Nonlocal Andreev reflection, fractional charge and current-phase   relation in topological bilayer exciton condensate junctions
  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. 
M. Veldhorst, M. Hoek, M. Snelder, H. Hilgenkamp, A.A. Golubov, and A.   Brinkman
cond-mat.mes-hall cond-mat.str-el cond-mat.supr-con