A new many-body wave function for BCS-BEC crossover in Fermi gases

Abstract

We present a new many body formalism for BCS-BEC crossover, which represents a modification of the BCS-Leggett ground state to include 4-fermion, and higher correlations. In the BEC regime, we show how our approach contains the \textit{Petrov et al} 4-fermion behavior and associated scattering length $a_{dd}$ at short distances, and secondly reduces to composite-boson Bogoliubov physics at long distances. It reproduces the Lee-Yang term, whose numerical value is also fixed by $a_{dd}$. We have also examined the next term beyond the Lee-Yang correction in a phenomenological fashion, building on cloud size data and collective mode experiments. However, one has to view this phenomenological analysis with some caution since experiments are in a state of flux and are performed close to unitarity.

5 pages, 2 color figures

References in corpus (22)

• Observation of a Strongly-Interacting Degenerate Fermi Gas of Atoms
• Vortices and Superfluidity in a Strongly Interacting Fermi Gas
• Observation of Bose-Einstein Condensation of Molecules
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Experimental Study of the BEC-BCS Crossover Region in Lithium 6
• BCS-BEC Crossover: From High Temperature Superconductors to Ultracold Superfluids
• Evidence for Superfluidity in a Resonantly Interacting Fermi Gas
• Crossover from a molecular Bose-Einstein condensate to a degenerate Fermi gas
• Weakly bound dimers of fermionic atoms
• Collective excitations of a degenerate gas at the BEC-BCS crossover
• Equation of state of a Fermi gas in the BEC-BCS crossover: a quantum Monte Carlo study
• Heat Capacity of a Strongly-Interacting Fermi Gas
• Precise determination of ${}^6$Li cold collision parameters by radio-frequency spectroscopy on weakly bound molecules
• On the correct strong-coupling limit in the evolution from BCS superconductivity to Bose-Einstein condensation
• Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover
• Breakdown of Hydrodynamics in the Radial Breathing Mode of a Strongly-Interacting Fermi Gas
• The Dilute Bose-Einstein Condensate with Large Scattering Length
• Collective oscillations of a trapped Fermi gas near a Feshbach resonance
• Equation of state and collective frequencies of a trapped Fermi gas along the BEC-unitarity crossover
• Properties of the strongly paired fermionic condensates
• Applying BCS-BEC Crossover Theory To High Temperature Superconductors and Ultracold Atomic Fermi Gases
• Comparison between a diagrammatic theory for the BCS-BEC crossover and Quantum Monte Carlo results

Cited by in corpus (8)

• Resonantly-paired fermionic superfluids
• Three-boson problem at low energy and Implications for dilute Bose-Einstein condensates
• When Superconductivity Crosses Over: From BCS to BEC
• Comparative Study of BCS-BEC Crossover Theories above $T_c$: the Nature of the Pseudogap in Ultra-Cold Atomic Fermi Gases
• Thermodynamics and superfluid density in BCS-BEC crossover with and without population imbalance
• Comparison of Different Pairing Fluctuation Approaches to BCS-BEC Crossover
• Fermions with attractive interactions on optical lattices and implications for correlated systems
• Tunable Molecular Interactions Near an Atomic Feshbach Resonance: Stability and Collapse of a Molecular Bose-Einstein Condensate