Thermopower of Metals in High Magnetic-Fields

The thermopower of polycrystalline copper, silver, gold, aluminum, indium and lead was measured from liquid helium temperature to 100 K in magnetic fields up to 50 kG. Large enhancement of thermopower by the magnetic field was found, and a peak in the temperature dependence of delta S(H,T) was observed for the first time. The field results in a large enhancement of the phonon-drag thermopower in contrast to early expectation of MacDonald and Pearson. Two theoretical models were developed to explain the observed effects. The electron-diffusion model relies on the well-known Mott formula for the diffusion-thermopower, and Wiedemann-Franz law. The phonon-drag model is based on the semiclassical electron dynamics in a magnetic field, and also a concept from Pippard. It is found that these two models together can give a good explanation of the experimental results.