Propagation of first and second sound in a two-dimensional Fermi superfluid
Year: 2021
Authors: Tononi A.; Cappellaro A.; Bighin G.; Salasnich L.
Autors Affiliation: Univ Padua, Dipartimento Fis & Astron Galileo Galilei, Via Marzolo 8, I-35131 Padua, Italy; IST Austria Inst Sci & Technol Austria, Campus 1, A-3400 Klosterneuburg, Austria; Heidelberg Univ, Inst Theoret Phys, Philosophenweg 19, D-69120 Heidelberg, Germany; Consiglio Nazl Ric CNR, Ist Nazl Ott INO, Via Nello Carrara 1, I-50125 Sesto Fiorentino, Italy; Ist Nazl Fis Nucl INFN, Sez Padova, Via Marzolo 8, I-35131 Padua, Italy.
Abstract: Sound propagation is a macroscopic manifestation of the interplay between the equilibrium thermodynamics and the dynamical transport properties of fluids. Here, for a two-dimensional system of ultracold fermions, we calculate the first and second sound velocities across the whole BCS-BEC crossover, and we analyze the system response to an external perturbation. In the low-temperature regime we reproduce the recent measurements [Phys. Rev. Lett. 124, 240403 (2020)PRLTAO0031-900710.1103/PhysRevLett.124.240403] of the first sound velocity, which, due to the decoupling of density and entropy fluctuations, is the sole mode excited by a density probe. Conversely, a heat perturbation excites only the second sound, which, being sensitive to the superfluid depletion, vanishes in the deep BCS regime and jumps discontinuously to zero at the Berezinskii-Kosterlitz-Thouless superfluid transition. A mixing between the modes occurs only in the finite-temperature BEC regime, where our theory converges to the purely bosonic results.
Journal/Review: PHYSICAL REVIEW A
Volume: 103 (6) Pages from: L061303-1 to: L061303-6
KeyWords: LIQUID-HELIUM; GAS; BCSDOI: 10.1103/PhysRevA.103.L061303Citations: 8data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-10-27References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here