Nonlinear current-voltage characteristics of mesoscopic structures in non-equilibrium ballistic transport

Advances in materials have allowed for the suppression of momentum relaxing electron-phonon and defect scattering in very clean material systems such as graphene and semiconductor heterostructure based 2D electron systems (2DESs). This has led to the study of the hydrodynamic and ballistic transport regimes where the dominant interactions in the system are electron-electron scattering and electron-device wall collisions. We consider mesoscopic structures in an ultra-high mobility GaAs/AlGaAs 2DES initially in the ballistic regime at low temperature. Increasing the bias current across the structures can result in heating of the electron system due to injection of high energy electrons. This leads to a ballistic-hydrodynamic regime transition, which manifests itself as a deviation from linearity in the current-voltage characteristics of the structures. We present nonlinear current-voltage characteristics in both 2- and 4-probe configurations in several progressively complex mesoscopic geometries and point contacts under non-equilibrium transport. The possible origin of the nonlinearities and their association with the Gurzhi hydrodynamic effect will be discussed.