Coupled electron-phonon hydrodynamics in two-dimensional semiconductors

TL;DR

This paper reveals that in 2D semiconductors, strong electron-phonon interactions can lead to a coupled hydrodynamic transport regime with low dissipation, enhancing charge transport despite the interactions.

Contribution

It introduces the concept of coupled electron-phonon hydrodynamics in 2D semiconductors, showing how momentum circulation reduces dissipation and improves transport properties.

Findings

Momentum circulation leads to weak dissipation in coupled systems

Hydrodynamic transport regime enhances charge mobility

Low-dissipation transport occurs despite strong interactions

Abstract

Electronic and thermal transport properties in two-dimensional (2D) semiconductors have been extensively investigated due to their potential to miniaturize transistors. Microscopically, electron-phonon interactions are considered the dominant momentum relaxation mechanism for electrons that limits carrier mobility beyond cryogenic temperatures. However, when electrons and phonons are considered as a single system, electron-phonon interactions conserve the total momentum and energy, leading to the possibility of low-dissipation transport. In this work, we systematically investigate the momentum circulation between electrons and phonons and its impact on carrier transport properties in 2D semiconductors given their strong electron-phonon interactions. We find that, when momentum circulation is taken into account, the total momentum in the coupled electron-phonon system is weakly dissipated, leading to a coupled electron-phonon hydrodynamic transport regime, in which electrons and phonons exhibit a joint drift motion rather than separate diffusive behaviors. In this new transport regime, charge transport properties are significantly enhanced. Contrary to previous belief, our results demonstrate that low-dissipation charge transport can occur despite strong electron-phonon interactions when there is effective momentum circulation between electrons and phonons mediated by the strong interactions. Our work advances fundamental understandings of carrier transport in 2D semiconductors.