Transverse voltage in anisotropic hydrodynamic conductors

In ultra-clean metals, weak momentum dissipation gives rise to non-Ohmic current flows, including both ballistic and hydrodynamic regimes. Hydrodynamic flow has gained attention for revealing electronic correlations and long-lived collective modes in quantum materials. However, distinguishing it from ballistic transport is difficult since both can show similar current distributions despite different underlying mechanisms. Using kinetic Boltzmann theory, we propose that the transverse channel voltage at zero magnetic field is an effective detector for hydrodynamic flow. The interplay between anisotropic fermiology and boundary scattering can lead to a characteristic sign change of the transverse voltage in certain materials systems.