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We study the dynamics of counterflowing bosonic and fermionic lithium atoms. First, by tuning the interaction strength we measure the critical velocity vc of the system in the BEC-BCS crossover in the low temperature regime and we compare…

We present theoretical predictions for the equation of state of a harmonically-trapped Fermi gas in the unitary limit. Our calculations rest on a study of the equation of state of a uniform gas using three distinct perturbation schemes,…

Superconductivity · Physics 2007-05-23 Hui Hu , Xia-Ji Liu , Peter D. Drummond

We derive an expression for the superfluid density of a uniform two-component Fermi gas through the BCS-BEC crossover in terms of the thermodynamic potential in the presence of an imposed superfluid flow. Treating the pairing fluctuations…

Other Condensed Matter · Physics 2008-12-12 E. Taylor , A. Griffin , N. Fukushima , Y. Ohashi

Strongly interacting, dilute Fermi gases exhibit a scale-invariant, universal thermodynamic behaviour. This is notoriously difficult to understand theoretically because of the absence of a small interaction parameter. Here we present a…

Quantum Gases · Physics 2010-08-25 Hui Hu , Xia-Ji Liu , Peter D. Drummond

Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals…

By adopting a $T$-matrix based method within $G_0G$ approximation for the pair susceptibility, we studied the effects of pairing fluctuation on the BCS-BEC crossover in symmetric nuclear matter. The pairing fluctuation induces a pseudogap…

Nuclear Theory · Physics 2015-03-13 Xu-Guang Huang

We develop a time-dependent mean-field theory to investigate the released momentum distribution and the released energy of an ultracold Fermi gas in the BCS-BEC crossover after the scattering length has been set to zero by a fast…

Other Condensed Matter · Physics 2009-11-11 M. L. Chiofalo , S. Giorgini , M. Holland

Light scattering from a spin-polarized degenerate Fermi gas of trapped ultracold Li-6 atoms is studied. We find that the scattered light contains information which directly reflects the quantum pair correlation due to the formation of…

Statistical Mechanics · Physics 2009-10-31 Weiping Zhang , C. A. Sackett , R. G. Hulet

A number-conserving hybrid Bose-Fermi variational theory is developed and applied to investigation of the BEC-Tonks gas crossover in toroidal and long cylindrical traps of high aspect ratio, where strong many-body correlations and…

Soft Condensed Matter · Physics 2013-05-29 M. D. Girardeau , E. M. Wright

We theoretically study the thermodynamic properties of a strongly interacting Fermi gas at the crossover from a Bardeen-Cooper-Schrieffer (BCS) superfluid to a Bose-Einstein condensate (BEC), by applying a recently outlined strong-coupling…

Quantum Gases · Physics 2022-01-14 Brendan C. Mulkerin , Xing-Can Yao , Yoji Ohashi , Xia-Ji Liu , Hui Hu

The functional renormalisation group is used for the BCS-BEC crossover in gases of ultracold fermionic atoms. In a simple truncation, we see how universality and an effective theory with composite bosonic di-atom states emerge. We obtain a…

Superconductivity · Physics 2009-11-13 S. Diehl , H. Gies , J. M. Pawlowski , C. Wetterich

We study the superfluid critical temperature in a two-band attractive Fermi system with strong pairing fluctuations associated with both interband and intraband couplings. We focus specifically on a configuration where the intraband…

Quantum Gases · Physics 2019-06-05 Hiroyuki Tajima , Yuriy Yerin , Andrea Perali , Pierbiagio Pieri

Ultracold atomic gases are a powerful tool to experimentally study strongly correlated quantum many-body systems. In particular, ultracold Fermi gases with tunable interactions have allowed to realize the famous BEC-BCS crossover from a…

We study the superfluid state of atomic Fermi gases using a BCS-BEC crossover theory. Our approach emphasizes non-condensed fermion pairs which strongly hybridize with their (Feshbach-induced) molecular boson counterparts. These pairs lead…

Soft Condensed Matter · Physics 2011-09-13 Jelena Stajic , J. N. Milstein , Qijin Chen , M. L. Chiofalo , M. J. Holland , K. Levin

We investigate the single-particle properties at T=0 of a trapped superfluid gas of Fermi atoms with a Feshbach resonance. A tunable pairing interaction associated with the Feshbach resonance leads to the BCS-BEC crossover, where the…

Other Condensed Matter · Physics 2009-11-10 Y. Ohashi , A. Griffin

We study Gaussian fluctuations of the zero-temperature attractive Fermi gas in the 2D BCS-BEC crossover showing that they are crucial to get a reliable equation of state in the BEC regime of composite bosons, bound states of fermionic…

Quantum Gases · Physics 2015-01-27 L. Salasnich , F. Toigo

In the last 25 years, much progress has been made producing and controlling Bose-Einstein condensates (BECs) and degenerate Fermi gases. The advances in trapping, cooling and tuning the interparticle interactions in these cold atom systems…

Quantum Gases · Physics 2021-02-23 Lucas Madeira , Vanderlei S. Bagnato

We contrast {\it four} distinct versions of the BCS-Bose statistical crossover theory according to the form assumed for the electron-number equation that accompanies the BCS gap equation. The four versions correspond to explicitly…

Superconductivity · Physics 2009-11-11 S. K. Adhikari , M. de Llano , F. J. Sevilla , M. A. Solis , J. J. Valencia

A Fermi liquid with weak attractive interaction undergoes a BCS transition to a superconductor with reducing temperature. With increasing interaction strength, the thermal transition is progressively modified as the high temperature…

Strongly Correlated Electrons · Physics 2011-05-06 Sabyasachi Tarat , Pinaki Majumdar

We present measurements of the temperature-dependent momentum distribution of a trapped Fermi gas consisting of $^{40}$K in the BCS-BEC crossover regime. Accompanying theoretical results based upon a simple mean-field ground state are…

Strongly Correlated Electrons · Physics 2011-09-13 Qijin Chen , C. A. Regal , D. S. Jin , K. Levin