Lecturer: Dr. Asaf Hamo

Abstract:  Hydrodynamicelectron flow is a unique signature of strong electron interactions in amaterial. This effect has been observed in 2D materials, but observations inbulk materials are intriguing as high-carrier density should screen theinteractions. In this work, we study hydrodynamic flow in the semimetal WTe2 togain insight into the microscopic origin of its electron interactions.

We image the spatial profile of the electric current by using anitrogen-vacancy scanning tip. Using coherent quantum sensing, we obtainmagnetic field resolution of ~10nT and spatial resolution of ~100nm. Thecurrent pattern we observe differs substantially from the flat profile of anormal metal, and indicates correlated flow through the semi-metal. The patternalso shows non-monotonic temperature dependence, with hydrodynamic effectspeaking at ~20 K.

We compare our results to a model which combines ab initio electron scatteringrates and the electronic Boltzmann transport equation.
The model shows quantitative agreement with our measurement, allowing us toextract the strength of electron-electron interactions in our material.Furthermore, we conclude that electron interactions are phonon-mediated. Thisresult opens a path for hydrodynamic flow and strong interactions in a varietyof new materials.