Nonlinear charge and thermal transport properties induced by orbital magnetic moment in chiral crystal cobalt monosilicide

TL;DR

This paper investigates nonlinear charge and thermal Hall effects in cobalt monosilicide, revealing significant responses linked to exotic fermions and orbital magnetic moments, expanding understanding of transport phenomena in chiral crystals.

Contribution

It provides the first quantitative analysis of NCTE charge and thermal Hall effects in B20-type compounds, highlighting their enhancement near RSW fermions and spin-1 excitations.

Findings

NCTE charge and thermal Hall currents are measurable along [111] direction.

Responses are enhanced around RSW fermions and spin-1 excitations.

Orbital magnetic moments solely govern the NCTE Hall effect in this material.

Abstract

The existence of exotic singularities in momentum space, such as spin-1 excitations and Rarita-Schwinger-Weyl (RSW) fermions, has been discussed so far to explore unique phenomena in the nonmagnetic B20-type compounds. Meanwhile, the Nonlinear Thermo-Electric (NCTE) charge and thermal Hall effect, a response proportional to the cross product of the electric field and temperature gradient, is expected in this chiral material, yet remains unexplored in B20-type compounds. Here, based on $ab \ initio$ calculations and symmetry analysis, we quantitatively analyze the NCTE charge and thermal Hall effects in cobalt monosilicide, obtaining experimentally measurable values of NCTE charge and thermal Hall current along [111] direction, which is not expected for second-order current responses to the DC electric field. Furthermore, we demonstrate that these significant responses are enhanced around RSW fermions and spin-1 excitations. Additionally, we clarify that the NCTE Hall effect is solely governed by orbital magnetic moments due to the cancellation of Berry curvature contributions in cubic chiral crystals.