Multicriticality and entanglement in the one-dimensional quantum compass model

TL;DR

This paper investigates the 1D quantum compass model, revealing a multicritical point where different phase transition lines intersect, and analyzes entanglement measures to distinguish between types of phase transitions.

Contribution

It provides an exact mapping to the quantum Ising model, uncovering hidden features of the phase transition and analyzing entanglement in different phases.

Findings

Multicritical point where first- and second-order transitions intersect

Entanglement measures signal second-order but not first-order transitions

Exact mapping to quantum Ising model reveals hidden phase transition features

Abstract

We study the one-dimensional (1D) quantum compass model with two independent parameters by means of an exact mapping to the quantum Ising model. This allows us to uncover hidden features of the quantum phase transition in the ordinary one-parameter quantum compass model, showing that it occurs at a multicritical point where a line of first-order transitions intersects a line of second-order symmetry-breaking transitions of Ising type. We calculate the concurrence and the block entanglement entropy in the four ground state phases, and find that these entanglement measures accurately signal the second-order, but not the first-order, transitions.