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We provide a description of the dynamic structure factor of a homogeneous unitary Fermi gas at low momentum and low frequency, based on the dissipative two-fluid hydrodynamic theory. The viscous relaxation time is estimated and is used to…

Quantum Gases · Physics 2018-02-14 Hui Hu , Peng Zou , Xia-Ji Liu

Superfluidity and superconductivity are remarkable manifestations of quantum coherence at a macroscopic scale. The dynamics of superfluids has dominated the study of these systems for decades now, but a comprehensive theoretical framework…

Quantum Gases · Physics 2011-08-19 Aurel Bulgac , Yuan-Lung , Luo , Piotr Magierski , Kenneth J. Roche , Yongle Yu

To calculate static response properties of a many body system, local density approximation (LDA) can be safely applied. But applicability of LDA is limited for the case of dynamical response functions since dynamics of the system needs to…

Quantum Gases · Physics 2015-12-01 Sudeep Kumar Ghosh

We present a pairing fluctuation theory which self-consistently incorporates finite momentum pair excitations in the context of BCS--Bose-Einstein condensation (BEC) crossover, and we apply this theory to high $T_c$ superconductors and…

Strongly Correlated Electrons · Physics 2011-09-13 Qijin Chen , Chih-Chun Chien , Yan He , K. Levin

We theoretically investigate the dynamic structure factor of a strongly interacting Fermi gas at the crossover from Bardeen-Cooper-Schrieffer superfluids to Bose-Einstein condensates, by developing an improved random phase approximation…

Quantum Gases · Physics 2017-01-06 Peng Zou , Franco Dalfovo , Rishi Sharma , Xia-Ji Liu , Hui Hu

It is quite common that several different phases exist simultaneously in a system of trapped quantum gases of ultra-cold atoms. One such example is the strongly-interacting Fermi gas with two imbalanced spin species, which has received a…

Quantum Gases · Physics 2011-05-27 L. O. Baksmaty , Hong Lu , C. J. Bolech , Han Pu

A metallic electron system near an orientational symmetry breaking Pomeranchuk instability is characterized by a ''soft'' Fermi surface with enhanced collective fluctuations. We analyze fluctuation effects in a two-dimensional electron…

Strongly Correlated Electrons · Physics 2010-12-30 Luca Dell'Anna , Walter Metzner

We study low energy collective excitations in a trapped superfluid Fermi gas, that describe slow variations of the phase of the superfluid order parameter. Well below the critical temperature the corresponding eigenfrequencies turn out to…

Statistical Mechanics · Physics 2009-10-31 M. A. Baranov , D. S. Petrov

The quasiparticle excitations and dynamical stability of an atomic Bose-Einstein condensate coupled to a quantum degenerate Fermi gas of atoms at zero temperature is studied. The Fermi gas is assumed to be either in the normal state or to…

Soft Condensed Matter · Physics 2009-11-07 C. P. Search , H. Pu , W. Zhang , P. Meystre

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

We have investigated collective breathing modes of a unitary Fermi gas in deformed harmonic traps. The ground state is studied by the Superfluid Local Density Approximation (SLDA) and small-amplitude collective modes are studied by the…

Quantum Gases · Physics 2019-11-20 Na Fei , Junchen Pei , Kai Wang , M. Kortelainen

Interacting Fermi gases with equal populations but unequal masses are investigated at zero temperature using local density approximation and the hydrodynamic theory of superfluids in the presence of harmonic trapping. We derive the…

Soft Condensed Matter · Physics 2009-11-13 G. Orso , L. P. Pitaevskii , S. Stringari

In this work, we will present a physically consistent theory to derive the governing equations of the Large Eddy Simulation (LES) framework based on first principles rather than the motivation to conduct computationally affordable…

Fluid Dynamics · Physics 2021-10-13 Max Okraschevski , Sven Hoffmann , Katharina Stichling , Rainer Koch , Hans-Joerg Bauer

Fermi gases with magnetically tunable interactions provide a clean and controllable laboratory system for modeling interparticle interactions between fermions in nature. The s-wave scattering length, which is dominant a low temperature, is…

Quantum Gases · Physics 2010-04-05 J. E. Thomas

We discuss collective excitations of a trapped dilute Fermi gas within a hydrodynamic approximation. Analytical results are derived for both high- and low-temperature limits and are applied to $^{40}$K and $^6$Li systems of current…

Condensed Matter · Physics 2009-10-31 Georg M. Bruun , Charles W. Clark

We discuss the unitary Fermi gas made of dilute and ultracold atoms with an infinite s-wave inter-atomic scattering length. First we introduce an efficient Thomas-Fermi-von Weizsacker density functional which describes accurately various…

Quantum Gases · Physics 2013-04-23 Luca Salasnich

Quantum-degenerate Fermi gases provide a remarkable opportunity to study strongly interacting fermions. In contrast to other Fermi systems, such as superconductors, neutron stars or the quark-gluon plasma, these gases have low densities and…

Superconductivity · Physics 2007-05-23 M. W. Zwierlein , J. R. Abo-Shaeer , A. Schirotzek , C. H. Schunck , W. Ketterle

We consider a few-particle system of trapped neutral fermionic atoms at ultra-low temperatures, with the attractive interaction tuned to Feshbach resonance. We calculate the energies and the spatial densities of the few-body systems using a…

Other Condensed Matter · Physics 2009-11-13 R. K. Bhaduri , M. V. N. Murthy , M. Brack

Motivated by a recent experiment [Phys. Rev. Lett. 106, 150401 (2011)] we simulate the collision between two clouds of cold Fermi gas at unitarity conditions by using an extended Thomas-Fermi density functional. At variance with the current…

Quantum Gases · Physics 2012-06-18 F. Ancilotto , L. Salasnich , F. Toigo

In this work we establish constraints on the temperature dependence of the shear viscosity $\eta$ in the superfluid phase of a dilute Fermi gas in the unitary limit. Our results are based on analyzing experiments that measure the aspect…

Quantum Gases · Physics 2021-08-18 Jiaxun Hou , Thomas Schaefer