Remarkable thermoelectric performance in BaPdS$_2$ via pudding-mold band structure and ultralow lattice thermal conductivity

TL;DR

BaPdS$_2$ exhibits exceptional thermoelectric performance due to its pudding-mold electronic band structure and ultralow lattice thermal conductivity, making it a promising material for thermoelectric applications.

Contribution

This study demonstrates that BaPdS$_2$ naturally combines pudding-mold band structure and ultralow thermal conductivity, leading to high thermoelectric efficiency.

Findings

Peak figure of merit between 2 and 3 in certain directions

Large thermoelectric power factor due to pudding-mold band structure

Ultralow lattice thermal conductivity from anharmonic phonon interactions

Abstract

Efficient thermoelectric materials require a rare and contraindicated combination of materials properties: large electrical conductivity, large Seebeck coefficient, and low thermal conductivity. One strategy to achieve the first two properties is via low-energy electronic bands containing both flat and dispersive parts in different regions of crystal momentum space, known as a pudding-mold band structure. Here, we illustrate that BaPdS$_2$ successfully achieves the pudding-mold band structure, contributing to a large thermoelectric power factor, due to its anisotropic crystal structure containing zig-zag chains of edge-sharing square planar PdS$_4$ units. In addition, BaPdS$_2$ exhibits ultralow lattice thermal conductivity, and thus also achieves the third property, due to extremely soft and anharmonic interactions in its transverse acoustic phonon branch. We predict a remarkably large thermoelectric figure of merit, with peak values between 2 and 3 for two of the three crystallographic directions, suggesting BaPdS$_2$ warrants experimental investigation.