Anomalous heat flow in 8-$Pmmn$ borophene with tilted Dirac cones

TL;DR

This paper demonstrates an anomalous thermal Hall effect in 8-Pmmn borophene caused by tilted Dirac cones and circularly polarized light, revealing potential for thermal control in 2D materials.

Contribution

It analytically establishes the thermal Hall effect in borophene with tilted Dirac cones under circular polarization, linking anisotropy, tilt, and Berry curvature to heat flow.

Findings

Thermal Hall conductivity depends on Dirac cone tilt and anisotropy.

Circularly polarized light induces a gap and Berry curvature in borophene.

Thermal rectification can be achieved by switching light polarization.

Abstract

We analytically establish an anomalous transverse flow of heat in 8-\textit{Pmmn} borophene, one of the several two-dimensional (2D) allotropes of Boron (B). The dispersion of this allotrope contains a pair of anisotropic and tilted Dirac cones which are gapped by placing the 2D \textit{B} sheet under an intense circularly-polarized illumination. A gap in the Dirac dispersion leads to a finite Berry curvature and connected anomalous Hall effects. In the case of thermoelectrics, this manifests as a heat current perpendicular to the temperature gradient - the thermal Hall effect. A quantitative calculation of the attendant thermal Hall conductivity reveals dependence on the intrinsic anisotropy and tilt of the Dirac cone. Further, by estimating the longitudinal thermal conductivity using the Weidemann-Franz law, we also outline steps to compute the thermal Hall angle that gauges the generation efficiency of such transverse heat processes. Finally, we touch upon the idea of thermal rectification wherein the direction of flow of the anomalous heat reverses through a simple switch of the polarization of incident light and is of interest in thermal logic circuits.