The Contribution of Quasi-Transverse Phonons in the Electron–Phonon Drag Thermopower in Noble Metals

The impact of elastic energy anisotropy on the drag thermopower in noble metals at low temperatures has been investigated. In order to describe the interaction of electrons with longitudinal phonons, the strain potential theory has been employed. In calculating electron relaxation on shear components of vibrational modes, the electron–phonon interaction constant, previously determined from a comparison of the calculated electrical resistivity of Au, Ag, and Cu bulk crystals with experimental data, was used. The maximum values of the drag thermopower in perfect noble metal crystals have been determined. These values are independent of the electron–phonon interaction constants; rather, they are determined by the elastic moduli of the second order, crystal density, and electron concentration. It has been demonstrated that quasi-transverse phonons constitute predominant contribution to the drag thermopower at low temperatures, whereas the contribution of longitudinal phonons were found to be negligible. At the same time, for perfect Au, Ag, and Cu crystals, the dominant contribution to the electron–phonon drag is provided by the slow t2-mode.