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A model of hybridized bosons and fermions is studied beyond the mean field approximation. The divergent boson self-energy at zero temperature makes the Cooper pairing of fermions impossible.The frequency and momentum dependence of the self-…

Condensed Matter · Physics 2009-10-28 A. S. Alexandrov

The condensation of paired fermions into superfluid states changes progressively depending on the coupling strength. At the midpoint of the crossover between Bardeen--Cooper--Schrieffer (BCS) weak-coupling and Bose--Einstein condensate…

The stability of Bose-Fermi gases trapped in an isotropic potentials at ultracold temperature is strongly influenced by the interaction between the fermions and the bosons. At zero temperature, the stability criterion is given in this paper…

Quantum Physics · Physics 2007-05-23 X. X. Yi , C. P. Sun

We determine the phase diagram of strongly correlated fermions in the crossover from Bose-Einstein condensates of molecules (BEC) to Cooper pairs of fermions (BCS) utilizing an artificial neural network. By applying advanced image…

Quantum Gases · Physics 2023-10-25 M. Link , K. Gao , A. Kell , M. Breyer , D. Eberz , B. Rauf , M. Köhl

We present an experimental study of a two component Fermi gas following an interaction quench into the superfluid phase. Starting with a weakly attractive gas in the normal phase, interactions are ramped to unitarity at a range of rates and…

Quantum Gases · Physics 2021-09-08 P. Dyke , A. Hogan , I. Herrera , C. C. N. Kuhn , S. Hoinka , C. J. Vale

Strong evidence for pairing and superfluidity has recently been found in atomic Fermi gases at the BCS-BEC crossover both in collective modes and RF excitation energies. It is argued that the scale for the effective pairing gaps measured in…

Superconductivity · Physics 2009-11-10 H. Heiselberg

We discuss topological phase transitions in ultra-cold Fermi superfluids induced by interactions and artificial spin orbit fields. We construct the phase diagram for population imbalanced systems at zero and finite temperatures, and analyze…

Quantum Gases · Physics 2012-11-13 Kangjun Seo , Li Han , C. A. R. Sá de Melo

A new mechanism is proposed to explain the puzzling damping of collective excitations, which was recently observed in the experiments of strongly interacting Fermi gases below the superfluid critical temperature on the fermionic (BCS) side…

Quantum Gases · Physics 2011-03-01 Zixu Zhang , W. Vincent Liu

We show that an interesting of pairing occurs for spin-imbalanced Fermi gases under a specific experimental condition---the spin up and spin down Fermi levels lying within the $p_x$ and $s$ orbital bands of an optical lattice, respectively.…

Quantum Gases · Physics 2014-11-20 Zixu Zhang , Hsiang-Hsuan Hung , Chiu Man Ho , Erhai Zhao , W. Vincent Liu

Simulations are performed of a small quantum system interacting with a quantum environment. The system consists of various initial states of two harmonic oscillators coupled to give normal modes. The environment is "designed" by its level…

Statistical Mechanics · Physics 2015-06-15 George L. Barnes , Michael E. Kellman

We have examined the role of the BCS pairing mechanism in the formation of the magnetic moment and henceforth a spin glass (SG) phase by studying a fermionic Sherrington-Kirkpatrick model with a local BCS coupling between the fermions. This…

Statistical Mechanics · Physics 2016-08-31 S. G. Magalhaes , Alba Theumann

The crossover from a BEC (Bose-Einstein condensation) to a BCS (Bardeen-Cooper-Schrieffer) superfluid in dilute gases of ultracold Fermi atoms creates an ideal environment to enrich our knowledge of strongly correlated many-body systems.…

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

Fermionic superfluids can undergo phase transitions into different kinds of normal regimes, loosely characterized by whether Cooper pairs remain locally stable. If the normal phase retains strong pairing fluctuations, it behaves like a…

Superconductivity · Physics 2008-10-24 Predrag Nikolic

The BCS-BEC crossover is studied in a systematic way in the broken-symmetry phase between zero temperature and the critical temperature. This study bridges two regimes where quantum and thermal fluctuations are, respectively, important. The…

Superconductivity · Physics 2007-05-23 P. Pieri , L. Pisani , G. C. Strinati

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

The pair correlations in mesoscopic systems such as $nm$-size superconducting clusters and nuclei are studied at finite temperature for the canonical ensemble of fermions in model spaces with a fixed particle number: i) a degenerate…

Atomic and Molecular Clusters · Physics 2009-11-10 S. Frauendorf , N. K. Kuzmenko , V. M. Mikhajlov , J. Sheikh

Grassmann Phase Space Theory (GSPT) is applied to the BEC/BCS crossover in cold fermionic atomic gases and used to determine the evolution (over either time or temperature) of the Quantum Correlation Functions (QCF) that specify: (a) the…

Quantum Gases · Physics 2023-02-07 B. J. Dalton , N. M. Kidwani

We determine the exact dynamics of an initial Bardeen-Cooper-Schrieffer (BCS) state of ultra-cold atoms in a deep hexagonal optical lattice. The dynamical evolution is triggered by a quench of the lattice potential, such that the…

Quantum Gases · Physics 2016-08-09 Marlon Nuske , L. Mathey , Eite Tiesinga

We present a numerical study of the interaction quench dynamics in a superfluid ultracold Fermi gas confined in a three-dimensional cigar-shaped harmonic trap. In the present paper we investigate the amplitude mode of the superfluid order…

Quantum Gases · Physics 2018-11-14 S. Hannibal , P. Kettmann , M. D. Croitoru , V. M. Axt , T. Kuhn

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…