Effect of electronic disorder on phonon-drag thermopower

Abstract

Using the quantum-transport equation and Keldysh diagrammatic technique, we investigate the phonon-drag thermopower in a disordered conductor. We consider phonon drag of three-dimensional electrons, which interact with longitudinal phonons via the deformation potential. The scattering potential of impurities, boundaries, and defects is modeled by quasistatic scatterers and vibrating scatterers, which move in the same way as host atoms. In thin films and nanostructures the phonons relax mainly in a substrate, and the phonon-drag thermopower substantially depends on the character of electron scatterers. Vibrating scatterers decrease thermopower, while static scatterers, such as rigid boundaries and heavy impurities, increase it. These changes in thermopower correlate to the disorder-induced modification of the electron-phonon relaxation rate. In bulk conductors, phonon-electron scattering dominates in the phonon relaxation, and the phonon-drag thermopower just slightly varies with electron mean free path.