Nature of the Quantum Phase Transition in Quantum Compass Model

TL;DR

This paper investigates the quantum phase transition in the quantum compass model, revealing it to be a first-order transition through a mean-field approach that accounts for key fluctuations.

Contribution

It introduces a fermionic mapping of the quantum compass model and demonstrates the robustness of the first-order transition result with fluctuation corrections.

Findings

Quantum phase transition at Jx=Jz is first order.

Mean-field approximation effectively captures key fluctuations.

Transition point remains robust under second-order fluctuations.

Abstract

In this work, we show that the quantum compass model on an square lattice can be mapped to a fermionic model with local density interaction. We introduce a mean-field approximation where the most important fluctuations, those perpendicular to the ordering direction, are taken into account exactly. It is found that the quantum phase transition point at $J_x=J_z$ marks a first order phase transition. We also show that the mean field result is robust against the remaining fluctuation corrections up to the second order.