Quantum Ferromagnetism and Phase Transitions in Double-Layer Quantum Hall Systems

TL;DR

This paper investigates quantum ferromagnetism and phase transitions in double-layer quantum Hall systems, revealing how interlayer correlations lead to complex magnetic and phase behaviors, including a collective commensurate-incommensurate transition.

Contribution

It demonstrates the occurrence of quantum ferromagnetism and detailed phase transition phenomena in double-layer quantum Hall systems, highlighting the effects of magnetic fields on magnetic order.

Findings

Interlayer correlations induce ferromagnetic behavior.

Parallel magnetic fields cause a commensurate-incommensurate phase transition.

Rich variety of quantum and finite temperature phase transitions.

Abstract

Double layer quantum Hall systems have interesting properties associated with interlayer correlations. At $\nu =1/m$ where $m$ is an odd integer they exhibit spontaneous symmetry breaking equivalent to that of spin $1/2$ easy-plane ferromagnets, with the layer degree of freedom playing the role of spin. We explore the rich variety of quantum and finite temperature phase transitions in these systems. In particular, we show that a magnetic field oriented parallel to the layers induces a highly collective commensurate-incommensurate phase transition in the magnetic order.