Hydrodynamics of electrons in graphene

TL;DR

This paper reviews recent advances in understanding how electrons in graphene behave like a fluid, highlighting experimental observations, theoretical derivations, and implications for electronic transport.

Contribution

It provides a comprehensive overview of the hydrodynamic behavior of electrons in graphene, combining phenomenological and kinetic theory approaches, and discusses experimental evidence.

Findings

Hydrodynamic electron flow observed in graphene transport measurements

Derivation of hydrodynamics from kinetic theory and phenomenology

General framework applicable to other materials

Abstract

Generic interacting many-body quantum systems are believed to behave as classical fluids on long time and length scales. Due to rapid progress in growing exceptionally pure crystals, we are now able to experimentally observe this collective motion of electrons in solid-state systems, including graphene. We present a review of recent progress in understanding the hydrodynamic limit of electronic motion in graphene, written for physicists from diverse communities. We begin by discussing the "phase diagram" of graphene, and the inevitable presence of impurities and phonons in experimental systems. We derive hydrodynamics, both from a phenomenological perspective and using kinetic theory. We then describe how hydrodynamic electron flow is visible in electronic transport measurements. Although we focus on graphene in this review, the broader framework naturally generalizes to other materials. We assume only basic knowledge of condensed matter physics, and no prior knowledge of hydrodynamics.