Thermopower oscillations in mesoscopic Andreev interferometers

Anomalously large thermopower of mesoscopic normal-metal/superconductor interferometers has been investigated by Chandrasekhar et al. It was shown that, depending on the geometry of the interferometer, the thermopower is either symmetric or antisymmetric periodic function of the magnetic flux. We develop a detailed theory of the observed thermoelectric phenomena in the framework of the nonequilibrium quasiclassical approach. In particular, we provide a possible explanation of the symmetric thermopower oscillations. This effect is attributed to the electron-hole symmetry violation that originates in the steady-state charge imbalance between different arms of the interferometer. Our theory can be tested by an additional control over the charge imbalance in a modified setup geometry. We also predict a sign reversal behavior of the thermopower with increasing temperature that is consistent with the experiments by Parsons et al.