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We present measurements of the dynamical structure factor $S(q,\omega)$ of an interacting one-dimensional (1D) Fermi gas for small excitation energies. We use the two lowest hyperfine levels of the $^6$Li atom to form a pseudo-spin-1/2…

Atomic Physics · Physics 2018-09-12 T. L. Yang , P. Grišins , Y. T. Chang , Z. H. Zhao , C. Y. Shih , T. Giamarchi , R. G. Hulet

The virial expansion characterizes the high-temperature approach to the quantum-classical crossover in any quantum many-body system. Here, we calculate the virial coefficients up to the fifth-order of Fermi gases in 1D, 2D, and 3D, with…

Quantum Gases · Physics 2020-09-16 Y. Hou , J. E. Drut

We use the virial expansion to investigate the behavior of the two-component, attractive Fermi gas in the high-temperature limit, where the system smoothly evolves from weakly attractive fermions to weakly repulsive bosonic dimers as the…

Quantum Gases · Physics 2015-01-12 V. Ngampruetikorn , Meera M. Parish , Jesper Levinsen

The dynamic structure factor of a normal Fermi gas is investigated by using the moment method for the Boltzmann equation. We determine the spectral function at finite temperatures over the full range of crossover from the collisionless…

Quantum Gases · Physics 2010-10-05 Shohei Watabe , Tetsuro Nikuni

A dilute homogeneous 3D Fermi gas in the ground state is considered for the case of a repulsive pairwise interaction. The low-density (dilution) expansions for the kinetic and interaction energies of the system in question are calculated up…

Statistical Mechanics · Physics 2009-11-10 A. A. Shanenko

The static and dynamic structure factors of an interacting Fermi gas along the BCS-BEC crossover are calculated at momentum transfer $\hbar{\bf k}$ higher than the Fermi momentum. The spin structure factor is found to be very sensitive to…

Other Condensed Matter · Physics 2009-11-11 R. Combescot , S. Giorgini , S. Stringari

We study the dilute Fermi gas at unitarity using molecular dynamics with an effective quantum potential constructed to reproduce the quantum two-body density matrix at unitarity. Results for the equation of state, the pair correlation…

Quantum Gases · Physics 2013-05-30 Kevin Dusling , Thomas Schaefer

We compute the shear viscosity of a two dimensional Fermi gas interacting via a short range potential with scattering length $a_{2d}$ in kinetic theory. We find that kinetic theory predicts that the shear viscosity to entropy density ratio…

Quantum Gases · Physics 2013-05-30 Thomas Schaefer

We present a theoretical investigation of the dynamic density structure factor of a strongly interacting Fermi gas near a Feshbach resonance at finite temperature. The study is based on a gauge invariant linear response theory. The theory…

Quantum Gases · Physics 2018-06-29 Hao Guo , Yan He , Lianyi He

We investigate the collective excitations of a harmonically trapped two-dimensional Fermi gas from the collisionless (zero sound) to the hydrodynamic (first sound) regime. The breathing mode, which is sensitive to the equation of state, is…

Using Landau theory of Fermi liquids we calculate the dynamic response of both a polarized and unpolarized normal Fermi gas at zero temperature in the strongly interacting regime of large scattering length. We show that at small excitation…

Statistical Mechanics · Physics 2010-04-22 S. Stringari

We directly observe the hydrodynamic linear response of a unitary Fermi gas confined in a box potential and subject to a spatially periodic optical potential that is translated into the cloud at speeds ranging from subsonic to supersonic.…

Quantum Gases · Physics 2019-10-23 Lorin Baird , Xin Wang , Stetson Roof , J. E. Thomas

Following up on recent calculations, we investigate the leading- and next-to-leading order semiclassical approximation to the virial coefficients of a two-species fermion system with a contact interaction. Using the analytic result for the…

Quantum Gases · Physics 2020-08-18 Y. Hou , A. Czejdo , J. DeChant , C. R. Shill , J. E. Drut

A key quantity in strongly-interacting resonant Fermi gases is the contact $\mathcal{C}$, which characterizes numerous properties such as the momentum distribution at large momenta or the pair correlation function at short distances. The…

Quantum Gases · Physics 2018-10-02 R. Rossi , T. Ohgoe , E. Kozik , N. Prokof'ev , B. Svistunov , K. Van Houcke , F. Werner

A final-state-effects formalism suitable to analyze the high-momentum response of Fermi liquids is presented and used to study the dynamic structure function of liquid $^3$He. The theory, developed as a natural extension of the…

Statistical Mechanics · Physics 2009-11-10 F. Mazzanti , A. Polls , J. Boronat , J. Casulleras

While the 1D Bose gas appears to exhibit superfluid response under certain conditions, it fails the Landau criterion according to the elementary excitation spectrum calculated by Lieb. The apparent riddle is solved by calculating the…

Other Condensed Matter · Physics 2007-05-23 Joachim Brand , Alexander Yu. Cherny

We compute the viscosity spectral function of the dilute Fermi gas for different values of the s-wave scattering length $a$, including the unitarity limit $a\to\infty$. We perform the calculation in kinetic theory by studying the response…

Quantum Gases · Physics 2015-05-20 J. Chao , M. Braby , T. Schaefer

Based on random phase approximation (RPA), we numerically calculate dynamical structure factors of a balanced two-dimensional (2D) Fermi superfluid, and discuss their energy, momentum and interaction strength dependence in the 2D BEC-BCS…

Quantum Gases · Physics 2020-08-05 Huaisong Zhao , Xiaoxu Gao , Wen Liang , Peng Zou , Feng Yuan

The dynamic response functions of strongly interacting fermion gas in homogeneous space are investigated in a virial expansion to second order. The density response function exhibits transition from atomic to molecular response, as the…

Quantum Gases · Physics 2015-06-11 Gang Shen

Using two different numerical methods, we study the behavior of two-component Fermi gases interacting through short-range s-wave interactions in a harmonic trap. A correlated Gaussian basis-set expansion technique is used to determine the…

Other Condensed Matter · Physics 2009-11-13 J. von Stecher , Chris H. Greene , D. Blume