Polaron stateについてII

熱的性質及び易動度

抄録

We have discussed polaron states at 0°K in the previous paper. In this paper we shall extend the variational technique, used in the previous paper, to polaron states at finite temperatures and discuss thermal properties and mobility of the polaron.
The lowest energy level of the polaron state is - hωα/ (2-nH) 1/2 and the effective mass m* of the polaron with small momentum is m (1+α/6 (2-n+1) 3/2), where -n=1/ehω/kT-1 and α is the coupling constant between electron and lattice vibrations, namely 1/hω e²/2 (2mω/h) (1/K₀-1/K). This means that at higher temperature the displacements of ions around the excess electron becomes smaller, and consequently the energy levels of the polaron state rise up, the effective mass becoming smaller.The polaron state seems to exist only at temperature lower than hω/K. The relaxation time τ of the polaron is calculated to be τ=3/2ωα (m/m*) 1/2 (ehω/kT-1) by perturbation method. The mobility of the polaron is e/m 3/2ωα (m/m*) 3/2 (ehω/kT-1).