Finite-momentum condensate of magnetic excitons in a bilayer quantum Hall system

TL;DR

This paper investigates a phase transition in a bilayer quantum Hall system, showing that a finite-momentum condensate of magnetic excitons emerges at small interlayer separations, replacing the zero-momentum condensate.

Contribution

It introduces a bosonization approach to analyze magnetic exciton condensates and identifies a first-order phase transition to a finite-momentum condensate.

Findings

Finite-momentum condensate exists at small interlayer distances.

A first-order phase transition from Halperin 111 state to finite-momentum condensate.

Evidence of a gapped excitation spectrum in the finite-momentum phase.

Abstract

We study the bilayer quantum Hall system at total filling factor \nu_T = 1 within a bosonization formalism which allows us to approximately treat the magnetic exciton as a boson. We show that in the region where the distance between the two layers is comparable to the magnetic length, the ground state of the system can be seen as a finite-momentum condensate of magnetic excitons provided that the excitation spectrum is gapped. We analyze the stability of such a phase within the Bogoliubov approximation firstly assuming that only one momentum Q0 is macroscopically occupied and later we consider the same situation for two modes \pm Q0. We find strong evidences that a first-order quantum phase transition at small interlayer separation takes place from a zero-momentum condensate phase, which corresponds to Halperin 111 state, to a finite-momentum condensate of magnetic excitons.