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

M. Veldhorst; M. Hoek; M. Snelder; H. Hilgenkamp; A. A. Golubov; A. Brinkman

doi:10.1103/PhysRevB.90.035428

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

M. Veldhorst, M. Hoek, M. Snelder, H. Hilgenkamp, A. A. Golubov, A. Brinkman

DOI 10.1103/PhysRevB.90.035428 · Physical Review B

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Abstract

We study Andreev reflection and Josephson currents in topological bilayer exciton condensates (TECs). 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–topological-insulator–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.