2d frustrated Ising model with four phases

TL;DR

This paper investigates a 2D disordered Ising model with anisotropic bonds, revealing four distinct phases and multiple phase transitions through an approximate analytical approach.

Contribution

It introduces a novel approximate method to analyze a 2D disordered Ising system with anisotropic and correlated disorder, uncovering four phases and multiple phase transitions.

Findings

Identifies four different phases: antiferromagnetic, glassy-like, ferromagnetic, paramagnetic.

Discovers three second-order phase transitions between these phases.

Shows that anisotropic and correlated disorder lead to complex phase behavior.

Abstract

In this paper we consider a 2d random Ising system on a square lattice with nearest neighbour interactions. The disorder is short range correlated and asymmetry between the vertical and the horizontal direction is admitted. More precisely, the vertical bonds are supposed to be non random while the horizontal bonds alternate: one row of all non random horizontal bonds is followed by one row where they are independent dichotomic random variables. We solve the model using an approximate approach that replace the quenched average with an annealed average under the constraint that the number of frustrated plaquettes is keep fixed and equals that of the true system. The surprising fact is that for some choices of the parameters of the model there are three second order phase transitions separating four different phases: antiferromagnetic, glassy-like, ferromagnetic and paramagnetic.