Efimov three-body states on top of a Fermi sea

Nygaard, Nicolai; Zinner, N. T.

doi:10.1088/1367-2630/16/2/023026

Cited by 28 publications

(49 citation statements)

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“…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.…”

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confidence: 99%

Visualizing the Efimov Correlation in Bose Polarons

2017

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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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Visualizing the Efimov Correlation in Bose Polarons

2017

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“…Experimentally, the Fermi polaron [20][21][22][23][24][25] and the Bose polaron [26][27][28] have been successfully explored in ultracold gases, both of which exhibit the attractive and repulsive branches signifying the two-body correlations. Nevertheless, the signature of Efimov physics has not been reported in existing experiments, despite a number of theoretical proposals of dominating three-body correlations in polaron systems [29][30][31][32][33][34][35][36][37].…”

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Enhancing the Efimov correlation in Bose polarons with large mass imbalance

Sun

Cui

2017

Phys. Rev. A

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We study the effect of Efimov physics (in the few-body sector) to the spectral response of Bose polaron, a many-body system consisting of an impurity immersed in a bath of bosonic atoms. We find that the Efimov correlation can be greatly enhanced by increasing the mass ratio between the bosons and the impurity, which results in visible signatures in the rf spectrum of the polaron. Using a diagrammatic approach up to the third-order virial expansion, we show how the mass imbalance and the enhanced three-body effect modify the line shape and the width of the polaron spectrum. Moreover, we study the effect of a finite boson-boson interaction to the spectrum. Taking the realistic system of Li impurities immersed in Cs bosons with a positive Cs-Cs scattering length, we find a visible Efimov branch, which is associated with the second lowest Efimov trimer, in the polaron spectrum. In particular, by adjusting the boson density the Efimov branch can greatly hybridize with the attractive polaron branch leading to the spectrum broadening near their avoided level crossing. Our results can be directly probed in the cold atoms experiments on Li-Cs and Li-Rb Bose polarons.

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“…[34] for details on the formalism). It is important to note that we take the scattering length of all subsystems and particularly its magnetic field dependence (see below) into account in our model, both that of the two heavy-light and the heavy-heavy systems.…”

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“…[34]). Here we consider the simplest approximation where the Fermi sea is considered inert, and thus its effect is Pauli blocking of states for the Lithium atom constituent in the trimer.…”

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“…[24] for an extensive elaboration on how this is done). The bound state equations for three different atoms will generally yields a set of three coupled integral equations [34], where the ingredients are the Green's function (propagator) for a single atom and the progator for a pair of atoms, the dimer propagator. To include a background Fermi sea in one of the components, one must do two things.…”

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Efimov States in Li–Cs Mixtures within a Minimal Model

Zinner

Nygaard

2015

Few-Body Syst

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We use a minimal zero-range model for describing the bound state spectrum of three-body states consisting of two Cesium and one Lithium atom. Using a broad Feshbach resonance model for the two-body interactions, we show that recent experimental data can be described surprisingly well for particular values of the three-body parameter that governs the short-range behavior of the atomic potentials and is outside the scope of the zero-range model. Studying the spectrum as a function of the three-body parameter suggests that the lowest state seen in experiment could be influenced by finite range corrections. We also consider the question of Fermi degeneracy and corresponding Pauli blocking of the Lithium atoms on the Efimov states.Introduction. The ability to study few-body states in the low-energy regime with cold atoms has allowed the observation of Efimov three-body states [1,2] and also resonances associated with bound states of four or more particles [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The key property of these low-energy bound states is a discrete scaling symmetry [23,24] that has been difficult to observe in experiments (a very recent paper presents evidence for the observation of a second Efimov resonance in Cesium [25]). Theory shows that systems with a large mass imbalance between the bound state constituents are highly suited for studying the discrete scaling since the scaling factor becomes small and more states should be observable within experimental constraints.

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Efimov three-body states on top of a Fermi sea

Cited by 28 publications

References 62 publications

Visualizing the Efimov Correlation in Bose Polarons

Visualizing the Efimov Correlation in Bose Polarons

Enhancing the Efimov correlation in Bose polarons with large mass imbalance

Efimov States in Li–Cs Mixtures within a Minimal Model

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