Anisotropic Hydrodynamics in Quantum Hall Fluids with Tilted Field

We examine the hydrodynamics of electrons confined in a 2D quantum well the presence of a tilted magnetic field. We first compute the viscoelastic response functions of the electron fluid perturbatively in the strength of the tilted magnetic field. Next, by analyzing the semiclassical equations of motion, we identify how the corresponding tilt in the Landau orbits introduces anisotropy to the viscoelastic response of the electron fluid via the coupling of slow in-plane and fast out-of-plane degrees of freedom. By integrating out the out-of-plane degrees of freedom, we derive an effective two dimensional description of the dynamics. We show that there is a crossover as a function of temperature between anisotropic flow at low temperature to isotropic flow at high temperature. Finally, we remark on the experimental implications for integer quantum Hall devices.