Many-particle Quantum Hydrodynamics of Spin-1 Bose-Einstein Condensates

TL;DR

This paper develops a quantum hydrodynamic model for spin-1 Bose-Einstein condensates, revealing new effects of spin self-interactions on collective excitations and predicting anisotropic spin wave instability.

Contribution

It introduces a novel QHD-based model for spin-1 BECs, deriving modified fluid and spin equations including spin torque effects and analyzing their impact on collective excitations.

Findings

Modified dispersion spectrum with spin self-interaction contributions

Prediction of anisotropic spin wave instability

Influence of external magnetic field and spin-spin interactions

Abstract

We develop a novel model of the magnetized spin-1 Bose-Einstein condensate (BEC) of neutral atoms, using the method of many-particle quantum hydrodynamic (QHD) and propose an original derivation of the system of continual equations. We consider bosons with a spin-spin interaction and a short range interaction in the first order in the interaction radius, on the of basis of the self-consistent field approximation of the QHD equations. We demonstrate that the dynamics of the fluid velocity and magnetization is determined by a nontrivial modification of the Euler and Landau-Lifshitz equation, and show that a nontrivial modification of the spin density evolution equation contains the spin torque effect that arises from the self-interactions between spins of the bosons. The properties of the dispersion spectrum of collective excitations are described. We obtain the new contribution of the self-interaction of spins in the spin wave spectrum together with the influence of an external magnetic field and spin-spin interactions between polarized particles. The anisotropic spin wave instability is predicted.