Nonreciprocity of Hydrodynamic Electron Transport in Noncentrosymmetric Conductors

We show that the nonreciprocity of hydrodynamic electron transport in noncentrosymmetric conductors with broken time-reversal symmetry is significantly enhanced compared to the disorder-dominated regime. This enhancement is caused by the linear dependence of the viscosity of the electron liquid on the flow velocity, which is allowed in the absence of time-reversal symmetry and Galilean invariance. The resulting nonlinear flows break dynamical similarity, and, thus, in addition to the Reynolds number, they are characterized by a second dimensionless parameter, the nonreciprocity number. The latter is linear in velocity but independent of system size. We determine the nonlinear conductance of a Hall bar and show that the nonreciprocal correction to the current can be of comparable magnitude to its reciprocal counterpart.