Magneto-thermoelectricty of anisotropic two-dimensional materials

TL;DR

This paper develops an exact analytical framework using the vector mean free path to study magneto-thermoelectric effects in anisotropic 2D materials, revealing limitations of conventional methods and analyzing specific electronic systems.

Contribution

It introduces a systematic approach based on the vector mean free path for accurate magneto-thermoelectric response calculations in anisotropic 2D materials.

Findings

Exact solutions for longitudinal and Hall conductivities

Analysis of Seebeck and Nernst coefficients in specific systems

Identification of limitations in relaxation-time approximation

Abstract

We use semiclassical Boltzmann transport theory to analytically study the electronic contribution to the linear thermoelectric response of anisotropic two-dimensional materials subjected to a perpendicular magnetic field. Conventional methods, such as the relaxation-time approximation within the Boltzmann formalism, often yield qualitatively incorrect results when applied to anisotropic mediums. On the other hand, the vector mean free path provides exact solutions for the linearized Boltzmann transport equation, and in principle, we can systematically evaluate it to any desired order in the external magnetic field. After laying out the general formalism of the magneto-thermoelectric responses of anisotropic systems based on the vector mean free path approach, we study the longitudinal and Hall charge conductivities, as well as the Seebeck and Nernst coefficients of two representative anisotropic two-dimensional electronic systems: a semi-Dirac semimetal and a two-dimensional system of tilted massless Dirac fermions.