Micromagnets dramatically enhance effects of viscous hydrodynamic flow in a two-dimensional electron fluid

The hydrodynamic behavior of electron fluids in a certain range of temperatures and densities is well established in graphene and in two-dimensional semiconductor heterostructures. The hydrodynamic regime is intrinsically based on electron-electron interactions, and therefore it provides a unique opportunity to study electron correlations. Unfortunately, in simple longitudinal resistance measurements, the relative contribution of hydrodynamic effects to transport is rather small, especially at higher temperatures. Viscous hydrodynamic effects are masked by impurities, interaction with phonons, uncontrolled boundaries, and ballistic effects. This essentially limits the accuracy of measurements of electron viscosity. Fundamentally, what causes viscous friction in the electron fluid is the property of the flow called vorticity. In this paper, we propose to use micromagnets to increase the vorticity by orders of magnitude. Experimental realization of this proposal will bring electron hydrodynamics to a qualitatively new precision level, as well as opening a new way to characterize and externally control the electron fluid.