Phase Dependent Thermopower in Andreev Interferometers

We report measurements of the thermopower S of mesoscopic Andreev interferometers, which are hybrid loops with one arm fabricated from a superconductor (Al), and one arm from a normal metal (Au). S depends on the phase of electrons in the interferometer, oscillating as a function of magnetic flux with a period of one flux quantum Φ₀0ex0ex=0ex0exh/2e. The magnitude of S increases as the temperature T is lowered, reaching a maximum at T~0.14 K, and decreases at lower temperatures. The symmetry of S oscillations with respect to magnetic flux depends on the topology of the sample.