Abstract
In stark contrast to ordinary metals, in materials in which electrons strongly interact with each other or with phonons, electron transport is thought to resemble the flow of viscous fluids. Despite their differences, it is predicted that transport in both conventional and correlated materials is fundamentally limited by the uncertainty principle applied to energy dissipation. Here we report the observation of experimental signatures of hydrodynamic electron flow in the Weyl semimetal tungsten diphosphide. Using thermal and magneto-electric transport experiments, we find indications of the transition from a conventional metallic state at higher temperatures to a hydrodynamic electron fluid below 20 K. The hydrodynamic regime is characterized by a viscosity-induced dependence of the electrical resistivity on the sample width and by a strong violation of the Wiedemann–Franz law. Following the uncertainty principle, both electrical and thermal transport are bound by the quantum indeterminacy, independent of the underlying transport regime.
Highlights
In stark contrast to ordinary metals, in materials in which electrons strongly interact with each other or with phonons, electron transport is thought to resemble the flow of viscous fluids
Electrical and thermal transport are related via the Wiedemann–Franz law, which states that the product of the electrical resistivity ρ and the thermal conductivity κ, divided by the temperature T is a constant L = ρκ/T, yielding the Sommerfeld value L0 = 2.44 × 10−8 W Ω K−2. ρ and κ are intrinsic material properties and independent of the size and geometry of the conducting bulk
In contrast to the free-electron gas, the energy dissipation in a hydrodynamic electron fluid is dominated by momentumconserving electron–electron scattering or small-angle electron–phonon scattering[10]
Summary
In stark contrast to ordinary metals, in materials in which electrons strongly interact with each other or with phonons, electron transport is thought to resemble the flow of viscous fluids. Despite their differences, it is predicted that transport in both conventional and correlated materials is fundamentally limited by the uncertainty principle applied to energy dissipation. Its basis is that the carriers move unimpededly until they scatter with phonons or defects Such collisions usually relax both the momentum and the energy currents, and impose a resistance to charge and heat flow alike. A strong violation of the Wiedemann–Franz law is predicted[3,4,5,14]
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