Nonlocal Andreev reflection, fractional charge and current-phase relation in topological bilayer exciton condensate junctions

TL;DR

This paper investigates topological bilayer exciton condensates, revealing perfect nonlocal Andreev reflection, tunable reflection regimes, and signatures of fractional charge through unique current-phase relationships and bound state properties.

Contribution

It introduces the study of nonlocal Andreev reflection and fractional charge signatures in topological bilayer exciton condensate junctions, highlighting their unique transport and bound state characteristics.

Findings

Perfect nonlocal Andreev reflection enables spin-entangled currents.

Tunable reflection regimes from retro to specular.

Signatures of fractional charge in current-phase relations.

Abstract

We study Andreev reflection and Josephson currents in topological bilayer exciton condensates (TEC). These systems can create 100% spin entangled nonlocal currents with high amplitudes due to perfect nonlocal Andreev reflection. This Andreev reflection process can be gate tuned from a regime of purely retro reflection to purely specular reflection. We have studied the bound states in TEC-TI-TEC Josephson junctions and find a gapless dispersion for perpendicular incidence. The presence of a sharp transition in the supercurrent-phase relationship when the system is in equilibrium is a signature of fractional charge, which can be further revealed in ac measurements faster than relaxation processes via Landau-Zener processes.