  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.
