Dynamically tunable hydrodynamic transport in boron nitride-encapsulated graphene

TL;DR

This study demonstrates a method to dynamically tune hydrodynamic charge transport in graphene by using UV radiation and electric fields to control disorder levels, affecting thermal and electrical conduction properties.

Contribution

The paper introduces a reversible, in-situ technique to modulate disorder in graphene devices, enabling control over hydrodynamic transport regimes at room temperature.

Findings

UV radiation increases disorder and momentum relaxation.

Disorder tuning affects the Lorentz number and Wiedemann-Franz law adherence.

Transport properties can be reversibly controlled in graphene.

Abstract

Over the past decade, graphene has emerged as a promising candidate for exploring the viscous nature of electronic flow facilitated by the availability of extremely high-quality devices employing a graphene channel encapsulated within dielectric layers of hexagonal boron nitride (hBN). However, the level of disorder in such systems is mainly determined by the device fabrication protocols, making it impossible to obtain a tunability between the impurity-dominated and the viscous transport within the same device. In this work, using a combination of ultraviolet (UV) radiation and gate electric field, we have demonstrated a dynamic modulation of charge hydrodynamics, quantified in the thermal and electrical transport by the extent of departure from the Wiedemann-Franz (WF) Law in monolayer graphene devices at room temperature. We achieved this by tuning the disorder level continuously and reversibly using UV light to create transient trap states in the encapsulating hBN dielectric. With progressive UV radiation, we observed a dramatic increase in the momentum-relaxing scattering relative to that between the electrons and also the Lorentz number, by nearly a factor of ten, with increasing disorder, thereby approaching the restoration of the WF law in highly disordered graphene. Our experiments outline a potent strategy to tune the fundamental mechanism of charge flow in state-of-the-art graphene devices.