Unconventional thermoelectric behaviors and enhancement of figure of merit in Rashba spintronic systems

TL;DR

This study investigates thermoelectric transport in Rashba spintronic systems, revealing unconventional behaviors and significant enhancements in thermoelectric efficiency near the band crossing point due to unique density of states and scattering mechanisms.

Contribution

It provides an exact solution to thermoelectric transport in Rashba systems, uncovering novel behaviors and enhancement mechanisms not captured by previous approximations.

Findings

Electrical conductivity is Drude-like above the band crossing point.

Thermopower and figure of merit are strongly enhanced below the band crossing point.

Breakdown of the Mott relation near the band crossing point.

Abstract

Thermoelectric transport in strongly spin-orbit coupled two-dimensional Rashba system is studied using the exact solution of the linearized Boltzmann equation. Some unusual transport behaviors are revealed. We show that the electrical conductivity takes a Drude form when the Fermi energy $E_{F}$ is above the band crossing point, but a non-Drude form which is a quadratic function of $E_{F}$ when $E_{F}$ lies below the band crossing point. The Mott relation breaks down when $E_{F}$ lies in the vicinity of the band crossing point. It is shown that the thermopower and thermoelectric figure of merit are strongly enhanced when $E_{F}$ downs below the band crossing point. This enhancement is attributed to not only the one-dimensional-like density of state but also the unconventional intraband elastic scattering below the band crossing point. The differences between these results and those obtained by the relaxation time approximation are discussed in detail.