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The strongly attractive Fermi gas in the BCS-BEC crossover is efficiently described in terms of coupled fermions and fermion pairs, or molecules. We compute the spectral functions of both fermions and pairs in the normal state near the…

Quantum Gases · Physics 2024-03-01 Tilman Enss

The superfluid density is a fundamental quantity describing the response to a rotation as well as in two-fluid collisional hydrodynamics. We present extensive calculations of the superfluid density \rho_s in the BCS-BEC crossover regime of…

Materials Science · Physics 2012-05-10 N. Fukushima , Y. Ohashi , E. Taylor , A. Griffin

This article is written as a Lecture given in the 2006 Varenna Summer School on "Ultracold Fermi Gases". Here we present a review of BCS--Bose Einstein condensation (BEC) crossover theory with emphasis on finite temperature effects. We…

Strongly Correlated Electrons · Physics 2011-09-13 K. Levin , Qijin Chen

We investigate the finite-temperature superfluid behavior of ultracold atomic Fermi gases in quasi-two-dimensional Lieb lattices with a short-range attractive interaction, using a pairing fluctuation theory within the BCS-BEC crossover…

Quantum Gases · Physics 2024-01-09 Hao Deng , Lin Sun , Chuping Li , Yuxuan Wu , Junru Wu , Qijin Chen

We provide a comprehensive theoretical study of the radio-frequency (rf) spectra of a two-component Fermi gas with balanced populations in the normal region of the temperature-vs-coupling phase diagram. In particular, rf spectra are…

Quantum Gases · Physics 2024-01-24 L. Pisani , M. Pini , P. Pieri , G. Calvanese Strinati

We review the study of the superfluid phase transition in a system of fermions whose interaction can be tuned continuously along the crossover from Bardeen-Cooper-Schrieffer (BCS) superconducting phase to a Bose-Einstein condensate (BEC),…

Quantum Gases · Physics 2021-05-06 Luca Dell'Anna , Stefano Grava

We theoretically investigate the isothermal compressibility $\kappa_{T}$ in the normal state of an ultracold Fermi gas. Including pairing fluctuations, as well as preformed-pair formations, within the framework of the self-consistent…

Quantum Gases · Physics 2022-09-09 Daichi Kagamihara , Ryohei Sato , Koki Manabe , Hiroyuki Tajima , Yoji Ohashi

We experimentally investigate the first-order correlation function of a trapped Fermi gas in the two-dimensional BEC-BCS crossover. We observe a transition to a low-temperature superfluid phase with algebraically decaying correlations. We…

Quantum Gases · Physics 2015-07-03 P. A. Murthy , I. Boettcher , L. Bayha , M. Holzmann , D. Kedar , M. Neidig , M. G. Ries , A. N. Wenz , G. Zürn , S. Jochim

The theoretical description of the critical temperature Tc of a Fermi superfluid dates back to the work by Gor'kov and Melik-Barkhudarov (GMB), who addressed it for a weakly-coupled (dilute) superfluid in the BCS (weak-coupling) limit of…

Superconductivity · Physics 2018-02-07 L. Pisani , A. Perali , P. Pieri , G. Calvanese Strinati

We investigate the effects of topological order on the transition temperature, $T_c$, and response functions in fermionic superfluids with Rashba spin-orbit coupling and a transverse Zeeman field in three dimensions. Our calculations,…

Quantum Gases · Physics 2016-05-10 Brandon M. Anderson , Chien-Te Wu , Rufus Boyack , K. Levin

We investigate a mix-dimensional Fermi-Fermi mixture in which one species is confined in two-dimensional(2D) space while the other is free in three-dimensional space(3D). We determine the superfluid transition temperature $T_{c}$ for the…

Superconductivity · Physics 2015-05-27 Xiaosen Yang , Beibing Huang , Shaolong Wan

We observe many-body pairing in a two-dimensional gas of ultracold fermionic atoms at temperatures far above the critical temperature for superfluidity. For this, we use spatially resolved radio-frequency spectroscopy to measure pairing…

Fermionic superfluidity requires the formation of pairs. The actual size of these fermion pairs varies by orders of magnitude from the femtometer scale in neutron stars and nuclei to the micrometer range in conventional superconductors.…

Superconductivity · Physics 2008-08-14 Christian H. Schunck , Yong-il Shin , Andre Schirotzek , Wolfgang Ketterle

This paper gives a survey of a diagrammatic approach for fermionic pairing fluctuations, which are relevant to the BCS-BEC crossover realized with ultracold Fermi gases. Emphasis will be given to the physical intuition about the relevant…

Quantum Gases · Physics 2010-11-29 G. C. Strinati

The strongly-correlated regime of the BCS-BEC crossover can be realized by diluting a system of two-component fermions with a short-range attractive interaction. We investigate this system via a novel continuous-space-time diagrammatic…

Strongly Correlated Electrons · Physics 2009-11-13 Evgeni Burovski , Evgeny Kozik , Nikolay Prokof'ev , Boris Svistunov , Matthias Troyer

We study the coherence properties of a trapped two-component gas of fermionic atoms below the BCS critical temperature. We propose an optical method to investigate the Cooper-pair coherence across different regions of the superfluid.…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 Gh. -S. Paraoanu , M. Rodriguez , P. Torma

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 propose a simple bose-fermi model in two dimensions, with a coupling that converts pairs of opposite spin fermions into localized bosons and vice versa. We show that tracing out one of the degrees, either the bosons or fermions,…

Superconductivity · Physics 2020-10-23 Maciej M. Maśka , Nandini Trivedi

We determine the size of the critical region of the superfluid transition in the BCS-BEC crossover of a three-dimensional fermion gas, using a renormalization-group approach to a bosonic theory of pairing fluctuations. For the unitary Fermi…

Quantum Gases · Physics 2016-03-08 T. Debelhoir , N. Dupuis

We consider the two-dimensional Fermi gas at finite temperature with attractive short-range interactions. Using the virial expansion, which provides a controlled approach at high temperatures, we determine the spectral function and contact…

Quantum Gases · Physics 2014-01-08 V. Ngampruetikorn , J. Levinsen , Meera M. Parish