Berry curvature and Hall viscosities in an anisotropic Dirac semi-metal

TL;DR

This paper explores parity-odd transport phenomena in an anisotropic Dirac semi-metal, deriving new expressions for Hall viscosities and revealing multiple independent odd viscosity coefficients due to anisotropy.

Contribution

It introduces a method to calculate Berry curvature in anisotropic Dirac systems and derives multiple odd viscosities, expanding understanding beyond rotationally invariant models.

Findings

Derived Berry curvature for anisotropic Dirac semi-metal

Identified two independent odd viscosity coefficients

Found one odd viscosity coefficient to be zero

Abstract

We investigate parity-odd non-dissipative transport in an anisotropic Dirac semi-metal in two spatial dimensions. The analysis is relevant for interacting electronic systems with merging Dirac points at charge neutrality. For such systems the dispersion relation is relativistic in one direction and non-relativistic in the other. We give a proposal how to calculate the Berry curvature for this system and use it to derive more than one odd viscosities, in contrast to rotationally invariant systems. We observe that in such a model the odd part of stress tensor is parameterised by two independent transport coefficients and one that is identically zero.