Electrical and Thermal Transport at the Planckian Bound of Dissipation in the Hydrodynamic Electron Fluid of WP2

TL;DR

This study demonstrates hydrodynamic electron flow in WP2, revealing that both electrical and thermal dissipation are limited by the Planckian bound, with transport transitioning from metallic to fluid-like behavior below 20 K.

Contribution

It provides experimental evidence of hydrodynamic electron flow in a Weyl semimetal and shows dissipation limits set by the Planckian bound across different transport regimes.

Findings

Hydrodynamic electron flow observed below 20 K in WP2.

Electrical resistivity depends on channel width squared in the hydrodynamic regime.

Dissipation times are limited by the Planckian bound, regardless of transport regime.

Abstract

Materials with strongly-correlated electrons exhibit interesting phenomena such as metal-insulator transitions and high-temperature superconductivity. In stark contrast to ordinary metals, electron transport in these materials 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 discover hydrodynamic electron flow in the Weyl-semimetal tungsten phosphide (WP2). Using thermal and magneto-electric transport experiments, we observe 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 square of the channel width, and by the observation of a strong violation of the Wiedemann-Franz law. From magneto-hydrodynamic experiments and complementary Hall measurements, the relaxation times for momentum and thermal energy dissipating processes are extracted. Following the uncertainty principle, both are limited by the Planckian bound of dissipation, independent of the underlying transport regime.