Spectral response and contact of the unitary Fermi gas

Abstract

We measure radiofrequency (rf) spectra of the homogeneous unitary Fermi gas at temperatures ranging from the Boltzmann regime through quantum degeneracy and across the superfluid transition. For all temperatures, a single spectral peak is observed. Its position smoothly evolves from the bare atomic resonance in the Boltzmann regime to a frequency corresponding to nearly one Fermi energy at the lowest temperatures. At high temperatures, the peak width reflects the scattering rate of the atoms, while at low temperatures, the width is set by the size of fermion pairs. Above the superfluid transition, and approaching the quantum critical regime, the width increases linearly with temperature, indicating non-Fermi-liquid behavior. From the wings of the rf spectra, we obtain the contact, quantifying the strength of short-range pair correlations. We find that the contact rapidly increases as the gas is cooled below the superfluid transition.

References in corpus (29)

• Theory of ultracold Fermi gases
• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Observation of Fermi Polarons in a Tunable Fermi Liquid of Ultracold Atoms
• Generalized Virial Theorem and Pressure Relation for a strongly correlated Fermi gas
• Momentum sharing in imbalanced Fermi systems
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• Verification of universal relations in a strongly interacting Fermi gas
• Homogeneous Atomic Fermi Gases
• Determination of the Superfluid Gap in Atomic Fermi Gases by Quasiparticle Spectroscopy
• Viscosity and scale invariance in the unitary Fermi gas
• Pairing without Superfluidity: The Ground State of an Imbalanced Fermi Mixture
• Measurement of the Homogeneous Contact of a Unitary Fermi gas
• Determination of the Fermion Pair Size in a Resonantly Interacting Superfluid
• Theory of RF-spectroscopy of strongly interacting Fermions
• Two and Three-body Contacts in the Unitary Bose Gas
• Precise determination of the structure factor and contact in a unitary Fermi gas
• Large-N expansion for unitary superfluid Fermi gases
• Breakdown of Fermi liquid description for strongly interacting fermions
• Coherence and clock shifts in ultracold Fermi gases with resonant interactions
• Pseudo-gap pairing in ultracold Fermi atoms
• Momentum Distribution and Contact of the Unitary Fermi gas
• Enhanced paraconductivity-like fluctuations in the radio frequency spectra of ultracold Fermi atoms
• Universal contact of strongly interacting fermions at finite temperatures
• Contact and sum-rules in a near-uniform Fermi gas at unitarity
• Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas
• Short-range correlations and entropy in ultracold atomic Fermi gases
• Experimental evaluation of the nuclear neutron-proton contact
• Quantum critical transport in the unitary Fermi gas
• Connecting few-body inelastic decay to many-body correlations: a weakly coupled impurity in a resonant Fermi gas

Cited by in corpus (7)

• Contact and sum-rules in a near-uniform Fermi gas at unitarity
• The fourth- and fifth-order virial coefficients from weak-coupling to unitarity
• High Temperature Virial Expansion to Universal Quench Dynamics
• Spin Susceptibility Above the Superfluid Onset in Ultracold Fermi Gases
• Photo-excitation measurement of Tan's contact for a strongly interacting Fermi gas
• Diffusion Monte Carlo study of a spin-imbalanced two-dimensional Fermi gas with attractive interactions
• Temporal fluctuation induced order in conventional superconductors