Two polaron flavors of the Bose-Einstein condensate impurity

Blinova, Alina; Boshier, M. G.; Timmermans, Eddy

doi:10.1103/physreva.88.053610

Cited by 44 publications

(62 citation statements)

References 31 publications

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“…We note that the function f I is positive definite along the attractive branch, whereas it changes sign at the value r = b on the repulsive branch. For positive values of b the nodal surface in the many-body trial wave function ψ T (R), which originates from the choice, (22), of the Jastrow correlation term, allows one to discriminate between the ground-state attractive branch and the excited-state repulsive branch.…”

Section: Quantum Monte Carlo Methodsmentioning

confidence: 99%

“…However, so far, there have been no studies exploiting Feshbach resonances to increase the strength of interspecies interactions or measuring basic polaron properties such as their binding energy, lifetime, and effective mass. On the theoretical side, the self-localization of Bose polarons was investigated using mean-field approaches [9][10][11]21,22] as well as Feynman's variational method applied to the effective Hamiltonian describing the impurity [12,23]. Starting from the Fröhlich Hamiltonian other studies have focused on the calculation of the radio-frequency response of the polaron [24] and of its binding energy and effective mass using renormalization-group [25] and diagrammatic Monte Carlo [26] methods.…”

Section: Introductionmentioning

confidence: 99%

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Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

2015

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We investigate the properties of an impurity immersed in a dilute Bose gas at zero temperature using quantum Monte Carlo methods. The interactions between bosons are modeled by a hard-sphere potential with scattering length a, whereas the interactions between the impurity and the bosons are modeled by a short-range, square-well potential where both the sign and the strength of the scattering length b can be varied by adjusting the well depth. We characterize the attractive and the repulsive polaron branch by calculating the binding energy and the effective mass of the impurity. Furthermore, we investigate the structural properties of the bath, such as the impurity-boson contact parameter and the change of the density profile around the impurity. At the unitary limit of the impurity-boson interaction, we find that the effective mass of the impurity remains smaller than twice its bare mass, while the binding energy scales with 2 n 2/3 /m, where n is the density of the bath and m is the common mass of the impurity and the bosons in the bath. The implications for the phase diagram of binary Bose-Bose mixtures at low concentrations are also discussed.

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Section: Quantum Monte Carlo Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

2015

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“…In this paper, we study theoretically a polaron system that consists of an impurity atom confined to a species-selective optical lattice and a homogeneous BEC. The rich toolbox available in the field of ultracold atoms has already made possible a detailed experimental study of Fermi polarons [9][10][11][12][13][14] and stimulated active theoretical study of both Fermi [14][15][16][17][18] and Bose polarons [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. First experiments have also started to explore physics connected to the Bose polaron [34][35][36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Bloch oscillations of bosonic lattice polarons

et al. 2014

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We consider a single-impurity atom confined to an optical lattice and immersed in a homogeneous Bose-Einstein condensate (BEC). Interaction of the impurity with the phonon modes of the BEC leads to the formation of a stable quasiparticle, the polaron. We use a variational mean-field approach to study dispersion renormalization and derive equations describing nonequilibrium dynamics of polarons by projecting equations of motion into mean-field-type wave functions. As a concrete example, we apply our method to study dynamics of impurity atoms in response to a suddenly applied force and explore the interplay of coherent Bloch oscillations and incoherent drift. We obtain a nonlinear dependence of the drift velocity on the applied force, including a sub-Ohmic dependence for small forces for dimensionality d > 1 of the BEC. For the case of heavy impurity atoms, we derive a closed analytical expression for the drift velocity. Our results show considerable differences with the commonly used phenomenological Esaki-Tsu model.

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“…For example, the motion of a single impurity in a BEC can probe the superfluid dynamics [1][2][3], while an ionic impurity in a BEC can form a mesoscopic molecular ion [4]. Due to the selfenergy induced by phonons (excitations of the BEC), a neutral impurity can self-localize in both a homogeneous and a harmonically trapped BEC [5][6][7], which sheds light on polaron physics [8,9]. Exchanging phonons between multiple impurities induces an attractive Yukawa potential between each pair of impurities [10,11], which leads to the so called "co-self-localization" [12] and is related to forming bipolarons and multipolarons [13].…”

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confidence: 99%

Rydberg Electrons in a Bose-Einstein Condensate

2015

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We investigate a hybrid system composed of ultracold Rydberg atoms immersed in an atomic Bose-Einstein condensate (BEC). The coupling between the Rydberg electrons and BEC atoms leads to the excitation of phonons, the exchange of which induces Yukawa interaction between Rydberg atoms. Due to the small electron mass, the effective charge associated with this quasiparticle-mediated interaction can be large, while its range is equal to the healing length of the BEC, which can be tuned by adjusting the scattering length of the BEC atoms. We find that for small healing lengths, the distortion of the BEC can "image" the wave function density of the Rydberg electron, while large healing lengths induce an attractive Yukawa potential between the two Rydberg atoms that can form a new type of ultra-long-range molecule. We discuss both cases for a realistic system.Impurities in a Bose-Einstein condensate (BEC) have attracted much attention and motivated the investigation of a wide range of phenomena. For example, the motion of a single impurity in a BEC can probe the superfluid dynamics [1][2][3], while an ionic impurity in a BEC can form a mesoscopic molecular ion [4]. Due to the selfenergy induced by phonons (excitations of the BEC), a neutral impurity can self-localize in both a homogeneous and a harmonically trapped BEC [5][6][7], which sheds light on polaron physics [8,9]. Exchanging phonons between multiple impurities induces an attractive Yukawa potential between each pair of impurities [10,11], which leads to the so called "co-self-localization" [12] and is related to forming bipolarons and multipolarons [13]. Recent experiments, where an atom of a BEC is excited into a Rydberg state [14] to study phonon excitations and collective oscillations, open the door to exploration of the electron-phonon coupling in ultracold degenerate gases, a phenomenon responsible for the formation of Cooper pairs of two repelling electrons in BCS superconductivity [15].In this Letter, we study Rydberg atoms immersed in a homogeneous BEC, as sketched in Fig. 1(a). Rydberg atoms consist of an ion core and a highly excited electron with its oscillatory wave function Ψ e extending to large distances of the order of ∼n 2 a 0 (n: principle quantum number, a 0 : Bohr radius). As pointed out by Fermi [16], the interaction between the quasi-free electron at x and a ground state atom at r can be approximated at low scattering energies by a contact interaction parametrized by an energy-dependent s-wave scattering lengthWhile the s-wave approximation is valid for qualitative analysis, we include higher-partial wave contributions for quantitative results [17]. A s (k) depends on the scattering energy via the local wave number k(r) given by where R y is the Rydberg constant, 0 the vacuum permittivity, e and m e the charge and mass, respectively, of the electron with angular momentum e and quantum defect δ e . For low-e state, Eq. (1) gives an effective interaction between Rydberg and ground state atoms aswhich leads to an attraction and formation of ...

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Two polaron flavors of the Bose-Einstein condensate impurity

Cited by 44 publications

References 31 publications

Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

Impurity in a Bose-Einstein condensate: Study of the attractive and repulsive branch using quantum Monte Carlo methods

Bloch oscillations of bosonic lattice polarons

Rydberg Electrons in a Bose-Einstein Condensate

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