Entropy Wave Instability in Dirac and Weyl Semimetals

TL;DR

This paper investigates hydrodynamic instabilities in Dirac and Weyl semimetals, revealing a novel entropy wave instability alongside the known Dyakonov-Shur instability, driven by relativisticlike electron behavior and boundary conditions.

Contribution

It introduces the entropy wave instability in Dirac and Weyl semimetals, highlighting its dependence on system size and flow velocity, distinct from traditional plasma instabilities.

Findings

Discovery of entropy wave instability in 2D and 3D systems.

Entropy wave instability frequency is tunable by system size and flow velocity.

Both instabilities occur for opposite flow directions.

Abstract

Hydrodynamic instabilities driven by a direct current are analyzed in 2D and 3D relativisticlike systems with the Dyakonov-Shur boundary conditions supplemented by a boundary condition for temperature. Besides the conventional Dyakonov-Shur instability for plasmons, we find an entropy wave instability in both 2D and 3D systems. The entropy wave instability is a manifestation of the relativisticlike nature of electron quasiparticles and a nontrivial role of the energy current in such systems. These two instabilities occur for the opposite directions of fluid flow. While the Dyakonov-Shur instability is characterized by the plasma frequency in 3D and the system size in 2D, the frequency of the entropy wave instability is tunable by the system size and the flow velocity.