# Screening and plasma oscillations in an electron gas in the hydrodynamic approximation

## TL;DR

This paper develops a hydrodynamic model for screening and plasma oscillations in electron gases across various dimensions, revealing that long-wavelength plasma oscillations are classical phenomena unaffected by quantum effects, regardless of the material's dispersion law.

## Contribution

It provides a unified hydrodynamic framework for screening in electron gases that clarifies the classical nature of plasma oscillations across different dimensionalities and material types.

## Key findings

- Plasma oscillations are classical phenomena with no explicit quantum effects.
- The oscillation character depends solely on dimensionality and equation of state.
- Materials with Dirac dispersion, like graphene, follow the same classical behavior.

## Abstract

A hydrodynamic theory of screening in a generic electron gas of arbitrary dimensionality is given that encompasses all previously studied cases and clarifies the predictions of the many-body approach. We find that long-wavelength plasma oscillations are classical phenomena with quantum-mechanical effects playing no explicit role. The character of the oscillations is solely dictated by the dimensionality of the electron system and its equation of state in the neutral limit. Materials whose excitations are described by the Dirac dispersion law -- such as doped graphene or a Weyl semimetal -- are no exception to this rule.