High-temperature expansion for interacting fermions

Sun, Mingyuan; Leyronas, X.

doi:10.1103/physreva.92.053611

Cited by 29 publications

(38 citation statements)

References 29 publications

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“…These techniques are not restricted to thermodynamic quantities but can also be applied to correlation functions as well. Indeed, besides virial coefficients [56][57][58][59], diagrammatic calculations have been performed for the spectral function [60][61][62][63], the momentum distribution of Bose gases including three-body Efimov effects [59], and also the electron gas [64]. Most of these works employ a framework similar to the one introduced in Ref.…”

Section: A Diagrammatic Virial Expansionmentioning

confidence: 99%

High-temperature expansion of the viscosity in interacting quantum gases

Hofmann

2020

Phys. Rev. A

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We compute the frequency-dependent shear and bulk viscosity spectral functions of an interacting Fermi gas in a quantum virial expansion up to second quadratic order in the fugacity parameter z = e βµ , which is small at high temperatures. Calculations are carried out using a diagrammatic finite-temperature field-theory framework, in which the analytic continuation from Matsubara to real frequencies is carried out in closed analytic form. Besides the zero-frequency Drude peak, our results for the spectral functions show a broad continuous spectrum at all frequencies with an additional bound state contribution for frequencies larger than the dimer-breaking energy. Our results are consistent with various sum rules and universal high-frequency tails. In the low-frequency limit, the shear viscosity spectral function is recast as a collision integral, which reproduces known results for the static shear viscosity from kinetic theory. Our findings for the static bulk viscosity of a Fermi gas near unitarity, however, show a non-analytic dependence on the scattering length, at variance with kinetic theory.

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Section: A Diagrammatic Virial Expansionmentioning

confidence: 99%

High-temperature expansion of the viscosity in interacting quantum gases

Hofmann

2020

Phys. Rev. A

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“…For the third order contributions we follow the calculation of the diagrams from Refs. [69,70], where for a twocomponent Fermi gas there are six diagrams which con- tribute to the third order self-energy. For every slashed line we have a power of fugacity (and there will be an additional e µστ with the three body STM-equations T σ 3 ), we can see that to zeroth order in the minority fugacity, only the diagrams in Fig.…”

Section: Third-order Self Energymentioning

confidence: 99%

Breakdown of the Fermi polaron description near Fermi degeneracy at unitarity

Mulkerin

Liu

2019

Annals of Physics

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We theoretically investigate attractive and repulsive Fermi polarons in three dimensions at finite temperature and impurity concentration through the many-body T -matrix theory and hightemperature virial expansion. By using the analytically continued impurity Green's function, we calculate the direct rf spectroscopy of attractive polarons in the unitary regime. Taking the peak value of the rf spectroscopy as the polaron energy and the full width half maximum as the polaron lifetime, we determine the temperature range of validity for the quasi-particle description of Fermi polarons in the unitary limit. We also explore the temperature and impurity dependence of attractive and repulsive Fermi polarons using the direct and reverse rf spectroscopy. This methodology allows us to directly compare our results to the recent experimental data from the European Laboratory for Non-Linear Spectroscopy [F. Scazza et al., Phys. Rev. Lett. 118, 083602 (2017)].

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“…Here we adopt the diagrammatic approach in the framework of the Virial expansion [62][63][64][65][66][67]. The advantage of this method is that it is accurate at high temperature, and can systematically incorporate all the two-body and three-body contributions which allow us to extract the Efimov effect in a controllable way.…”

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confidence: 99%

Visualizing the Efimov Correlation in Bose Polarons

2017

Self Cite

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The Bose polaron is a quasi-particle of an impurity dressed by surrounding bosons. In fewbody physics, it is known that two identical bosons and a third distinguishable particle can form a sequence of Efimov bound states in the vicinity of inter-species scattering resonance. On the other hand, in the Bose polaron system with an impurity atom embedded in many bosons, no signature of Efimov physics has been reported in the existing spectroscopy measurements up to date. In this work, we propose that a large mass imbalance between a light impurity and heavy bosons can help produce visible signatures of Efimov physics in such a spectroscopy measurement. Using the diagrammatic approach in the Virial expansion to include three-body effects from pairwise interactions, we determine the impurity self-energy and its spectral function. Taking 6 Li-133 Cs system as a concrete example, we find two visible Efimov branches in the polaron spectrum, as well as their hybridizations with the attractive polaron branch. We also discuss the general scenarios for observing the signature of Efimov physics in polaron systems. This work paves the way for experimentally exploring intriguing few-body correlations in a many-body system in the near future.Top-down and bottom-up are two major approaches to studying correlations in a quantum many-body system. The cold atom system has intrinsic advantage for the bottom-up approach since it is a dilute system and the few-body problems therein are well understood. In this approach, one would like to understand how manybody physics is built up from few-body correlations. In cold atom system, one of the most intriguing three-body correlations lies in Efimov physics, which is characterized by an infinite number of trimer states nearby a two-body resonance and following a universal scaling law [1,2]. Efimov physics has been observed in a number of cold atoms experiments, while all of them are at the few-body level [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The manifestation of Efimov physics in the many-body system has yet to be observed.In this context, a convenient and non-trivial testbed is the highly-polarized ultracold gases, which consist of minority impurity atoms interacting with the majority of fermionic or bosonic atoms, respectively called the Fermi or the Bose polarons. Lots of theoretical efforts have been paid to study the Fermi polaron [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] and the Bose polaron [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]. Nearby a Feshbach resonance, a Fermi polaron displays an attractive branch [20][21][22][23][24][25]29] and a repulsive branch [26][27][28], which directly manifests two-body correlations in this system. In the past few years, the Fermi polaron has been studied by a number of experiments [52][53][54][55][56][57], while the Bose polaron has only recently been explored [58][59][60]. Most of these experiments are the injection radio-frequency spectroscopy measurements, with which both the r...

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High-temperature expansion for interacting fermions

Cited by 29 publications

References 29 publications

High-temperature expansion of the viscosity in interacting quantum gases

High-temperature expansion of the viscosity in interacting quantum gases

Breakdown of the Fermi polaron description near Fermi degeneracy at unitarity

Visualizing the Efimov Correlation in Bose Polarons

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