Dynamic structure factor of a strongly correlated Fermi superfluid within a density functional theory approach

Abstract

We theoretically investigate the dynamic structure factor of a strongly interacting Fermi gas at the crossover from Bardeen-Cooper-Schrieffer superfluids to Bose-Einstein condensates, by developing an improved random phase approximation within the framework of a density functional theory - the so-called superfluid local density approximation. Compared with the previous random-phase-approximation studies based on the standard Bogoliubov-de Gennes equations, the use of the density functional theory greatly improves the accuracy of the equation of state at the crossover, and leads to a better description of both collective Bogoliubov-Anderson-Goldstone phonon mode and single-particle fermionic excitations at small transferred momentum. Near unitarity, where the s-wave scattering length diverges, we show that the single-particle excitations start to significantly contribute to the spectrum of dynamic structure factor once the frequency is above a threshold of the energy gap at $2\Delta$. The sharp rise in the spectrum at this threshold can be utilized to measure the pairing gap $\Delta$. Together with the sound velocity determined from the phonon branch, the dynamic structure factor provides us some key information of the crossover Fermi superfluid. Our predictions could be examined in experiments with ${}^6$Li or ${}^{40}$K atoms using Bragg spectroscopy.

arXiv comment13 pages, 7 figures

References in corpus (63)

• Many-Body Physics with Ultracold Gases
• Theory of ultracold Fermi gases
• BCS-BEC Crossover: From High Temperature Superconductors to Ultracold Superfluids
• Revealing the Superfluid Lambda Transition in the Universal Thermodynamics of a Unitary Fermi Gas
• Exploring the Thermodynamics of a Universal Fermi Gas
• Equation of state of a Fermi gas in the BEC-BCS crossover: a quantum Monte Carlo study
• The Unitary Fermi Gas: From Monte Carlo to Density Functionals
• The BCS-BEC Crossover in a Gas of Fermi Atoms with a Feshbach Resonance
• Universal Thermodynamics of Degenerate Quantum Gases in the Unitarity Limit
• The Equation of State of a Low-Temperature Fermi Gas with Tunable Interactions
• Thermodynamics of the BCS-BEC crossover
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Asymmetric Two-component Fermion Systems in Strong Coupling
• Spin 1/2 Fermions in the Unitary Regime: A Superfluid of a New Type
• Precision Measurements of Collective Oscillations in the BEC-BCS Crossover
• Quantum Fluctuations in the Superfluid State of the BCS-BEC Crossover
• Collective mode of homogeneous superfluid Fermi gases in the BEC-BCS crossover
• Determination of the Superfluid Gap in Atomic Fermi Gases by Quasiparticle Spectroscopy
• Epsilon expansion for a Fermi gas at infinite scattering length
• Bragg spectroscopy of a strongly interacting Fermi gas
• Equation of state of a superfluid Fermi gas in the BCS-BEC crossover
• Virial expansion for a strongly correlated Fermi gas
• Pairing without Superfluidity: The Ground State of an Imbalanced Fermi Mixture
• Superfluidity and collective modes in a uniform gas of Fermi atoms with a Feshbach resonance
• Measurement of the Entropy and Critical Temperature of a Strongly Interacting Fermi Gas
• Collective modes and ballistic expansion of a Fermi gas in the BCS-BEC crossover
• Local Density Functional Theory for Superfluid Fermionic Systems: The Unitary Gas
• Universal thermodynamics of strongly interacting Fermi gases
• Auxiliary Field quantum Monte Carlo for Strongly Paired Fermions
• Virial expansion for a strongly correlated Fermi system and its application to ultracold atomic Fermi gases
• Resonantly Interacting Fermions In a Box
• Critical Temperature Curve in the BEC-BCS Crossover
• Time-Dependent Density Functional Theory and the Real-Time Dynamics of Fermi Superfluids
• Probing the Spectral Function Using Momentum Resolved Radio Frequency Spectroscopy in Trapped Fermi Gases
• Polarization Measurements and the Pairing Gap in the Universal Regime
• Generation and Dynamics of Quantized Vortices in a Unitary Fermi Superfluid
• Pseudo-gap pairing in ultracold Fermi atoms
• Local Density Approximation for Systems with Pairing Correlations
• Low energy Collective Modes of a Superfluid Trapped atomic Fermi Gas
• Energy Density Functional Approach to Superfluid Nuclei
• Short-distance and short-time structure of a unitary Fermi gas
• Molecular signatures in the structure factor of an interacting Fermi gas
• A self-consistent theory of atomic Fermi gases with a Feshbach resonance at the superfluid transition
• Twin peaks in rf spectra of Fermi gases at unitarity
• Dynamic structure factor of a superfluid Fermi gas
• Density and spin response of a strongly-interacting Fermi gas in the attractive and quasi-repulsive regime
• Establishing the Presence of Coherence in Atomic Fermi Superfluids: Spin-Flip and Spin-Preserving Bragg Scattering at Finite Temperatures
• Quantitative comparison between theoretical predictions and experimental results for Bragg spectroscopy of a strongly interacting Fermi superfluid
• Collective oscillations of a confined Bose gas at finite temperature in the random-phase approximation
• Dynamic density and spin responses of a superfluid Fermi gas in the BCS-BEC crossover: Path integral formulation and pair fluctuation theory
• Validating Simple Dynamical Simulations of the Unitary Fermi Gas
• Local observation of pair-condensation in a Fermi gas at unitarity
• Density and spin response function of a normal Fermi gas at unitarity
• Predicting Energies of Small Clusters from the Inhomogeneous Unitary Fermi Gas
• Universal dynamic structure factor of a strongly correlated Fermi gas
• Theories of Linear Response in BCS Superfluids and How They Meet Fundamental Constraints
• Dynamic response of strongly correlated Fermi gases in the quantum virial expansion
• Ground-state energy of the unitary Fermi gas from the epsilon expansion
• Beyond Gaussian pair fluctuation theory for strongly interacting Fermi gases
• Dynamic structure function of a cold Fermi gas at unitarity
• Quantum Monte Carlo study of strongly interacting Fermi gases
• Many-body theories of density response for a strongly correlated Fermi gas
• Response function of strongly interacting Fermi gas in a virial expansion

Cited by in corpus (9)

• Excitation Spectrum and Superfluid Gap of an Ultracold Fermi Gas
• Visualizing the BEC-BCS crossover in the two-dimensional Fermi gas: pairing gaps and dynamical response functions from ab initio computations
• Low-momentum dynamic structure factor of a strongly interacting Fermi gas at finite temperature: The Goldstone phonon and its Landau damping
• Dynamical structure factors of a two-dimensional Fermi superfluid within random phase approximation
• Static response, collective frequencies and ground state thermodynamical properties of spin saturated two-component cold atoms and neutron matter
• Structure factors and quantum geometry in multiband BCS superconductors
• A universal pairing gap measurement proposal by dynamical excitations in 2D doped attractive Fermi-Hubbard model with spin-orbit coupling
• Dynamical structure factor and a new method to measure the pairing gap in two-dimensional attractive Fermi-Hubbard model
• Small amplitude collective modes of a finite-size unitary Fermi gas in deformed traps