High-Frequency Sound in a Unitary Fermi Gas
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2020-04-17
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en
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6
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Physical Review Letters, Volume 124, issue 15
Abstract
We present an experimental and theoretical study of the phonon mode in a unitary Fermi gas. Using two-photon Bragg spectroscopy, we measure excitation spectra at a momentum of approximately half the Fermi momentum, both above and below the superfluid critical temperature T_{c}. Below T_{c}, the dominant excitation is the Bogoliubov-Anderson (BA) phonon mode, driven by gradients in the phase of the superfluid order parameter. The temperature dependence of the BA phonon is consistent with a theoretical model based on the quasiparticle random phase approximation in which the dominant damping mechanism is via collisions with thermally excited quasiparticles. As the temperature is increased above T_{c}, the phonon evolves into a strongly damped collisional mode, accompanied by an abrupt increase in spectral width. Our study reveals strong similarities between sound propagation in the unitary Fermi gas and bosonic liquid helium.Description
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Kuhn, C C N, Hoinka, S, Herrera, I, Dyke, P, Kinnunen, J J, Bruun, G M & Vale, C J 2020, ' High-Frequency Sound in a Unitary Fermi Gas ', Physical Review Letters, vol. 124, no. 15, 150401 . https://doi.org/10.1103/PhysRevLett.124.150401