A current amplifier operating in the ballistic and hydrodynamic transport regimes

The momentum-relaxing length scale (due to electron-phonon, electron-defect scattering) in two-dimensional carrier systems can be as large as microns, leading to a breakdown of diffusive transport in micron-scale devices. Depending on the strength of momentum-conserving electron-electron scattering, transport in the device can either be ballistic or hydrodynamic. The ballistic regime is characterized by electrons scattering predominantly against the device boundaries, whereas the hydrodynamic regime sets in when electron-electron scattering is sufficiently strong. Both regimes have distinct nonlocal current-voltage relationships, which have been used in several experiments (e.g., in graphene, GaAs/AlGaAs) to detect the departure from diffusive transport. We now exploit the nonlocality inherent in both regimes to design a current amplifier. The amplification is determined by the device geometry, and scales linearly with the appropriate device-scale. We showcase the striking non-diffusive current flow in the amplifier. The operational principle, based on nonlocality, is distinct from previous amplification methods based on nonlinear current-voltage relations (such as the Venturi effect).