Event Details

Electron hydrodynamics in graphene

Abstract: When the electron-phonon and electron-impurity scattering are weak, but electron-electron collisions are sufficiently frequent to provide local equilibrium, electrons can behave as a viscous liquid and exhibit hydrodynamic phenomena similar to classical liquids. As a result, anomalous (negative) voltage drops near current injection contacts can be observed in transport experiments. These are related to the viscosity of electrons and their measurement allows one to extract such parameter, which turns out to be three orders of magnitudes that of honey. Similar effects can be observed in constrictions or in the presence of a magnetic field, where a new viscosity coefficient (the “Hall viscosity”) appears.

In such hydrodynamic regime of transport, well-known relations between coefficients can be largely violated. This is the case of the Wiedemann-Franz law, which connects the electronic thermal conductivity to the electrical conductivity of disordered metals. Large deviations from the standard form of the law are expected, due to the fact that electron-electron interactions affect the two conductivities in radically different ways, with their ratio being reduced by a large factor. We show how this temperature-dependent reduction gives rise to striking thermoelectric phenomena. These include a strong increase in thermoelectric efficiency, qualitative changes in the steady state temperature profile, and an anomalously large Thomson effect. These effects should be observable in graphene.