The quantum compass chain in a transverse magnetic field

TL;DR

This paper investigates the magnetic phase transitions of a spin-1/2 quantum compass chain under a transverse magnetic field, revealing multiple quantum phase transitions and the nature of the intermediate spin-flop phase.

Contribution

It provides an analytical and numerical analysis of the quantum compass chain's phase diagram in a transverse field, identifying critical fields and phase transition types.

Findings

Identification of four gapped regions in zero field

Field-induced Ising-type phase transitions in two regions

Discovery of two quantum phase transitions in the ground state

Abstract

We study the magnetic behaviors of a spin-1/2 quantum compass chain (QCC) in a transverse magnetic field, by means of the analytical spinless fermion approach and numerical Lanczos method. In the absence of the magnetic field, the phase diagram is divided into four gapped regions. To determine what happens by applying a transverse magnetic field, using the spinless fermion approach, critical fields are obtained as a function of exchanges. Our analytical results show, the field-induced effects depend on in which one of the four regions the system is. In two regions of the phase diagram, the Ising-type phase transition happens in a finite field. In another region, we have identified two quantum phase transitions in the ground state magnetic phase diagram. These quantum phase transitions belong to the universality class of the commensurate-incommensurate phase transition. We also present a detailed numerical analysis of the low energy spectrum and the ground state magnetic phase diagram. In particular, we show that the intermediate state ($h_{c_{1}}<h<h_{c_{2}}$) is gapful, describing the spin-flop phase.