Exotic roton excitations in quadrupolar Bose–Einstein condensates

Lahrz, M.; Lemeshko, Mikhail; Mathey, Ludwig

doi:10.1088/1367-2630/17/4/045005

Cited by 13 publications

(22 citation statements)

References 33 publications

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“…More recently, rotons have been found experimentally in two-dimensional (2D) liquid Helium-3 11 (a Fermi-liquid) and in Bose–Einstein condensates of erbium atoms subject to weak magnetic dipole–dipole interactions 12 . The roton dispersion relation has also been predicted theoretically for other ultracold dipolar 13 and quadrupolar 14 gases confined in one-dimensional (1D) and 2D geometries 15 – 17 , as well as for Rydberg-dressed atoms 18 .…”

Section: Introductionmentioning

confidence: 77%

Roton-like acoustical dispersion relations in 3D metamaterials

2021

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Roton dispersion relations have been restricted to correlated quantum systems at low temperatures, such as liquid Helium-4, thin films of Helium-3, and Bose–Einstein condensates. This unusual kind of dispersion relation provides broadband acoustical backward waves, connected to energy flow vortices due to a “return flow”, in the words of Feynman, and three different coexisting acoustical modes with the same polarization at one frequency. By building mechanisms into the unit cells of artificial materials, metamaterials allow for molding the flow of waves. So far, researchers have exploited mechanisms based on various types of local resonances, Bragg resonances, spatial and temporal symmetry breaking, topology, and nonlinearities. Here, we introduce beyond-nearest-neighbor interactions as a mechanism in elastic and airborne acoustical metamaterials. For a third-nearest-neighbor interaction that is sufficiently strong compared to the nearest-neighbor interaction, this mechanism allows us to engineer roton-like acoustical dispersion relations under ambient conditions.

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Section: Introductionmentioning

confidence: 77%

Roton-like acoustical dispersion relations in 3D metamaterials

2021

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“…Finally we note that so far the formation of angulons has been studied only for bosonic baths with contact interactions in three spatial dimensions. As for translational polarons [40,80,81], we expect the behavior of angulons to change dramatically when interacting with a fermionic bath [82], as well as with a bath featuring long-range electrostatic [3,83,84] or laser-induced [85,86] interactions, or whose motion is constrained to reduced dimensions [43,87].…”

Section: !"mentioning

confidence: 99%

Rotation of cold molecular ions inside a Bose-Einstein condensate

et al. 2016

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We use recently developed angulon theory [Phys. Rev. Lett. 114, 203001 (2015)] to study the rotational spectrum of a cyanide molecular anion immersed into Bose-Einstein condensates of rubidium and strontium. Based on ab initio potential energy surfaces, we provide a detailed study of the rotational Lamb shift and many-body-induced fine structure which arise due to dressing of molecular rotation by a field of phonon excitations. We demonstrate that the magnitude of these effects is large enough in order to be observed in modern experiments on cold molecular ions. Furthermore, we introduce a novel method to construct pseudopotentials starting from the ab initio potential energy surfaces, which provides a means to obtain effective coupling constants for low-energy polaron models.Introduction. Recently, cold molecular ions came about as a versatile platform to study single-, few-, and many-particle quantum processes [1][2][3]. As opposed to neutral molecules [3], the degree of freedom used to manipulate molecular ions -their charge -is effectively decoupled from their internal structure, and therefore even complex species can be trapped and cooled down to millikelvin translational temperatures [1]. Molecular ions can be prepared in a selected rovibrational state by optical pumping [4][5][6] or sympathetic cooling of state-selected ions [7]; they can be trapped for a few hours, with the rotational state lifetimes exceeding 15 min [7].The interest to the topic is driven, however, by numerous potential applications, such as quantum information processing [8,9], astrochemistry [10,11], as well as taming reactive collisions in the quantum regime [12,13]. Furthermore, trapped and cold molecular ions play a crucial role in precision spectroscopy [14,15], as well as tests of fundamental physics, ranging from parity violation effects [16] to search for an electric dipole moment of the electron [17,18], and possible time variation of the electron-to-proton mass ratio [19,20].Last but not least, ensembles of interacting ultracold polar molecules and ions are promising candidates to simulate complex many-body states of matter. Such simulations hold a potential to uncover the elusive nature of strongly-correlated quantum systems, such as high-temperature superconductors [21]. Recently, there appeared numerous theoretical proposals on simulating many-particle physics with ultracold molecules [3,[21][22][23], some of which have already been realized in laboratory [24]. Many of such proposals make use of long-range dipole-dipole interactions between particles in a high-density molecular sample.For neutral molecules, the latter is sometimes challenging to engineer

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“…Both theoretical and experimental situations are described in detail in the remarkable review [24]. Here we should also mention a very trustworthy theoretical work about exciton-roton excitations in two-dimensional Bose gases of quadrupoles [25]. It should be noted, that in this paper the transition from the three-dimensional case to the two-dimensional case is performed strictly and consistently.…”

Section: Introductionmentioning

confidence: 94%

“…Finally, let us note that the quantum gases with quadrupole-quadrupole interactions are widely discussed [25]. One can formulate essential properties of the quantum gas constituents as it was done in [36] in case of Fermi system with explicit example of Yb and Sr atoms.…”

Section: Introductionmentioning

confidence: 99%

Quantum Gases of Dipoles, Quadrupoles and Octupoles in Gross–Pitaevskii Formalism with Form Factor

2020

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Here, classical and quantum field theory of dipolar, axisymmetric quadrupolar and octupolar Bose gases is considered within a general approach. Dipole, axisymmetric quadrupole and octupole interaction potentials in the momentum representation are calculated. These results clearly demonstrate attraction and repulsion areas in corresponding gases. Then the Gross–Pitaevskii (GP) equation, which plays a key role in the present paper, is derived from the corresponding functional. The zoology of the form factors appearing in the GP equation is studied in details. The proper classes for the description of spatially non-uniform condensates form factors are chosen. In the Thomas–Fermi approximation a general solution of the GP equation with a quasilocal form factor is obtained. This solution has an interesting form in terms of a double rapidly converging series that universally includes all the interactions considered. Plots of condensate density functions for the exponential-trigonometric form factor are given. For the sake of completeness, in this paper we consider the GP equation with an optical lattice potential in the limit of small condensate densities. This limit does not distinguish between dipolar, quadrupolar and octupolar gases. An important analysis of the condensate stability, in other words the study of condensate excitations, is also performed in this paper. In the Gaussian approximation (from the Gross–Pitaevskii functional), a functional describing the perturbations of the condensate is derived in detail. This problem is an analog of the Bogolubov transformation used in the study of quantum Bose gases in operator formalism. For a probe wave function in the form of a plane wave, a spectrum of (Bogoliubov) excitations was obtained, from which an equation describing the threshold momentum for the emergence of instability was derived. An important result of this paper is the dependence of the threshold on the momentum of a stationary condensate. For completeness of the presentation, the approximating expression in the form of a rapidly converging series is obtained for the corresponding dependence, and plots of the corresponding series for the exponential-trigonometric form factor are given. Finally, in the conclusion a quantum hydrodynamic theory for dipolar, axisymmetric quadrupolar and octupolar gases is briefly presented, giving a clue to the experimental determination of the form factors.

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Exotic roton excitations in quadrupolar Bose–Einstein condensates

Cited by 13 publications

References 33 publications

Roton-like acoustical dispersion relations in 3D metamaterials

Roton-like acoustical dispersion relations in 3D metamaterials

Rotation of cold molecular ions inside a Bose-Einstein condensate

Quantum Gases of Dipoles, Quadrupoles and Octupoles in Gross–Pitaevskii Formalism with Form Factor

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