signatures of phonon-mediated hydrodynamic transport in semimetals

Hydrodynamic electron flow in condensed matters has been one of the most active research areas recently, where many open questions regarding the underlying mechanisms still remain. We utilize ab initio techniques to treat the electron scattering events explicitly, and show in combination with Boltzmann transport equation a more applicable metric of hydrodynamic transport taking into account temperature, channel width, and impurity length, which can be directly verified by various experimental techniques. By investigating different scattering lengthscales in PdCoO2, ZrSiS, and TaAs2, we show that that phonon mediated electron-electron interaction could lead to much shorter momumtem conserving mean free path, facilitating hydrodynamic behavior in systems where the direct Coulomb interaction is largely screened.
Our findings show that key ingredients to achieve optimal hydrodynamic effect include high mobility carriers, low density of states compensated systems, and large electron-phonon matrix elements. The plethora of low symmetry crystals whose Fermi surfaces are composed of d orbitals from the transition metal and p orbitals from the metalloids provides a much larger pool for further study. This work offers insights into study of electron interactions through transport phenomena.