Thermodynamic signatures of the polaron-molecule transition in a Fermi gas

Parish, Meera M.; Adlong, Haydn S.; Liu, Weizhe Edward; Levinsen, Jesper

doi:10.1103/physreva.103.023312

Cited by 22 publications

(20 citation statements)

References 70 publications

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“…1 we show the impurity spectral function A(k, ω) ≡ −(1/π)ImG(k, ω) at zero momentum k = 0 as a function of the dimensionless impurity-atom interaction 1/(k F a ↑ ). For a negligible pairing gap in (a), we find the typical spectrum for a Fermi polaron with both attractive branch and repulsive branch [25], and a narrow molecule-hole continuum in between [25,43]. There are notable changes in the spectrum when we take a unitary Fermi gas as the background with a significant (mean-field) pairing gap ∆ ≃ 0.69ε F .…”

Section: Resultsmentioning

confidence: 83%

“…As the manyparticle background is barely affected by the existence of a single impurity, we may concentrate on the impurity only. As a result, it is possible to make a quantitative comparison between experimental data and theoretical predictions [1,3,6,13,37,39,43,44], enabling us to examine in a stringent way different approximate quantum many-particle theories [17,19,22,41].…”

Section: Introductionmentioning

confidence: 99%

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Crossover polarons in a strongly interacting Fermi superfluid

Hu,

Wang,

Zhou

et al. 2021

Preprint

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We theoretically investigate the zero-temperature quasiparticle properties of a mobile impurity immersed in a strongly interacting Fermi superfluid at the crossover from a Bose-Einstein condensate (BEC) to a Bardeen-Cooper-Schrieffer (BCS) superfluid. Termed BEC-BCS crossover polaron, or crossover polaron in short, this quasiparticle couples to elementary excitations of a many-body background and therefore could provide a useful probe of the underlying strongly interacting Fermi superfluid. Due to the existence of a significant pairing gap ∆, we find that the repulsive polaron branch becomes less well-defined. In contrast, the attractive polaron branch is protected by the pairing gap and becomes more robust at finite momentum. It remains as a delta-function peak in the impurity spectral function below a threshold 2∆. Above the threshold, the attractive polaron enters the particle-hole continuum and starts to get damped. We predict the polaron energy, residue and effective mass for realistic Bose-Fermi mixtures, where the minority bosonic atoms play the role of impurity. These results are practically useful for future cold-atom experiments on crossover polarons.

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Section: Resultsmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Crossover polarons in a strongly interacting Fermi superfluid

Hu,

Wang,

Zhou

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…We therefore need to take Cauchy principle value of the integral. This numerical difficulty does not arise in the finite-temperature variational approach [41,43,45],…”

Section: A Numerical Calculationsmentioning

confidence: 99%

“…The latter may suffer from some uncontrollable errors, since, strictly speaking, the numerical analytic continuation is not a well-defined procedure [35,48]. Alternatively, an interesting finitetemperature variational approach has recently been proposed by Meera Parish and her collaborators [41,43,45]. By solving the Chevy ansatz (extended to finite temperature) at the level of one-particle-hole excitation and keeping a sufficiently large number of discrete eigenstates [41], both short-time dynamics and rf-spectroscopy of Fermi polarons at finite temperature have been investigated in detail.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, we aim to present a systematic study of quasiparticle properties of both attractive and repulsive Fermi polarons, by using the conventional nonself-consistent many-body T -matrix theory in the singleimpurity limit [24,28]. The theory is fully equivalent to the finite-temperature variational approach [41,45], but has the advantage and simplicity of avoiding a small spectral broadening parameter, which might be needed in the calculations of spectral function and spectroscopy. As we work directly in the real-frequency domain, our calculations are also free from any potential errors arising from the numerical analytic continuation.…”

Section: Introductionmentioning

confidence: 99%

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Fermi polarons at finite temperature: Spectral function and rf-spectroscopy

Hu,

Liu

2022

Preprint

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We present a systematic study of a mobile impurity immersed in a three-dimensional Fermi sea of fermions at finite temperature, by using the standard non-self-consistent many-body T -matrix theory that is equivalent to a finite-temperature variational approach with the inclusion of one-particlehole excitation. The impurity spectral function is determined in the real-frequency domain, avoiding any potential errors due to the numerical analytic continuation in previous T -matrix calculations and the small spectral broadening parameter used in variational calculations. In the weak-coupling limit, we find that the quasiparticle decay rate of both attractive and repulsive polarons does not increase significantly with increasing temperature, and therefore Fermi polarons may remain welldefined far above Fermi degeneracy. In contrast, near the unitary limit with strong coupling, the decay rate of Fermi polarons rapidly increase and the quasiparticle picture breaks down close to the Fermi temperature. We analyze in detail the recent ejection and injection radio-frequency (rf) spectroscopy measurements, performed at Massachusetts Institute of Technology (MIT) and at European Laboratory for Non-Linear Spectroscopy (LENS), respectively. We show that the momentum average of the spectral function, which is necessary to account for the observed rfspectroscopy, has a sizable contribution to the width of the quasiparticle peak in spectroscopy. As a result, the measured decay rate of Fermi polarons could be significantly larger than the calculated quasiparticle decay rate at zero momentum. By take this crucial contribution into account, we find that there is a reasonable agreement between theory and experiment for the lifetime of Fermi polarons in the strong-coupling regime, as long as they remain well-defined.

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Fermi polarons in a driven-dissipative background medium

Cao

Zhou

2022

Sci. China Phys. Mech. Astron.

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Thermodynamic signatures of the polaron-molecule transition in a Fermi gas

Cited by 22 publications

References 70 publications

Crossover polarons in a strongly interacting Fermi superfluid

Crossover polarons in a strongly interacting Fermi superfluid

Fermi polarons at finite temperature: Spectral function and rf-spectroscopy

Fermi polarons in a driven-dissipative background medium

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