Thermoelectric prospects of nanomaterials with spin-orbit surface bands

TL;DR

This paper explores how nanostructuring thermoelectric materials like bismuth and bismuth telluride enhances their low-temperature thermoelectric performance through surface electronic transport and boundary phonon scattering effects.

Contribution

It demonstrates that surface electronic transport in nanowires significantly improves thermoelectric efficiency at low temperatures, supported by experimental and theoretical analysis.

Findings

Surface thermopower dominates below 100 K in Bi nanowires.

Surface transport and boundary phonon scattering enhance thermoelectric performance.

Comparison shows potential for other thermoelectric nanomaterials.

Abstract

Nanostructured composites and nanowire arrays of traditional thermoelectrics like Bi, Bi(1-x)Sb(x) and Bi(2)Te(3) have metallic Rashba surface spin-orbit bands featuring high mobilities rivaling that of the bulk for which topological insulator behavior has been proposed. Nearly pure surface electronic transport has been observed at low temperatures in Bi nanowires with diameter around the critical diameter, 50 nm, for the semimetal-to semiconductor transition. The surface contributes strongly to the thermopower, actually dominating for temperatures T < 100 K in these nanowires. The surface thermopower was found to be -1 T microvolt/(K^2), a value that is consistent with theory. We show that surface electronic transport together with boundary phonon scattering leads to enhanced thermoelectric performance at low temperatures of Bi nanowire arrays. We compare with bulk n-BiSb alloys, optimized CsBi(4)Te(6) and optimized Bi(2)Te(3). Surface dominated electronic transport can be expected in nanomaterials of the other traditional thermoelectrics.