Temperature-dependent electron mobility and large polaron interpretation inBi12SiO20

Abstract

The electron band mobility in ${\mathrm{Bi}}_{12}{\mathrm{SiO}}_{20}$ is determined down to 100 K by the holographic time of flight method. Data are presented for different crystals of different origins in the temperature range between 100 and 500 K. The observed mobility rises from $\ensuremath{\sim}1.7{\mathrm{cm}}^{2}{\mathrm{V}}^{\ensuremath{-}1}{\mathrm{s}}^{\ensuremath{-}1}$ at 500 K to $\ensuremath{\sim}10{\mathrm{cm}}^{2}{\mathrm{V}}^{\ensuremath{-}1}{\mathrm{s}}^{\ensuremath{-}1}$ at 190 K, and decreases again at lower temperature. We show that the data correspond to an intrinsic band mobility between 190 and 500 K. The temperature dependence of the mobility can be reproduced in this temperature range with a large polaron model that derives all its parameters from the experimental phonon spectrum of the material. A deviation from the large polaron prediction that takes place between 250 and 190 K, depending on the sample, can be ascribed to the influence of defects or impurities.