Coherent thermoelectric effects in mesoscopic Andreev interferometers

We investigate thermoelectric transport through quantum chaotic, ballistic mesoscopic Andreev interferometers. We show that the ratio of the thermal and the charge conductances exhibits large oscillations with the phase difference phi between the two superconducting contacts, and that the Wiedemann-Franz law holds only when phi = pi. A rather large average thermopower emerges whenever there is an asymmetry in the dwell times to reach the superconducting contacts. When this is the case, the thermopower is odd in phi. In contrast, when the average times to reach either superconducting contact are the same, the average thermopower is zero, in agreement with earlier works on diffusive Andreev interferometers. We show however that mesoscopic effects (analogous to universal conductance fluctuations) lead to a sample-dependent thermopower which is systematically even in phi. Copyright (C) EPLA, 2010