@article{9606,
  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)] 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.},
  author       = {Tononi, A. and Cappellaro, Alberto and Bighin, Giacomo and Salasnich, L.},
  issn         = {24699934},
  journal      = {Physical Review A},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Propagation of first and second sound in a two-dimensional Fermi superfluid}},
  doi          = {10.1103/PhysRevA.103.L061303},
  volume       = {103},
  year         = {2021},
}

@article{8319,
  abstract     = {We demonstrate that releasing atoms into free space from an optical lattice does not deteriorate cavity-generated spin squeezing for metrological purposes. In this work, an ensemble of 500000 spin-squeezed atoms in a high-finesse optical cavity with near-uniform atom-cavity coupling is prepared, released into free space, recaptured in the cavity, and probed. Up to ∼10 dB of metrologically relevant squeezing is retrieved for 700μs free-fall times, and decaying levels of squeezing are realized for up to 3 ms free-fall times. The degradation of squeezing results from loss of atom-cavity coupling homogeneity between the initial squeezed state generation and final collective state readout. A theoretical model is developed to quantify this degradation and this model is experimentally validated.},
  author       = {Wu, Yunfan and Krishnakumar, Rajiv and Martínez-Rincón, Julián and Malia, Benjamin K. and Hosten, Onur and Kasevich, Mark A.},
  issn         = {24699934},
  journal      = {Physical Review A},
  number       = {1},
  publisher    = {American Physical Society},
  title        = {{Retrieval of cavity-generated atomic spin squeezing after free-space release}},
  doi          = {10.1103/PhysRevA.102.012224},
  volume       = {102},
  year         = {2020},
}

@article{6632,
  abstract     = {We consider a two-component Bose gas in two dimensions at a low temperature with short-range repulsive interaction. In the coexistence phase where both components are superfluid, interspecies interactions induce a nondissipative drag between the two superfluid flows (Andreev-Bashkin effect). We show that this behavior leads to a modification of the usual Berezinskii-Kosterlitz-Thouless (BKT) transition in two dimensions. We extend the renormalization of the superfluid densities at finite temperature using the renormalization-group approach and find that the vortices of one component have a large influence on the superfluid properties of the other, mediated  by  the  nondissipative  drag.  The  extended  BKT  flow  equations  indicate  that  the  occurrence  of  the vortex unbinding transition in one of the components can induce the breakdown of superfluidity also in the other, leading to a locking phenomenon for the critical temperatures of the two gases.},
  author       = {Karle, Volker and Defenu, Nicolò and Enss, Tilman},
  issn         = {24699934},
  journal      = {Physical Review A},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Coupled superfluidity of binary Bose mixtures in two dimensions}},
  doi          = {10.1103/PhysRevA.99.063627},
  volume       = {99},
  year         = {2019},
}