Electronic Viscous Flow in Hexagonal Boron Nitride Encapsulated Graphene FETs

In most conductors, electron transport primarily involves diffusive scattering from defects and interactions with lattice vibrations (phonons), resulting in Ohmic behavior. Alternatively, transport can become ballistic when the dimensions of the conducting channel become the smallest length scale in the system. However, an intriguing and relatively unexplored transport regime emerges when electron-electron interactions attain a level of strength where they induce correlated and momentum-conserving flow, akin to the Hagen-Poiseuille flow observed in classical fluids.<br/>Our research explores the fascinating realm of charge hydrodynamic transport effects, which unveil unique characteristics. These include width-dependent channel conductivity and a significant reduction in resistivity at elevated electron temperatures. Furthermore, we observe the presence of charge vortices through non-local vicinity resistance measurements[1]. By combining various approaches, we validate the existence of viscous effects over a wide temperature range, extending even up to room temperature. This resilience of hydrodynamic transport in graphene, compared to other systems like two-dimensional electron gases (2DEGs) and WP₂, is a notable finding.<br/>To underpin our experimental findings, we employ finite element calculations of the graphene channel. These calculations not only confirm our observations but also provide valuable insights into device geometries that can enhance viscous effects. The occurrence of viscous effects at room temperature opens up new possibilities for functional hydrodynamic devices, including geometric rectifiers like a Tesla valve and charge amplifiers based on the electronic Venturi effect. This research signifies a step forward in understanding and harnessing the potential of charge hydrodynamics in graphene-based systems.<br/><br/>Reference:<br/>[1]. W. Huang, T. Paul, K. Watanabe, T. Taniguchi, M. L. Perrin, and M. Calame, Phys. Rev. Research 5, 023075