Abstract: | We study IR polarized reflection spectra of solid solutions (Bi2−x
Sb
x
)Te3 (0 < x < 1) in the temperature range 78–293 K and in the excitation range of plasma oscillations of free charge carriers. We reveal
that, as the content of Sb2Te3 in the solid solution increases from 0 to 50%, the anisotropy of both plasma frequencies and magnetic susceptibility vary
insignificantly. This indicates that, at 293 K, these crystals do not show significant changes in the composition of groups
of free carriers near the chemical potential level. We have found that to describe the observed anisotropy of plasma frequencies,
it is necessary to take into account the effect of heavy holes of the valence band. This is also confirmed by the results
of the study of the temperature behavior of plasma reflection spectra, which exhibit regularities that are similar to anomalous
temperature changes of the Hall coefficient. We show that a decrease in plasma frequencies with increasing temperature cannot
be described by an increase in the effective mass of charge carriers in accordance with the expression m* ∼ T
0.17, which was obtained upon interpretation of temperature dependences of a number of kinetic coefficients. We use the empirical
Moss rule ɛ∞2
E
g
to estimate the rate of decrease of the thermal band gap dE
g
/dT = −1.6 × 10−4 eV/deg in a crystal that contains 25% Sb2Te3. |