Thermal and electrical signatures of a hydrodynamic electron fluid in tungsten diphosphide

摘要

Materials with strongly-correlated electrons exhibit interesting phenomenasuch as metal-insulator transitions and high-temperature superconductivity. Instark contrast to ordinary metals, electron transport in these materials isthought to resemble the flow of viscous fluids. Despite their differences, itis predicted that transport in both, conventional and correlated materials, isfundamentally limited by the uncertainty principle applied to energydissipation. Here we discover hydrodynamic electron flow in the Weyl-semimetaltungsten phosphide (WP2). Using thermal and magneto-electric transportexperiments, we observe the transition from a conventional metallic state, athigher temperatures, to a hydrodynamic electron fluid below 20 K. Thehydrodynamic regime is characterized by a viscosity-induced dependence of theelectrical resistivity on the square of the channel width, and by theobservation of a strong violation of the Wiedemann-Franz law. Frommagneto-hydrodynamic experiments and complementary Hall measurements, therelaxation times for momentum and thermal energy dissipating processes areextracted. Following the uncertainty principle, both are limited by thePlanckian bound of dissipation, independent of the underlying transport regime.