reentrance between magnetic disordered phases. By tuning the anisotropy of the lattice, we open a window in the phase diagram where magnetic disorder prevails down to zero temperature. In this region, the competition between multiple disordered ground states gives rise to a double crossover where both the low- and high-temperature regimes are less correlated than the intervening classical spin liquid. This reentrance of disorder is characterized by an entropy plateau, a multi-step Curie law crossover and a rather complex diffuse scattering in the static structure factor. Those results are confirmed by complementary numerical and analytical methods: Monte Carlo simulations, Husimi-tree calculations and an exact decoration-iteration transformation.