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Miscibility in a degenerate fermionic mixture induced by linear coupling

Miscibility in a degenerate fermionic mixture induced by linear coupling We consider a one-dimensional mean-field-hydrodynamic model of a two-component degenerate Fermi gas in an external trap, each component representing a spin state of the same atom. We demonstrate that the interconversion between them (linear coupling), imposed by a resonant electromagnetic wave, transforms the immiscible binary gas into a miscible state, if the coupling constant, κ , exceeds a critical value, κ cr . The effect is predicted in a variational approximation, and confirmed by numerical solutions. Unlike the recently studied model of a binary Bose-Einsten condensate with the linear coupling, the components in the immiscible phase of the binary fermion mixture never fill two separated domains with a wall between them, but rather form antilocked ( π -phase-shifted) density waves. Another difference from the bosonic mixture is spontaneous breaking of symmetry between the two components in terms of the numbers of atoms in them, N 1 and N 2 . The latter effect is characterized by the parameter ν ≡ ( N 1 − N 2 ) ∕ ( N 1 + N 2 ) (only N 1 + N 2 is a conserved quantity), the onset of miscibility at κ ⩾ κ cr meaning a transition to ν ≡ 0 . At κ < κ cr , ν features damped oscillations as a function of κ . We also briefly consider an asymmetric model, with a chemical-potential difference between the two components. The relation between the imbalance in the spin population, induced by the linear coupling, and the developing spatial structure resembles the known Larkin-Ovchinnikov-Fulde-Ferrell states in the Fermi mixture. Dynamical states, when κ is suddenly switched from zero to a value exceeding κ cr , are considered too. In the latter case, the system features oscillatory relaxation to the mixed state. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Physical Review A American Physical Society (APS)

Miscibility in a degenerate fermionic mixture induced by linear coupling

Physical Review A , Volume 74 (5) – Nov 1, 2006
8 pages

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Publisher
American Physical Society (APS)
Copyright
Copyright © 2006 The American Physical Society
ISSN
1094-1622
DOI
10.1103/PhysRevA.74.053620
Publisher site
See Article on Publisher Site

Abstract

We consider a one-dimensional mean-field-hydrodynamic model of a two-component degenerate Fermi gas in an external trap, each component representing a spin state of the same atom. We demonstrate that the interconversion between them (linear coupling), imposed by a resonant electromagnetic wave, transforms the immiscible binary gas into a miscible state, if the coupling constant, κ , exceeds a critical value, κ cr . The effect is predicted in a variational approximation, and confirmed by numerical solutions. Unlike the recently studied model of a binary Bose-Einsten condensate with the linear coupling, the components in the immiscible phase of the binary fermion mixture never fill two separated domains with a wall between them, but rather form antilocked ( π -phase-shifted) density waves. Another difference from the bosonic mixture is spontaneous breaking of symmetry between the two components in terms of the numbers of atoms in them, N 1 and N 2 . The latter effect is characterized by the parameter ν ≡ ( N 1 − N 2 ) ∕ ( N 1 + N 2 ) (only N 1 + N 2 is a conserved quantity), the onset of miscibility at κ ⩾ κ cr meaning a transition to ν ≡ 0 . At κ < κ cr , ν features damped oscillations as a function of κ . We also briefly consider an asymmetric model, with a chemical-potential difference between the two components. The relation between the imbalance in the spin population, induced by the linear coupling, and the developing spatial structure resembles the known Larkin-Ovchinnikov-Fulde-Ferrell states in the Fermi mixture. Dynamical states, when κ is suddenly switched from zero to a value exceeding κ cr , are considered too. In the latter case, the system features oscillatory relaxation to the mixed state.

Journal

Physical Review AAmerican Physical Society (APS)

Published: Nov 1, 2006

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