Quantum hydrodynamics of the spinor Bose-Einstein condensate at non-zero temperatures

TL;DR

This paper develops a finite temperature hydrodynamic model for spin-1 Bose-Einstein condensates, incorporating quantum effects, Zeeman interactions, and spin dynamics, providing insights into collective excitations and sound propagation.

Contribution

It introduces a two-fluid quantum hydrodynamic model for spinor BECs at finite temperatures, including Zeeman effects and spin interactions, with analysis of collective excitations.

Findings

Spin wave unaffected by small temperature in minimal coupling model

Two sound waves influenced by spin evolution and interaction constants

Spectrum of bulk excitations analyzed in ferromagnetic phase

Abstract

Finite temperature hydrodynamic model is derived for the spin-1 ultracold bosons by the many-particle quantum hydrodynamic method. It is presented as the two fluid model of the BEC and normal fluid. The linear and quadratic Zeeman effects are included. Scalar and spin-spin like short-range interactions are considered in the first order by the interaction radius. It is also represented as the set of two nonlinear Pauli equations. The spectrum of the bulk collective excitations is considered for the ferromagnetic phase in the small temperature limit. The spin wave is not affected by the presence of the small temperature in the described minimal coupling model, where the thermal part of the spin-current of the normal fluid is neglected. The two sound waves are affected by the spin evolution in the same way as the change of spectrum of the single sound wave in BEC, where speed of sound is proportional to $g_{1}+g_{2}$ with $g_{i}$ are the interaction constants.