Nonmonotonic temperature dependence of electron viscosity and crossover to high-temperature universal viscous fluid in monolayer and bilayer graphene

Electrons in quantum matter behave like a fluid when the quantum-mechanical carrier-carrier scattering dominates over other relaxation mechanisms. By combining a microscopic treatment of electron-electron interactions within the random phase approximation with a phenomenological Navier-Stokes-like equation, we predict that in the limit of high temperature and strong Coulomb interactions, both monolayer graphene and bilayer graphene exhibit a universal behavior in dynamic viscosity. We find that the dynamic viscosity to entropy density ratio for bilayer graphene is closer to the holographic bound, suggesting that such a bound might be observable in a condensed matter system. We discuss how this could be observed experimentally using magnetoconductance measurements in a Corbino geometry for a realistic range of temperature and carrier density.