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Title
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Collective excitations of superfluid Fermi gases near the transition temperature
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Author
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Abstract
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| Studying the collective pairing phenomena in a two-component Fermi gas, we predict the appearance near the transition temperature T-c of a well-resolved collective mode of quadratic dispersion. The mode is visible both above and below T-c in the system's response to a driving pairing field. When approaching T-c from below, the phononic and pair-breaking branches, characteristic of the zero temperature behavior, reduce to a relatively low energy-momentum region. Elsewhere they are replaced by the quadratically dispersed pairing resonance, which thus acts as a precursor of the phase transition. In the strong-coupling and Bose-Einstein condensate regime, this mode is a weakly damped propagating mode associated with a Lorentzian resonance. Conversely, in the BCS limit it is a relaxation mode of pure imaginary eigenenergy. At large momenta, the resonance disappears when it is reabsorbed by the lower edge of the pairing continuum. At intermediate temperatures between 0 and Tc we unify the newly found collective phenomena near T-c with the phononic and pair-breaking branches predicted from previous studies, and we exhaustively classify the roots of the analytically continued dispersion equation, and show that they provided a very good summary of the pair spectral functions. |
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Language
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English
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Source (journal)
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Physical review A
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Publication
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2021
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DOI
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10.1103/PHYSREVA.103.043336
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Volume/pages
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103
:4
(2021)
, 20 p.
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Article Reference
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043336
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ISI
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000646169800007
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Medium
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E-only publicatie
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Full text (Publisher's DOI)
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Full text (open access)
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