Quantitative measurements of the thermopower of Andreev interferometers

Using a new second-derivative technique and local thermometers in a mesoscopic metallic sample, we have obtained for the first time quantitative measurements of the low-field and temperature-dependent thermopower of Andreev interferometers. These Andreev interferometers are shorter in length and of a different topology than those measured by Eom et al. The thermopower is found to be an antisymmetric periodic function of the field. The temperature dependence of the thermopower is nonmonotonic, with a minimum at a temperature of ≃ 0.5 K, and the measured amplitude is much smaller than that estimated previously. These results are discussed from the perspective of Andreev reflection at the normal-metal/superconductor interface.