Extraordinary Thermoelectric Properties of Topological Surface States in Quantum-Confined Cd3As2 Thin Films

TL;DR

This study reveals that quantum-confined Cd3As2 thin films exhibit enhanced thermoelectric effects at cryogenic temperatures, primarily due to topological surface states, opening new avenues for low-temperature energy applications.

Contribution

It provides the first systematic analysis linking topological surface states to enhanced thermoelectric properties in Cd3As2 thin films.

Findings

Significant Seebeck and Nernst effects at cryogenic temperatures.

Surface states dominate thermoelectric transport in thin films.

Potential for high-performance cryogenic thermoelectric devices.

Abstract

Topological insulators and semimetals have been shown to possess intriguing thermoelectric properties promising for energy harvesting and cooling applications. However, thermoelectric transport associated with the Fermi arc topological surface states on topological Dirac semimetals remains less explored. In this work, we systematically examine thermoelectric transport in a series of topological Dirac semimetal Cd3As2 thin films grown by molecular beam epitaxy. Surprisingly, we find significantly enhanced Seebeck effect and anomalous Nernst effect at cryogenic temperatures when the Cd3As2 layer is thin. Combining angle-dependent quantum oscillation analysis, magnetothermoelectric measurement, transport modelling and first-principles simulation, we isolate the contributions from bulk and surface conducting channels and attribute the unusual thermoeletric properties to the topological surface states. Our analysis showcases the rich thermoelectric transport physics in quantum-confined topological Dirac semimetal thin films and suggests new routes to achieving high thermoelectric performance at cryogenic temperatures.