Hydrodynamic collective modes in graphene

TL;DR

This paper provides a comprehensive calculation of hydrodynamic collective modes in graphene, revealing how viscous effects influence sound modes and linking charge fluctuations with plasmons beyond the hydrodynamic regime.

Contribution

It offers the first unified analysis of dispersion relations for hydrodynamic modes in graphene, including viscous effects and their impact on collective excitations.

Findings

Hydrodynamic sound mode becomes overdamped at large momentum.

Charge density fluctuations are connected to plasmons beyond the hydrodynamic regime.

Viscous effects significantly alter collective mode behavior in graphene.

Abstract

Collective behavior is one of the most intriguing aspects of the hydrodynamic approach to electronic transport. Here we provide a consistent, unified calculation of the dispersion relations of the hydrodynamic collective modes in graphene. Taking into account viscous effects, we show that the hydrodynamic sound mode in graphene becomes overdamped at sufficiently large momentum scales. Extending the linearized theory beyond the hydrodynamic regime, we connect the diffusive hydrodynamic charge density fluctuations with plasmons.