Giant thermoelectric power factor in charged ferroelectric domain walls of GeTe with Van Hove singularities

Abstract

Abstract Increasing the Seebeck coefficient S in thermoelectric materials usually drastically decreases the electrical conductivity σ, making significant enhancement of the thermoelectric power factor σ S 2 extremelly challenging. Here we predict, using first-principles calculations, that the extraordinary properties of charged ferroelectric domain walls (DWs) in GeTe enable a five-fold increase of σ S 2 in the DW plane compared to bulk. The key reasons for this enhancement are the confinement of free charge carriers at the DWs and Van Hove singularities in the DW electronic band structure near the Fermi level. These effects lead to an increased energy dependence of the DW electronic transport properties, resulting in more than a two-fold increase of S with respect to bulk, without considerably degrading the in-plane σ. We propose a design of a nano-thermoelectric device that utilizes the exceptional thermoelectric properties of charged ferroelectric DWs. Our findings should inspire further investigation of ferroelectric DWs as efficient thermoelectric materials.