Project Summary: Hydrodynamic Transport in Coupled Electron-Phonon Fluids
Fazel Tafti, Boston College, Physics Department

A triumph of quantum physics, as it was being developed during the 20th century, was to explain the electronic transport in metals and justify the well-known Ohm's law. The theory of metallic conduction is based on the assumption that electrons behave as a dilute gas of charged particles that rarely come into contact. This theory has been successfully applied to nearly all conventional metals. However, recent works on unconventional metals such as graphene and delafossite systems have revealed evidence of a different kind of electronic behavior - one in which the electrons behave as interacting particles of a fluid, rather than independent gas molecules. This project, supported by the DOE Physical Behavior of Materials program, seeks to design three-dimensional materials that exhibit such fluid-like or hydrodynamic behavior. The central hypothesis is to design materials that accommodate cooperative interactions between the lattice vibrational modes (phonons) and conduction electrons. Under specific conditions, related to the phonon-electron and phonon-phonon scattering, a metallic specimen could transition from the conventional gas-like regime to the new fluid-like (hydrodynamic) regime. Accessing the electron hydrodynamic limit will unlock new potentials for electronic technologies, including extremely high conductivity, non-local and non-linear electronic transport, and novel magneto-electric effects useful for next-generation quantum devices. The research performed at Boston College will involve designing and growing crystals of such materials, as well as performing electronic transport experiments on mesoscopic devices fabricated from the proposed materials.