Viscous magnetoresistance of correlated electron liquids

Evidence for hydrodynamic flow of electrons was recently reported in a number of transport experiments in high-mobility semiconductor and graphene nanodevices. The electron liquid in these systems moves in the presence of a long-range disorder potential, which makes the entropy per electron position dependent. The resulting nonisentropic flow is markedly different from Stokesian flow: the resistivity is governed not only by the viscosity of the electron fluid but also by its thermal conductivity. Here, the authors show that the weak-field magnetoresistance (MR) in this hydrodynamic regime is caused by the modification of the flow pattern by the Lorentz force. The resulting MR is positive and is controlled by the shear viscosity alone. This may help separate the viscous and the thermal contributions to the resistivity.