Photogalvanic effect in hydrodynamic flows of nonreciprocal electron liquids
We study nonlinear hydrodynamic electron transport driven by an AC electric field. In noncentrosymmetric conductors with broken time-reversal (TR) symmetry the nonlinear flow of such liquids is nonreciprocal, giving rise to a DC current $I^{DC}$ that is quadratic in the amplitude of the AC electric field. This is the hydrodynamic analogue of the linear photogalvanic effect (PGE), which arises in bulk noncentrosymmetric materials with broken TR symmetry. The magnitude of $I^{DC}$ depends on both the properties of the electron fluid and the geometry of the flow, and may be characterized by two dimensionless parameters: the nonreciprocity number $\mathcal{N}$, and the frequency-dependent vibrational number $\mathcal{R}$. Due to nonlocality of hydrodynamic transport, at low frequencies of the AC drive, $I^{DC}$ is super-extensive. The AC component of the electric current is likewise strongly affected by nonreciprocity: the hysteretic current-voltage dependence becomes skewed, which can be interpreted in terms of nonreciprocity of the memory retention time.