Temperature Dependence of Electron Viscosity in Superballistic GaAs Point Contacts

Hydrodynamic description of collective electron motion turns out to be fruitful, since it provides a reliable physical concept that allows engineering the electron-electron interaction. We experimentally study the relation between two fundamental quantities-the electron viscosity and the Fermi quasiparticle lifetime-beyond the applicability limit of the Fermi liquid theory. We use point contact (PC) geometry to study electron transport and observe superballistic PC conductance, which is a signature of the electron viscosity. At high enough temperatures, the viscosity-lifetime relation is shown to diverge from the theoretically predicted one and turns out to be nontrivial. In addition, we study these phenomena in PCs freely suspended over a substrate, i.e., under the unique experimental conditions of enhanced electron-electron interaction. Suspension is found to reduce the electron viscosity in the whole temperature range, which makes the suspended structures a promising test bed for studying hydrodynamic effects in solids.