Thermoelectric Effect in Mott Variable-Range Hopping

TL;DR

This paper investigates the thermoelectric response in disordered systems with Mott variable-range hopping, revealing a new temperature dependence of the Seebeck coefficient that aligns with experimental data.

Contribution

It introduces a revised theoretical expression for the low-temperature Seebeck coefficient in VRH systems, accounting for energy-dependent localization length.

Findings

Seebeck coefficient scales as T^{d/(d+1)} in VRH systems.

The new theoretical model matches experimental data for CuCrTiS4.

Contrasts with previous T^{(d-1)/(d+1)} dependence based on energy-independent localization length.

Abstract

On the basis of the Kubo-Luttinger linear response theory combined with the scaling theory of Anderson localization predicting the energy dependence of localization length near the mobility edge, we have studied the thermoelectric response of a disordered system exhibiting Mott variable-range hopping (VRH). We found that the low-tempetature Seebeck coefficient for VRH conduction in a $d$-dimensional system varies as $S\propto T^{d/(d+1)}$, which is different from the widely used expression, $S\propto T^{(d-1)/(d+1)}$, based on the energy-independent localization length. It is seen that the low-$T$ behavior of $S(T)$ of the thiospinel CuCrTiS$_4$ is in full agreement with the new scheme.