Quantum transport simulation of exciton condensate transport physics in a double layer graphene system

TL;DR

This paper presents a quantum transport simulation of exciton condensate physics in a double layer graphene system, revealing key phenomena like Coulomb drag, critical currents, and non-local effects relevant for pseudospintronic devices.

Contribution

It introduces a novel quantum transport simulator incorporating non-local Fock exchange interactions to model exciton condensate transport in bilayer graphene.

Findings

Finite size effects influence transport properties.

Identification of Coulomb drag-counterflow currents.

Observation of an Andreev-like reflection process.

Abstract

Spatially indirect electron-hole exciton condensates stabilized by interlayer Fock exchange interactions have been predicted in systems containing a pair of two-dimensional semiconductor or semimetal layers separated by a thin tunnel dielectric. The layer degree of freedom in these systems can be described as a pseudospin. Condensation is then analogous to ferromagnetism, and the interplay between collective and quasiparticle contributions to transport is analogous to phenomena that are heavily studied in spintronics. These phenomena are the basis for pseudospintronic device proposals based on possible low-voltage switching between high (nearly shorted) and low interlayer conductance states and on near perfect Coulomb drag-counterflow current along the layers. In this work, a quantum transport simulator incorporating a non-local Fock exchange interaction is presented, and used to model the essential transport physics in the bilayer graphene system. Finite size effects, Coulomb drag-counterflow current, critical interlayer currents beyond which interlayer DC conductance collapses at sub-thermal voltages, non-local coupling between interlayer critical currents in multiple lead devices, and an Andreev-like reflection process are illustrated.