Designing exciton-condensate Josephson junction in quantum Hall heterostructures

The exciton condensate (EC), a coherent state of electron-hole pairs, has been robustly realized in two-dimensional quantum Hall bilayer systems at integer fillings. However, direct experimental evidence for many of the remarkable signatures of phase coherence, such as an in-plane Josephson effect, has been lacking. In this work, we propose a gate-defined exciton-condensate Josephson junction suitable for demonstrating the Josephson effect in vdW heterostructures. The design is similar to the S-I-S superconducting Josephson junction but functions with a completely different microscopic mechanism: two exciton condensates are spatially separated by a gated region that is nearly layer-polarized, and the variation of layer pseudospin mediates a Josephson coupling sufficiently strong to have an observable effect. The Josephson coupling can be controlled by both the gate voltage and the magnetic field, and we show our design's high range of tunability and experimental feasibility with realistic parameters in vdW heterostructures.