Spin Drag in a Bose Gas

TL;DR

This paper reports the first observation of spin drag in a bosonic gas, demonstrating enhanced spin relaxation at low temperatures due to Bose stimulation, and highlights the potential for bosonic transport in atomtronics.

Contribution

It provides the first experimental observation of spin drag in a bosonic system and confirms theoretical predictions about Bose stimulation effects at low temperatures.

Findings

Spin drag observed in ultra-cold bosonic atoms.

Spin drag is enhanced at low temperatures due to Bose stimulation.

Potential for bosonic transport to impact atomtronics development.

Abstract

It is well known that the charge current in a conductor is proportional to the applied electric field. This famous relation, known as Ohm's law, is the result of relaxation of the current due to charge carriers undergoing collisions, predominantly with impurities and lattice vibrations in the material. The field of spintronics, where the spin of the electron is manipulated rather than its charge, has recently also led to interest in spin currents. Contrary to charge currents, these spin currents can be subject to strong relaxation due to collisions between different spin species, a phenomenon known as spin drag. This effect has been observed for electrons in semi-conductors\cite{Weber} and for cold fermionic atoms, where in both cases it is reduced at low temperatures due to the fermionic nature of the particles. Here, we perform a transport experiment using ultra-cold bosonic atoms and observe spin drag for bosons for the first time. By lowering the temperature we find that spin drag for bosons is enhanced in the quantum regime due to Bose stimulation, which is in agreement with recent theoretical predictions. Our work on bosonic transport shows that this field may be as rich as transport in solid-state physics and may lead to the development of advanced devices in atomtronics.