Weyl hydrodynamics in a strong magnetic field

TL;DR

This paper investigates Weyl semimetals under strong magnetic fields, revealing anisotropic impurity scattering, hydrodynamic electron flow resembling Poiseuille flow, and calculating viscosity with temperature dependence, enabling experimental probing via thermal conductance.

Contribution

It provides a microscopic calculation of viscosity in Weyl liquids under magnetic fields and explores hydrodynamic transport regimes in Weyl semimetals.

Findings

Impurity scattering is anisotropic and suppressed when the magnetic field is perpendicular to Weyl node separation.

Electron flow in a strong magnetic field resembles Poiseuille flow in a pipe.

Viscosity weakly depends on magnetic field and scales as T^2 with temperature.

Abstract

We study the hydrodynamic transport of electrons in a Weyl semimetal in a strong magnetic field. Impurity scattering in a Weyl semimetal with two Weyl nodes is strongly anisotropic as a function of the direction of the field and is significantly suppressed if the field is perpendicular to the separation between the nodes in momentum space. This allows for convenient access to the hydrodynamic regime of transport, in which electron scattering is dominated by interactions rather than by impurities. In a strong magnetic field, electrons move predominantly parallel to the direction of the field, and the flow of the electron liquid in a Weyl-semimetal junction resembles the Poiseuille flow of a liquid in a pipe. We compute the viscosity of the Weyl liquid microscopically and find that it weakly depends on the magnetic field and has the temperature dependence $\eta(T)\propto T^2$. The hydrodynamic flow of the Weyl liquid can be generated by a temperature gradient. The hydrodynamic regime in a Weyl-semimetal junction can be probed via the thermal conductance $G_q(B,T)\propto B^2 T$ of the junction.