Few-body states of bosons interacting with a heavy quantum impurity

Yoshida, S.; Shi, Zhe-Yu; Levinsen, Jesper; Parish, Meera M.

doi:10.1103/physreva.98.062705

Cited by 8 publications

(20 citation statements)

References 49 publications

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“…Our findings complement recent theory predictions for localized impurities in a Bose gas, where it was found that the impurity induces a strong boson-boson repulsion even in the absence of any direct repulsive interaction [69,70]. Therefore, a picture is emerging where the ground state of the Bose polaron with short range interactions appears well described by calculations including only a few excitations of the medium.…”

Section: Discussionsupporting

confidence: 88%

Fate of the Bose polaron at finite temperature

2020

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We consider an impurity immersed in a Bose-Einstein condensate with tunable boson-impurity interactions. Such a Bose polaron has recently been predicted to exhibit an intriguing energy spectrum at finite temperature, where the ground-state quasiparticle evenly splits into two branches as the temperature is increased from zero [Guenther et al., Phys. Rev. Lett. 120, 050405 (2018)]. To investigate this theoretical prediction, we employ a recently developed variational approach that systematically includes multi-body correlations between the impurity and the finite-temperature medium, thus allowing us to go beyond previous finite-temperature methods. Crucially, we find that the number of quasiparticle branches is simply set by the number of hole excitations of the thermal cloud, such that including up to one hole yields one splitting, two holes yields two splittings, and so on. Moreover, this effect is independent of the impurity mass. We thus expect that the exact ground-state quasiparticle will evolve into a single broad peak for temperatures T > 0, with a broadening that scales as T 3/4 at low temperatures and sufficiently weak boson-boson interactions. In the zero-temperature limit, we show that our calculated ground-state polaron energy is in excellent agreement with recent quantum Monte Carlo results and with experiments. arXiv:1910.02620v1 [cond-mat.quant-gas]

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Section: Discussionsupporting

confidence: 88%

Fate of the Bose polaron at finite temperature

2020

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“…The κ ≪ 1 regime was recently investigated in Refs. [31,32]. Our goal is to describe four-and higher-body states that are universally linked to BBX Efimov trimers.…”

Section: A System Hamiltonianmentioning

confidence: 99%

“…For two-component systems, comparatively little is known about N -body states tied to Efimov trimers [11,12,[24][25][26][27][28][29][30][31][32]. Assuming that the impurity and the bosons have the same mass but are distinguishable, the fourbody system has been found to display characteristics that are similar to the single-component case [12].…”

Section: Introductionmentioning

confidence: 99%

Few-boson system with a single impurity: Universal bound states tied to Efimov trimers

Blume

2019

Phys. Rev. A

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Small weakly-bound droplets determine a number of properties of ultracold Bose and Fermi gases. For example, Efimov trimers near the atom-atom-atom and atom-dimer thresholds lead to enhanced losses from bosonic clouds. Generalizations to four-and higher-body systems have also been considered. Moreover, Efimov trimers have been predicted to play a role in the Bose polaron with large boson-impurity scattering length. Motivated by these considerations, the present work provides a detailed theoretical analysis of weakly-bound N -body clusters consisting of N − 1 identical bosons (denoted by "B") of mass m that interact with a single distinguishable impurity particle (denoted by "X") of mass M . The system properties are analyzed as a function of the mass ratio κ (values from κ = 1 to 50 are considered), where κ is equal to m/M , and the two-body s-wave scattering length aBX between the bosons and the impurity. To reach the universal Efimov regime in which the size of the BBX trimer as well as those of larger clusters is much larger than the length scales of the underlying interaction model, three different approaches are considered: resonance states are determined in the absence of BB and BBX interactions, bound states are determined in the presence of repulsive three-body boson-boson-impurity interactions, and bound states are determined in the presence of repulsive two-body boson-boson interactions. The universal regime, in which the details of the underlying interaction model become irrelevant, is identified.PACS numbers:

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“…We present the explicit form of the wave functions ζ λp and η λ in Ref. [16]. The states B † λ |0 form an orthonormal basis of the twobody Hilbert space, and thus B λ satisfies bosonic commutation relations.…”

Section: Motivated By the Above We Tackle This Problem By Ex-mentioning

confidence: 99%

“…Second, although we have introduced an extra interaction term, it has the form of a separable potential. The separability of the interaction significantly simplifies the calculation of few-body properties and allows us to derive a series of analytical results [16], which we now discuss. Trimer and tetramer energies (solid) for the twochannel model measured from the dimer energy as a function of |r0|/a.…”

Section: Motivated By the Above We Tackle This Problem By Ex-mentioning

confidence: 99%

Impurity-Induced Multibody Resonances in a Bose Gas

et al. 2018

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We investigate the problem of N identical bosons that are coupled to an impurity particle with infinite mass. For non-interacting bosons, we show that a dynamical impurity-boson interaction, mediated by a closed-channel dimer, can induce an effective boson-boson repulsion which strongly modifies the bound states consisting of the impurity and N bosons. In particular, we demonstrate the existence of two universal "multi-body" resonances, where all multi-body bound states involving any N emerge and disappear. The first multi-body resonance corresponds to infinite impurity-boson scattering length, a → +∞, while the second corresponds to the critical scattering length a * > 0 beyond which the trimer (N = 2 bound state) ceases to exist. Crucially, we show that the existence of a * ensures that the ground-state energy in the multi-body bound-state region, ∞ > a > a * , is bounded from below, with a bound that is independent of N . Thus, even though the impurity can support multi-body bound states, they become increasingly fragile beyond the dimer state. This has implications for the nature of the Bose polaron currently being studied in cold-atom experiments. arXiv:1807.09948v1 [cond-mat.quant-gas]

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Few-body states of bosons interacting with a heavy quantum impurity

Cited by 8 publications

References 49 publications

Fate of the Bose polaron at finite temperature

Fate of the Bose polaron at finite temperature

Few-boson system with a single impurity: Universal bound states tied to Efimov trimers

Impurity-Induced Multibody Resonances in a Bose Gas

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