Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0804.1429 · Physical Review Letters

Temperature and Final State Effects in Radio Frequency Spectroscopy Experiments on Atomic Fermi Gases

Yan He, Chih-Chun Chien, Qijin Chen, Kathryn Levin

Published Jan 14, 2009• 19 citations
arXivHTMLPDF

Abstract

We present a simple and systematic characterization of the radio frequency (rf) spectra of homogeneous, paired atomic Fermi gases at general temperatures T in the presence of final-state interactions. The spectra, consisting of possible bound states and positive as well as negative detuning (nu) continua, satisfy exactly the zeroth- and first-moment sum rules at all T. We show how to best extract the pairing gap and how to detect the nu<0 continuum arising from thermally excited quasiparticles, not yet seen experimentally. We explain semiquantitatively recent rf experiments on "bound-bound" transitions, predicting effects of varying temperature.

DOI
10.1103/physrevlett.102.020402

Related papers

Radio-frequency response of strongly interacting Fermi gases at finite temperatures

S. Y. Chang

The radio-frequency spectrum of the fermions in the unitary limit at finite temperatures is characterized by the sum-rule relations. We consider a simple picture where the atoms are removed by radio-frequency excitations from the strongly interacting states into a state of negligible interaction. We calculate the moments of the response function in the range of temperature $0.08{ϵ}_{F}<T<0.8{ϵ}_{F}$ using auxiliary field Monte Carlo technique in which continuum auxiliary fields with a density-dependent shift are used. We estimate the effects of superfluid pairing from the clock shift. We find a qualitative agreement with the pairing gap--pseudogap transition behavior. We also find within the quasiparticle picture that in order for the gap to come into quantitative agreement with the previously known value at $T=0$, the effective mass has to be ${m}^{\ensuremath{\ast}}\ensuremath{\sim}1.43m$. Finally, we discuss implications for the adiabatic sweep of the resonant magnetic field.

arXiv:0905.2072•Physical Review A•Sep 29, 2009•2 citations

Radio-frequency spectroscopy and the pairing gap in trapped Fermi gases

Yan He, Qijin Chen, Kathryn Levin

We present a theoretical interpretation of radio frequency (RF) pairing gap experiments in trapped atomic Fermi gases, over the entire range of the BCS--Bose-Einstein condensation (BEC) crossover, for temperatures above and below ${T}_{c}$. Our calculated RF excitation spectra, as well as the density profiles on which they are based, are in semiquantitative agreement with experiment. We provide a detailed analysis of the physical origin of the two different peak features seen in RF spectra, one associated with nearly free atoms at the edge of the trap, and the other with (quasi-)bound fermion pairs.

arXiv:cond-mat/0504394•Physical Review A•Jul 15, 2005•59 citations

Momentum Resolved Radio Frequency Spectroscopy in Trapped Fermi Gases

Qijin Chen, Kathryn Levin

We address recent momentum-resolved radio frequency (rf) spectroscopy experiments, showing how they yield more stringent tests than other comparisons with theory, associated with the ultracold Fermi gases. We demonstrate that, by providing a clear dispersion signature of pairing, they remove the ambiguity plaguing the interpretation of previous rf experiments. Our calculated spectral intensities are in semiquantitative agreement with the data. Even in the presence of a trap, the spectra are predicted to exhibit two BCS-like branches.

arXiv:0807.0830•Physical Review Letters•May 15, 2009•84 citations

Radio-frequency spectroscopy of trapped Fermi gases with population imbalance

Yan He, Chih-Chun Chien, Qijin Chen +1 more

Motivated by recent experiments, we address the behavior and evolution of radio-frequency (RF) spectra as temperature and polarization are varied in population-imbalanced Fermi gases from above to below ${T}_{c}$. We discuss a series of scenarios for the experimentally observed zero-temperature pseudogap phase and show how present and future RF experiments may help in its elucidation. We conclude that the experiments of Zwierlein and co-workers at the lowest $T$ may well reflect ground-state properties, but take issue with their claim that the pairing gap survives up to temperatures of the order of the degeneracy temperature ${T}_{F}$ at unitarity.

arXiv:0707.2625•Physical Review A•Jan 7, 2008•18 citations

Competition between Final-State and Pairing-Gap Effects in the Radio-Frequency Spectra of Ultracold Fermi Atoms

Andrea Perali, P. Pieri, Giancarlo Calvanese Strinati

The radio-frequency spectra of ultracold Fermi atoms are calculated by including final-state interactions affecting the excited level of the transition and compared with the experimental data. A competition is revealed between pairing-gap effects which tend to push the oscillator strength toward high frequencies away from threshold and final-state effects which tend instead to pull the oscillator strength toward threshold. As a result of this competition, the position of the peak of the spectra cannot be simply related to the value of the pairing gap, whose extraction thus requires support from theoretical calculations.

arXiv:0709.0817•Physical Review Letters•Jan 7, 2008•49 citations

Interacting Ultracold Alkali Atomic Fermion Gases and Radio-Frequency Spectroscopy

Zhenhua Yu

The last chapter focuses on radio-frequency spectroscopy of multi component fermion gases. Rf experiments of 6Li and 40K are first reviewed. We show that rf experiments essentially measure spin correlation functions, and internal symmetries of the interparticle interactions constrain the rf spectrum through sum rules. We self-consistently generate the spin correlation functions for 6Li within Hartree-Fock-BCS approximation. Our calculation reproduces the mean field shift observed in experiments for normal gases, and confirms that a second peak detected at higher frequencies in the rf spectrum at sufficiently low temperatures arises from paired fermions. We define a mean frequency shift by the sum rules, and show that it is proportional to the square of BCS pairing gap. The discrepancy between the mean shift and the peak frequency shift observed in experiment for the condensed phase lies in the broad width of the rf spectrum function.

•Jan 1, 2008•0 citations
We present a simple and systematic characterization of the radio frequency (rf) spectra of homogeneous, paired atomic Fermi gases at general temperatures T in the presence of final-state interactions. The spectra, consisting of possible bound states and positive as well as negative detuning (nu) continua, satisfy exactly the zeroth- and first-moment sum rules at all T. We show how to best extract the pairing gap and how to detect the nu<0 continuum arising from thermally excited quasiparticles, not yet seen experimentally. We explain semiquantitatively recent rf experiments on "bound-bound" transitions, predicting effects of varying temperature.
The radio-frequency spectrum of the fermions in the unitary limit at finite temperatures is characterized by the sum-rule relations. We consider a simple picture where the atoms are removed by radio-frequency excitations from the strongly interacting states into a state of negligible interaction. We calculate the moments of the response function in the range of temperature 0.08ϵF<T<0.8ϵF0.08{ϵ}_{F}<T<0.8{ϵ}_{F}0.08ϵF​<T<0.8ϵF​ using auxiliary field Monte Carlo technique in which continuum auxiliary fields with a density-dependent shift are used. We estimate the effects of superfluid pairing from the clock shift. We find a qualitative agreement with the pairing gap--pseudogap transition behavior. We also find within the quasiparticle picture that in order for the gap to come into quantitative agreement with the previously known value at T=0T=0T=0, the effective mass has to be ${m}^{\ensuremath{\ast}}\ensuremath{\sim}1.43m$. Finally, we discuss implications for the adiabatic sweep of the resonant magnetic field.
We present a theoretical interpretation of radio frequency (RF) pairing gap experiments in trapped atomic Fermi gases, over the entire range of the BCS--Bose-Einstein condensation (BEC) crossover, for temperatures above and below Tc{T}_{c}Tc​. Our calculated RF excitation spectra, as well as the density profiles on which they are based, are in semiquantitative agreement with experiment. We provide a detailed analysis of the physical origin of the two different peak features seen in RF spectra, one associated with nearly free atoms at the edge of the trap, and the other with (quasi-)bound fermion pairs.
We address recent momentum-resolved radio frequency (rf) spectroscopy experiments, showing how they yield more stringent tests than other comparisons with theory, associated with the ultracold Fermi gases. We demonstrate that, by providing a clear dispersion signature of pairing, they remove the ambiguity plaguing the interpretation of previous rf experiments. Our calculated spectral intensities are in semiquantitative agreement with the data. Even in the presence of a trap, the spectra are predicted to exhibit two BCS-like branches.
Motivated by recent experiments, we address the behavior and evolution of radio-frequency (RF) spectra as temperature and polarization are varied in population-imbalanced Fermi gases from above to below Tc{T}_{c}Tc​. We discuss a series of scenarios for the experimentally observed zero-temperature pseudogap phase and show how present and future RF experiments may help in its elucidation. We conclude that the experiments of Zwierlein and co-workers at the lowest TTT may well reflect ground-state properties, but take issue with their claim that the pairing gap survives up to temperatures of the order of the degeneracy temperature TF{T}_{F}TF​ at unitarity.
The radio-frequency spectra of ultracold Fermi atoms are calculated by including final-state interactions affecting the excited level of the transition and compared with the experimental data. A competition is revealed between pairing-gap effects which tend to push the oscillator strength toward high frequencies away from threshold and final-state effects which tend instead to pull the oscillator strength toward threshold. As a result of this competition, the position of the peak of the spectra cannot be simply related to the value of the pairing gap, whose extraction thus requires support from theoretical calculations.
The last chapter focuses on radio-frequency spectroscopy of multi component fermion gases. Rf experiments of 6Li and 40K are first reviewed. We show that rf experiments essentially measure spin correlation functions, and internal symmetries of the interparticle interactions constrain the rf spectrum through sum rules. We self-consistently generate the spin correlation functions for 6Li within Hartree-Fock-BCS approximation. Our calculation reproduces the mean field shift observed in experiments for normal gases, and confirms that a second peak detected at higher frequencies in the rf spectrum at sufficiently low temperatures arises from paired fermions. We define a mean frequency shift by the sum rules, and show that it is proportional to the square of BCS pairing gap. The discrepancy between the mean shift and the peak frequency shift observed in experiment for the condensed phase lies in the broad width of the rf spectrum function.