Para-hydrodynamics from weak surface scattering in ultraclean thin flakes

Abstract

Electron hydrodynamics typically emerges in electron fluids with a high electron-electron collision rate. However, new experiments with thin flakes of WTe${}_2$ have revealed that other momentum-conserving scattering processes can replace the role of the electron-electron interaction, thereby leading to a novel, so-called para-hydrodynamic regime. Here, we develop the kinetic theory for para-hydrodynamic transport. To this end, we consider a ballistic electron gas in a thin 3-dimensional sheet where the momentum-relaxing (${\ell }_{mr}$) and momentum-conserving (${\ell }_{mc}$) mean free paths are decreased due to boundary scattering from a rough surface. The resulting effective mean free path of the electronic flow is then expressed in terms of microscopic parameters of the sheet boundaries, predicting that a para-hydrodynamic regime with ${\ell }_{mr}\gg {\ell }_{mc}$ emerges generically in ultraclean three-dimensional materials. Using our approach, we recover the transport properties of WTe${}_2$ in the para-hydrodynamic regime in good agreement with existing experiments.

6+6 pages, 6 figures. The published v2 contains only minor changes

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Cited by in corpus (2)

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• Hydrodynamics of the electronic Fermi liquid: a pedagogical overview