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The nature of the normal state of an ultracold Fermi gas in the BCS-BEC crossover regime is an intriguing and controversial topic. While the many-body ground state remains a condensate of paired fermions, the normal state must evolve from a…

Quantum Gases · Physics 2015-03-03 Yoav Sagi , Tara E. Drake , Rabin Paudel , Roman Chapurin , Deborah S. Jin

Ultracold Fermi gases subject to tight transverse confinement offer a highly controllable setting to study the two-dimensional (2D) BCS to Berezinskii-Kosterlitz-Thouless superfluid crossover. Achieving the 2D regime requires confining…

Quantum Gases · Physics 2016-01-20 P. Dyke , K. Fenech , T. Peppler , M. G. Lingham , S. Hoinka , W. Zhang , B. Mulkerin , H. Hu , X. -J. Liu , C. J. Vale

We obtain the phase diagram of spin-imbalanced interacting Fermi gases from measurements of density profiles of $^6$Li atoms in a harmonic trap. These results agree with, and extend, previous experimental measurements. Measurements of the…

Atomic Physics · Physics 2015-12-16 Ben A. Olsen , Melissa C. Revelle , Jacob A. Fry , Daniel E. Sheehy , Randall G. Hulet

We investigate pairing in a strongly interacting two-component Fermi gas with positive scattering length. In this regime, pairing occurs at temperatures above the superfluid critical temperature; unbound fermions and pairs coexist in…

Ultra-cold atom experiments offer the unique opportunity to study mixing of different types of superfluid states. Our interest is in superfluid mixtures comprising particles with different statistics- Bose and Fermi. Such scenarios occur…

Quantum Gases · Physics 2015-03-18 B. Ramachandhran , S. G. Bhongale , H. Pu

The superfluidity and pairing phenomena in ultracold atomic Fermi gases have been of great interest in recent years, with multiple tunable parameters. Here we study the BCS-BEC crossover behavior of balanced two-component Fermi gases in a…

Quantum Gases · Physics 2020-05-20 Jibiao Wang , Leifeng Zhang , Yi Yu , Chaohong Lee , Qijin Chen

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 two-component gas of fermionic atoms confined to a quasi-two-dimensional (quasi-2D) geometry by a harmonic trapping potential in the transverse direction. We construct a mean field theory of the BCS-BEC crossover at zero…

Quantum Gases · Physics 2014-03-04 Andrea M. Fischer , Meera M. Parish

We discuss the BCS-BEC crossover in a degenerate Fermi gas of two hyperfine states interacting close to a Feshbach resonance. This system has quasi-molecular Bosons associated with a Feshbach resonance, and this kinds of coupled…

Soft Condensed Matter · Physics 2016-08-31 Y. Ohashi , A. Griffin

We present an overview of our recent measurements on the crossover from a Bose-Einstein condensate of molecules to a Bardeen-Cooper-Schrieffer superfluid. The experiments are performed on a two-component spin-mixture of $^6$Li atoms, where…

Other Condensed Matter · Physics 2009-11-10 M. Bartenstein , A. Altmeyer , S. Riedl , S. Jochim , R. Geursen , C. Chin , J. Hecker Denschlag , R. Grimm

We present an experimental study of the time of flight properties of a gas of ultra-cold fermions in the BEC-BCS crossover. Since interactions can be tuned by changing the value of the magnetic field, we are able to probe both non…

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

We theoretically investigate excitation properties in the pseudogap regime of a trapped Fermi gas. Using a combined $T$-matrix theory with the local density approximation, we calculate strong-coupling corrections to single-particle local…

Quantum Gases · Physics 2015-05-28 Shunji Tsuchiya , Ryota Watanabe , Yoji Ohashi

We investigate the dimensional crossover from three to two dimensions in an ultracold Fermi gas across the whole BCS-BEC crossover. Of particular interest is the strongly interacting regime as strong correlations are more pronounced in…

Quantum Gases · Physics 2021-03-23 Bruno M. Faigle-Cedzich , Jan M. Pawlowski , Christof Wetterich

We present a theoretical analysis of phase separations between two repulsively interacting components in an ultracold fermionic gas, occurring at the dimensional crossover in a harmonic trap with varying aspect ratios. A tailored kinetic…

We have measured the heat capacity of an optically-trapped, strongly-interacting Fermi gas of atoms. A precise input of energy to the gas is followed by single-parameter thermometry, which determines the empirical temperature parameter…

Other Condensed Matter · Physics 2011-09-13 J. Kinast , A. Turlapov , J. E. Thomas , Qijin Chen , Jelena Stajic , K. Levin

We model the one-dimension (1D) to three-dimension (3D) crossover in a cylindrically trapped Fermi gas with attractive interactions and spin-imbalance. We calculate the mean-field phase diagram, and study the relative stability of exotic…

Quantum Gases · Physics 2016-12-22 Shovan Dutta , Erich J. Mueller

Ultracold atom gases provide model systems in which many-body quantum physics phenomena can be studied. Recent experiments on Fermi gases have realized a phase transition to a Fermi superfluid state with strong interparticle interactions.…

Other Condensed Matter · Physics 2008-09-04 J. T. Stewart , J. P. Gaebler , D. S. Jin

Atomic Fermi gases have been an ideal platform for simulating conventional and engineering exotic physical systems owing to their multiple tunable control parameters. Here we investigate the effects of mixed dimensionality on the superfluid…

Quantum Gases · Physics 2017-10-12 Leifeng Zhang , Yanming Che , Jibiao Wang , Qijin Chen

We present a theory for a superfluid Fermi gas near the BCS-BEC crossover, including pairing fluctuation contributions to the free energy similar to that considered by Nozieres and Schmitt-Rink for the normal phase. In the strong coupling…

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