Confinement-deconfinement transition due to spontaneous symmetry breaking in quantum Hall bilayers

TL;DR

This paper explores how magnetic fields and gate voltages induce a confinement-deconfinement transition in quantum Hall bilayers with helical exciton condensates, revealing new edge state behaviors and potential insights into quark confinement.

Contribution

It demonstrates the existence of a confinement-deconfinement transition in quantum Hall bilayers with helical exciton condensates, controlled by external parameters, and discusses its implications for low-energy excitations.

Findings

Charged edge excitations are confined in narrow Hall bars.

Magnetic field and gate voltages control the confinement-deconfinement transition.

Nonlocal conductance can probe the transition.

Abstract

Band-inverted electron-hole bilayers support quantum spin Hall insulator and exciton condensate phases. We investigate such a bilayer in an external magnetic field. We show that the interlayer correlations lead to formation of a helical quantum Hall exciton condensate state. In contrast to the chiral edge states of the quantum Hall exciton condensate in electron-electron bilayers, existence of the counterpropagating edge modes results in formation of a ground state spin-texture not supporting gapless single-particle excitations. This feature has deep consequences for the low energy behavior of the system. Namely, the charged edge excitations in a sufficiently narrow Hall bar are confined, i.e.~a charge on one of the edges always gives rise to an opposite charge on the other edge. Moreover, we show that magnetic field and gate voltages allow to control confinement-deconfinement transition of charged edge excitations, which can be probed with nonlocal conductance. Confinement-deconfinement transitions are of great interest, not least because of their possible significance in shedding light on the confinement problem of quarks.