Peculiarities of the behavior of the temperature dependence of high-frequency conductivity of disordered semiconductors in the terahertz frequency range

The analysis of the features of electron hopping transport in the impurity band of a disordered semiconductor with hydrogen-like impurities, associated with the behavior of the temperature dependence of high-frequency conductivity in the low-temperature region, is carried out. Based on the pair approximation, the numerical calculation of the temperature dependence of the real part of the high-frequency conductivity of a disordered semiconductor in the terahertz frequency range was performed, in which the transition from an almost linear to a quadratic frequency dependence of the real part of the conductivity was observed under low-temperature conditions with increasing frequency. It is shown that taking into account the Coulomb interaction between electrons in pairs causes a non-monotonic saturation of the temperature dependence of high-frequency conductivity with decreasing temperature due to the opposite direction of changes in the relaxation and resonance contributions to conductivity with changing temperature. The increase in phononless conductivity with decreasing temperature is due to the main role of the Coulomb interaction between electrons in resonant pairs at low temperatures, $e^2/kr_\omega>\hbar\omega$ ($r_\omega$ – optimal hopping distance at frequency $\omega$).