Rational design of large anomalous Nernst effect in Dirac semimetals

TL;DR

This paper proposes a design principle for large anomalous Nernst effect in Dirac semimetals, demonstrating how Zeeman fields and specific band structures can enhance the effect for energy conversion applications.

Contribution

It introduces a theoretical framework and first-principles calculations showing how Dirac semimetals can be engineered for enhanced anomalous Nernst conductivity using Zeeman fields.

Findings

Double-peak anomalous Hall conductivity in Dirac nodes under Zeeman field

Na3Bi and NaTeAu exhibit sizable ANC near Fermi level

Design principle for enhanced ANC pinning at Fermi level

Abstract

Anomalous Nernst effect generates a transverse voltage perpendicular to the temperature gradient. It has several advantages compared with the longitudinal thermoelectricity for energy conversion, such as decoupling of electronic and thermal transports, higher flexibility, and simpler lateral structure. However, a design principle beyond specific materials systems for obtaining a large anomalous Nernst conductivity (ANC) is still absent. In this work, we theoretically demonstrate that a pair of Dirac nodes under a Zeeman field manifests a double-peak anomalous Hall conductivity curve with respect to the chemical potential and a compensated carriers feature, leading to an enhanced ANC pinning at the Fermi level compared with that of a simple Weyl semimetal with two Weyl nodes. Based on first-principles calculations, we then provide two Dirac semimetal candidates, i.e., Na3Bi and NaTeAu, and show that under a Zeeman field they exhibit a sizable ANC value of 0.4 A/(m*K) and 1.3 A/(m*K), respectively, near the Fermi level. Our work provides a design principle with a prototype band structure for enhanced ANC pinning at Fermi level, shedding light on the inverse design of other specific functional materials base on electronic structure.