Transport in Coherent Quantum Hall Bilayers

TL;DR

This paper explores two phenomenological models for low-current transport in bilayer quantum Hall systems with exciton condensates, analyzing their predictions for current-voltage behavior and drag phenomena.

Contribution

It introduces a Landauer-Buttiker based model for Andreev scattering and a simplified p-ology model to describe the crossover from weak to strong interlayer coupling.

Findings

Predicts current-voltage relationships for various contact geometries.

Describes the behavior of tunnel current exceeding its critical value.

Establishes the universal development of large longitudinal drags as the condensate weakens.

Abstract

We discuss two phenomenological descriptions of low-current transport in bilayer quantum Hall system with exciton condensates, one based on a Landauer-Buttiker description of Andreev scattering at contacts to coherent bilayers and one based on a simplified single-parameter {\em p-ology} description of the weak to strong interlayer coupling crossover. The Andreev scattering phenomenology in intended to apply when the condensate is well developed and is used to predict current-voltage relationships for a variety of two contact geometries. We also apply this formalism to circumstances in which the tunnel current exceeds its critical value and the condensate is time-dependent. The {\em p-ology} approach is used to establish the universal development of large longitudinal drags, even in homogenous coherent samples, as the condensate weakens and the Hall drag is reduced.