Formation of an electron-phonon bi-fluid in bulk antimony

TL;DR

This paper reports the discovery of a two-component electron-phonon bi-fluid in bulk antimony, where momentum-conserving collisions dominate transport, leading to unique thermal and electrical behaviors at low temperatures.

Contribution

It provides experimental evidence for a hydrodynamic electron-phonon bi-fluid in bulk antimony, a phenomenon rarely observed in three-dimensional solids.

Findings

Electron scattering dominates lattice thermal conductivity down to 0.1 K.

Electrical resistivity shows a quadratic temperature dependence below 15 K.

Electron and phonon scattering times exhibit similar temperature dependence.

Abstract

The flow of charge and entropy in solids usually depends on collisions decaying quasiparticle momentum. Hydrodynamic corrections can emerge, however, if most collisions among quasiparticles conserve momentum and the mean-free-path approaches the sample dimensions. Here, through a study of electrical and thermal transport in antimony (Sb) crystals of various sizes, we document the emergence of a two-component fluid of electrons and phonons. Lattice thermal conductivity is dominated by electron scattering down to 0.1 K and displays prominent quantum oscillations. The Dingle mobility does not vary despite an order-of-magnitude change in transport mobility. The Bloch-Gr\"uneisen behavior of electrical resistivity is suddenly aborted below 15 K and replaced by a quadratic temperature dependence. At Kelvin temperature range, the phonon scattering time and the electron-electron scattering time display a similar amplitude and temperature dependence. Taken together, the results draw a consistent picture of a bi-fluid where frequent momentum-conserving collisions between electrons and phonons dominate the transport properties.