Finite-temperature behavior of the Bose polaron

Levinsen, Jesper; Parish, Meera M.; Christensen, Rasmus S.; Arlt, Jan J.; Bruun, Georg M.

doi:10.1103/physreva.96.063622

Cited by 48 publications

(50 citation statements)

References 38 publications

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“…We also find that the splitting at negative energies disappears at weak boson-impurity interactions for sufficiently large n 1/3 a B . Such behavior is consistent with weak-coupling perturbation theory in the regime a B a, where no splitting is observed [23]. Finally, we see that the spectral weight around zero energy becomes suppressed with increasing n 1/3 a B .…”

Section: Effect Of Boson Interactionssupporting

confidence: 88%

“…For the finite-temperature Bose polaron, most of the theoretical investigations have been perturbative in nature, being only valid in the limit of weak boson-impurity interactions [23,24,36,37] or at high temperatures well above the BEC critical temperature [38]. While a nonperturbative functional determinant approach has been used for Rydberg atoms in a Bose gas [39,40], the Rydberg polaron differs significantly from the canonical Bose polaron where the impurity is point-like.…”

Section: Introductionmentioning

confidence: 99%

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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: Effect Of Boson Interactionssupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Fate of the Bose polaron at finite temperature

2020

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“…Here, λ B/rel are the thermal de Broglie wavelengths at the boson and the reduced mass, respectively. At weaker interaction strengths where σ ∼ a 2 , the above relation for Γ yields a non-universal rate Γ ∝ a 2 T 2 [16,41]. Experimentally, the spectral width drops rapidly for the weaker interaction strengths probed here, down to our resolution limit, prohibiting us from discerning the scaling with temperature (see Fig.…”

mentioning

confidence: 89%

“…For a direct estimate of the quasiparticle decay rate, we can look towards precise results obtained for Bose polarons in the weakly interacting regime where 1/k n |a| 1 [41]. There, it was found that in the presence of a BEC, at T < T C , the polaron decay is driven by thermally excited bosonic quasiparticles.…”

Section: Estimate Of the Impurity Decay Ratementioning

confidence: 99%

“…Predicting the Bose polaron's fate upon entering the regime of strong impurity-boson interactions has proven a challenge even at zero temperature, yielding diverging results on its properties from the ground-state energy to the effective mass [31][32][33][34][35][36][37][38][39][40]. The complexity of describing the strongly-coupled Bose polaron increases further at non-zero temperatures [41,42]. Already for weak interactions, the decay rate of polarons has been predicted to be strongly enhanced with increasing temperature, achieving its maximal value near the BEC transition temperature of the host gas [41].…”

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Bose polarons near quantum criticality

Yan

Robens

et al. 2020

Science

218

164

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The emergence of quasiparticles in strongly interacting matter represents one of the cornerstones of modern physics. However, when different phases of matter compete near a quantum critical point, the very existence of quasiparticles comes under question. Here we create Bose polarons near quantum criticality by immersing atomic impurities in a Bose-Einstein condensate (BEC) with near-resonant interactions. Using locally-resolved radiofrequency spectroscopy, we probe the energy, spectral width, and short-range correlations of the impurities as a function of temperature. Far below the superfluid critical temperature, the impurities form well-defined quasiparticles. However, their inverse lifetime, given by their spectral width, is observed to increase linearly with temperature at the Planckian scale k B T , a hallmark of quantum critical behavior. Close to the BEC critical temperature, the spectral width exceeds the binding energy of the impurities, signaling a breakdown of the quasiparticle picture. arXiv:1904.02685v3 [cond-mat.quant-gas]

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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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Finite-temperature behavior of the Bose polaron

Cited by 48 publications

References 38 publications

Fate of the Bose polaron at finite temperature

Fate of the Bose polaron at finite temperature

Bose polarons near quantum criticality

Breakdown of the Fermi polaron description near Fermi degeneracy at unitarity

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