Linear response study of collisionless spin drag

Year: 2021

Authors: Romito Donato; Lobo Carlos; Recati Alessio

Autors Affiliation: Univ Southampton, Sch Math Sci, Southampton SO17 1BJ, Hants, England; INO CNR BEC Trento, Via Sommar 14, I-38123 Povo, TN, Italy; Univ Trento, Dipartimento Fis, Via Rodolfo Belenzani 12, I-38122 Trento, TN, Italy.

Abstract: In this work we are concerned with the understanding of the collisionless drag or entrainment between two superfluids, also called Andreev-Bashkin effect, in terms of current response functions. The drag density is shown to be proportional to the cross transverse current-current response function, playing the role of a normal component for the single-species superfluid density. We can in this way link the existence of finite entrainment with the exhaustion of the energy-weighted sum rule in the spin channel. The formalism is then used to reproduce some known results for a weakly interacting Bose-Bose mixture. We include the drag effect to determine the beyond mean-field correction on the speed of sound and on the spin dipole excitations for a homogeneous and a trapped weakly interacting gas, respectively. Finally, we show that the response to a quick dipole perturbation on one of the species induces a dipole moment on the other species which is proportional to the drag at short times.

Journal/Review: PHYSICAL REVIEW RESEARCH

Volume: 3 (2)      Pages from: 023196-1  to: 023196-12

KeyWords: Bose
DOI: 10.1103/PhysRevResearch.3.023196

Citations: 9
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