Enhanced paraconductivity-like fluctuations in the radio frequency spectra of ultracold Fermi atoms

Abstract

Ultracold Fermi atoms allow the realization of the crossover from Bardeen-Cooper-Schrieffer (BCS) superconductivity to Bose- Einstein condensation (BEC), by varying with continuity the attraction between fermions of different species. In this context, radio frequency (RF) spectroscopy provides a microscopic probe to infer the nature of fermionic pairing. In the strongly-interacting regime, this pairing affects a wide temperature range comprising the critical temperature T_c, in analogy to the pseudogap physics for high-temperature superconductors. By including what are known in superconductors as "paraconductivity" fluctuations, here we calculate the RF spectra above T_c for fermions with balanced populations and compare them with available experimental data, thus revealing that the role of these fluctuations is considerably enhanced with respect to superconductors. In addition, we extract from the spectra an energy scale associated with pairing and relate it to a universal quantity recently introduced for Fermi gases.

17 pages, 5 figures

References in corpus (12)

• Observation of the Pairing Gap in a Strongly Interacting Fermi Gas
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• Exact Relations for a Strongly-interacting Fermi Gas from the Operator Product Expansion
• Determination of the Superfluid Gap in Atomic Fermi Gases by Quasiparticle Spectroscopy
• Number of closed-channel molecules in the BEC-BCS crossover
• Tomographic RF Spectroscopy of a Trapped Fermi Gas at Unitarity
• BCS-BEC crossover at finite temperature in the broken-symmetry phase
• Determination of the Fermion Pair Size in a Resonantly Interacting Superfluid
• Radio-Frequency Transitions on Weakly-Bound Ultracold Molecules
• Broad versus narrow Fano-Feshbach resonances in the BCS-BEC crossover with trapped Fermi atom
• Competition between final-state and pairing-gap effects in the radio-frequency spectra of ultracold Fermi atoms
• Final-state effects in the radio frequency spectrum of strongly interacting fermions

Cited by in corpus (16)

• Verification of universal relations in a strongly interacting Fermi gas
• Excitation spectra and rf-response near the polaron-to-molecule transition from the functional renormalization group
• Spectral response and contact of the unitary Fermi gas
• Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas
• Temperature dependence of the pair coherence and healing lengths for a fermionic superfluid throughout the BCS-BEC crossover
• Fermi polarons at finite temperature: Spectral function and rf-spectroscopy
• Pairing-gap, pseudo-gap, and no-gap phases in the radio-frequency spectra of a trapped unitary 6Li gas
• Pairing and radio-frequency spectroscopy in two-dimensional Fermi gases
• Boson-fermion pairing and condensation in two-dimensional Bose-Fermi mixtures
• Clock shifts in a Fermi gas interacting with a minority component: a soluble model
• A Composite Fermion Approach to the Ultracold Dilute Fermi Gas
• Pseudogap regime of a two-dimensional uniform Fermi gas
• Universal Relations for Fermions with Large Scattering Length
• Peaks and widths of radio-frequency spectra: An analysis of the phase diagram of ultra-cold Fermi gases
• Dimer-projection contact and the clock shift of a unitary Fermi gas
• Radio-frequency driving of an attractive Fermi gas in a one-dimensional optical lattice