Magnetoquantum oscillations of thermoelectric power in multisublevel quantum wires

The electron-diffusion and phonon-drag thermoelectric power (TEP) is investigated in a quantum wire as a function of the temperature, perpendicular magnetic field, and the electron density in the regime, where the conductivity is limited by elastic scattering. The wire is narrow in the growth direction with only the ground sublevel populated but is wide in the other confinement direction providing several occupied sublevels at zero field. Magnetic field causes depopulation of these sublevels, yielding quantum oscillations of the TEP and the conductance. An anomalous, large positive electron-diffusion TEP is obtained when the Fermi level lies slightly above a sublevel other than the ground sublevel due to the van Hove singularity at the subband edge. In contrast to the power-law temperature (T) dependence in higher dimensions, the phonon-drag TEP is proportional to $\exp \left(-ħ{\omega }_{\mathrm{F}}{/k}_{B}T\right)$ at low temperatures, where $ħ{\omega }_{\mathrm{F}}$ is the threshold phonon energy with a wave number $q_{\mathrm{F}}$ corresponding to the minimum momentum transfer for back scattering.