Transverse thermoelectric conversion in the mixed-dimensional semimetal WSi$_2$

TL;DR

This study demonstrates transverse thermoelectric conversion in WSi₂ crystals with axis-dependent conduction, revealing the role of mixed-dimensional electronic structures and sample-dependent scattering in enabling potential thermoelectric applications.

Contribution

The paper provides experimental evidence and computational analysis showing that WSi₂ exhibits transverse thermoelectric effects due to its unique mixed-dimensional electronic structure and band-dependent scattering.

Findings

Transverse thermoelectric effect observed in WSi₂ with rotated temperature gradient.

Sample-dependent transport properties linked to band-dependent scattering.

Mixed-dimensional electronic structure is key for axis-dependent conduction polarity.

Abstract

Materials with axis-dependent conduction polarity are known as $p\times n$-type or goniopolar conductors that can be used for transverse thermoelectric devices, allowing the longitudinal thermal current to be converted into the transverse electrical current. Here, we performed experimental and computational studies on the transport properties of WSi$_2$ single crystals, in which such axis-dependent conduction polarity of the thermopower and the Hall coefficient have recently been reported, and demonstrated the transverse thermoelectric effect by applying the temperature gradient in a 45$^{\circ}$ rotated direction from the crystallographic axis. We have observed strongly sample-dependent transport properties, which have also been observed in previous studies, and together with first-principles calculations we show that such sample-dependent transport properties originate from the band-dependent scattering rates of carriers. The calculated band-resolved Peltier conductivity shows that the mixed-dimensional electronic structure consisting of a quasi-one-dimensional electron Fermi surface and a quasi-two-dimensional hole surface is a key property for the axis-dependent conduction polarity. The directly obtained transverse thermoelectric figure of merit is comparable to that of the anomalous Nernst materials, implying that the present material is a potential candidate for transverse thermoelectric conversion.