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Title: Spectrum of spin waves in cold polarized gases

Abstract

The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.

Authors:
 [1]
  1. Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
Publication Date:
OSTI Identifier:
22617077
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Experimental and Theoretical Physics; Journal Volume: 124; Journal Issue: 2; Other Information: Copyright (c) 2017 Pleiades Publishing, Inc.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ATOMS; BOLTZMANN EQUATION; DIFFUSION; DISPERSION RELATIONS; DISPERSIONS; GASES; MAGNETIC MOMENTS; RUBIDIUM; SPECTRA; SPIN WAVES

Citation Formats

Andreeva, T. L., E-mail: phdocandreeva@yandex.ru. Spectrum of spin waves in cold polarized gases. United States: N. p., 2017. Web. doi:10.1134/S1063776117010010.
Andreeva, T. L., E-mail: phdocandreeva@yandex.ru. Spectrum of spin waves in cold polarized gases. United States. doi:10.1134/S1063776117010010.
Andreeva, T. L., E-mail: phdocandreeva@yandex.ru. Wed . "Spectrum of spin waves in cold polarized gases". United States. doi:10.1134/S1063776117010010.
@article{osti_22617077,
title = {Spectrum of spin waves in cold polarized gases},
author = {Andreeva, T. L., E-mail: phdocandreeva@yandex.ru},
abstractNote = {The spin dynamics of cold polarized gases are investigated using the Boltzmann equation. The dispersion relation for spin waves (transverse component of the magnetic moment) and the spin diffusion coefficient of the longitudinal component of the magnetic moment are calculated without using fitting parameters. The spin wave frequency and the diffusion coefficient for rubidium atoms are estimated numerically.},
doi = {10.1134/S1063776117010010},
journal = {Journal of Experimental and Theoretical Physics},
number = 2,
volume = 124,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2017},
month = {Wed Feb 15 00:00:00 EST 2017}
}
  • Boundary conditions are discussed for spin dynamics equations in dilute spin-polarized quantum gases. The bulk equations have the macroscopic hydrodynamic form even when mean free paths of the particles are large, and the main question is whether a supplementary hydrodynamic boundary condition is valid. Different boundary processes are considered including spin-conserving and non-conserving reflections, slip, formation of adsorbed surface layers, etc. The macroscopic boundary condition fails in the cases of very effective surface processes with violation of time-reversal symmetry (e.g. spin-lattice relaxation) or very high surface-induced diffusion rates. Otherwise, the surface processes are described by a simple boundary condition ormore » by {delta}-type singularities in bulk equations. The meaning of different macroscopic parameters is clarified. The formation of dense adsorbed boundary layers changes the frequency shifts and linewidths of spin-wave resonances because of effective exchanges between surface and bulk particles and strong interactions within the boundary layers. Here the broadening of resonances is explained not only by additional surface dissipation (diffusion), but also by dephasing processes originating from a renormalization of the molecular field in the boundary layers. The results explain recent experiments by the Cornell group.« less
  • Boundary conditions are derived for spin dynamics of spin-polarized quantum gases near nonmagnetic walls. We are interested mostly in boundary-induced line shifts and attenuation of spin waves, and in the possibility of having a macroscopic boundary condition for systems close to a Knudsen ballistic regime. We consider the effects caused by roughness of the wall and by surface adsorption. By a proper coordinate transformation, we reduce the problem of particle collisions with an inhomogeneous nonmagnetic wall to an equivalent problem with a specular homogeneous wall but with stochastic bulk imperfections. As a result, the boundary effects are described by somemore » additional bulklike transverse spin-diffusion coefficient inversely proportional to the angular harmonics of the correlation function of surface inhomogeneities. This leads to an effective macroscopiclike boundary condition for transverse spin dynamics responsible for the boundary effects in spin-wave resonances. The situation changes drastically at low temperatures because of an appearance of an adsorbed boundary layer which renormalizes the molecular field near the wall, and leads to additional effective spin-exchange processes. The experimental implications for helium and hydrogen systems are discussed.« less
  • Experiments on polarized fermion gases performed by trapping ultracold atoms in optical lattices allow the study of an attractive Hubbard model for which the strength of the on-site interaction is tuned by means of a Feshbach resonance. Using a well-known particle-hole transformation we discuss how results obtained for this system can be reinterpreted in the context of a doped repulsive Hubbard model. In particular, we show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state of the two-dimensional doped positive U Hubbard model. We then use the results of numerical studies of the striped state to relate the periodicitymore » of the FFLO state to the spin polarization. We also comment on the relationship of the dx2y2superconducting phase of the doped 2D repulsive Hubbard model to a d-wave spin density wave state for the attractive case.« less
  • Experiments on polarized fermion gases performed by trapping ultracold atoms in optical lattices allow the study of an attractive Hubbard model for which the strength of the on-site interaction is tuned by means of a Feshbach resonance. Using a well-known particle-hole transformation we discuss how results obtained for this system can be reinterpreted in the context of a doped repulsive Hubbard model. In particular, we show that the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state corresponds to the striped state of the two-dimensional doped positive U Hubbard model. We then use the results of numerical studies of the striped state to relate the periodicitymore » of the FFLO state to the spin polarization. We also comment on the relationship of the d{sub x{sup 2}}{sub -y{sup 2}} superconducting phase of the doped 2D repulsive Hubbard model to a d-wave spin density wave state for the attractive case.« less
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