Thermoelectric Transport in Weyl Semimetal BaMnSb2: a First-Principles Study

TL;DR

This study uses first-principles calculations to analyze the thermoelectric properties of the topological semimetal BaMnSb2, revealing low thermal conductivity and unique directional conduction behaviors that could enhance thermoelectric performance.

Contribution

It provides a detailed theoretical investigation of BaMnSb2's electronic, phononic, and thermoelectric properties, highlighting its potential for thermoelectric applications and complex band structure effects.

Findings

BaMnSb2 exhibits low lattice thermal conductivity due to phonon scattering.

The material shows goniopolar transport with simultaneous n-type and p-type conduction.

Doping could improve thermoelectric efficiency by increasing the figure of merit.

Abstract

Topological materials are often associated with exceptional thermoelectric properties. Orthorhombic BaMnSb2 is a topological semimetal consisting of alternating layers of Ba, Sb, and MnSb. A recent experiment demonstrates that BaMnSb2 has a low thermal conductivity and modest thermopower, promising as a thermoelectric material. Through first-principles calculations with Coulomb repulsion and spin-orbit coupling included, we studied the electronic structure, phononic structure, and thermoelectric transport properties of BaMnSb2 in depth. We find that BaMnSb2 exhibits a low lattice thermal conductivity, owing to the scattering of the acoustic phonons with low-frequency optical modes. Using the linearized Boltzmann transport theory with a constant relaxation time approximation, the thermopower is further calculated and an intriguing goniopolar transport behavior, which is associated with both n-type and p-type conduction along separate transport directions simultaneously, is observed. We propose that the figure of merit can be enhanced via doping in which electrical conductivity is decreased while the thermopower remains undiminished. BaMnSb2 is a potential platform for elucidating complex band structure effects and topological phenomena, paving the way to explore rich physics in low-dimensional systems.