Observation of Quantum Droplets in a Strongly Dipolar Bose Gas

Ferrier-Barbut, Igor; Kadau, Holger; Schmitt, Matthias; Wenzel, Matthias; Pfau, Tilman

doi:10.1103/physrevlett.116.215301

Cited by 615 publications

(639 citation statements)

References 33 publications

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“…Surprisingly, recent Dysprosium experiments [13,14] have revealed that destabilization of a dipolar BEC does not generally lead to collapse, as previously assumed. In these breakthrough experiments destabilization leads to the formation of stable droplets, that are only destroyed in a long time scale by three-body losses.…”

Section: Introductionmentioning

confidence: 79%

Ground-state properties and elementary excitations of quantum droplets in dipolar Bose-Einstein condensates

2016

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Recent experiments have revealed the formation of stable droplets in dipolar Bose-Einstein condensates. This surprising result has been explained by the stabilization given by quantum fluctuations. We study in detail the properties of a BEC in the presence of quantum stabilization. The ground-state phase diagram presents three main regimes: mean-field regime, in which the quantum correction is perturbative, droplet regime, in which quantum stabilization is crucial, and a multistable regime. In the absence of a multi-stable region, the condensate undergoes a crossover from the mean-field to the droplet solution marked by a characteristic growth of the peak density that may be employed to clearly distinguish quantum stabilization from other stabilization mechanisms. Interestingly quantum stabilization allows for three-dimensionally self-bound condensates. We characterized these self-bound solutions, and discuss their realization in experiments. We conclude with a discussion of the lowest-lying excitations both for trapped condensates, and for self-bound solutions.

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Section: Introductionmentioning

confidence: 79%

Ground-state properties and elementary excitations of quantum droplets in dipolar Bose-Einstein condensates

2016

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“…Among these are the roton driven fluid to crystalline quantum phase transition [1], dipolar droplet formation [2,3], insulators with fractional filling and supersolid phases of dipoles in optical lattices [4] to name only a few. Ultracold polar molecules promise particularly large dipolar interactions due to their large dipole moments.…”

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confidence: 99%

Modeling the adiabatic creation of ultracold polar 23Na40K molecules

et al. 2018

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In this work we model and realize stimulated Raman adiabatic passage (STIRAP) in the diatomic 23 Na 40 K molecule from weakly bound Feshbach molecules to the rovibronic ground state via the |v d = 5, J = Ω = 1 excited state in the d 3 Π electronic potential. We demonstrate how to set up a quantitative model for polar molecule production by taking into account the rich internal structure of the molecules and the coupling laser phase noise. We find excellent agreement between the model predictions and the experiment, demonstrating the applicability of the model in the search of an ideal STIRAP transfer path. In total we produce 5000 fermionic groundstate molecules. The typical phase-space density of the sample is 0.03 and induced dipole moments of up to 0.54 Debye could be observed.Dipolar quantum gases allow for the realization of intriguing new quantum many-body systems and associated phenomena due to their anisotropic and long-range interactions. Among these are the roton driven fluid to crystalline quantum phase transition [1], dipolar droplet formation [2,3], insulators with fractional filling and supersolid phases of dipoles in optical lattices [4] to name only a few. Ultracold polar molecules promise particularly large dipolar interactions due to their large dipole moments.The standard procedure for creating molecules at high phase-space density starts with a mixture of two atomic species close to quantum degeneracy. The two species are then initially adiabatically associated into a weakly bound Feshbach molecular state |F B [5]. From there they can be transferred into the final, electronic, vibrational and rotational (rovibronic) ground state using stimulated Raman adiabatic passage (STIRAP) [6,7]. This last step involves coupling the initial and final state to a common intermediate, electronically excited molecular state. Both |F B and the intermediate state need to be chosen with care in order to allow for a high efficiency in the transfer and thus to preserve the phase space density of the ultracold mixture. This approach has been applied successfully to dipolar KRb [8] to the ground state compared to the STIRAP scheme employed in [11]. We develop a Hamiltonian model to describe the adiabatic transfer in all required details to achieve a quantitative description. In addition to the molecular structure analysis done for different bialkali systems [14,15] we include the complex light coupling into the analysis. This results in a multi-level, crosscoupled model that is intimately related to the work of the Bergmann group on STIRAP in multilevel systems [16] but is specific to the alkali-alkali molecule formation. We investigate how to maximize the STIRAP transfer efficiency for a given intermediate state manifold by optimizing pulse durations and one-photon detuning. We find excellent agreement between simulation and experiment. Finally, we demonstrate ground state molecule creation with a large electric dipole moment of up to 0.54 Debye. I. MOLECULAR LEVEL STRUCTURE AND HAMILTONIAN MODELIn our model we us...

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“…The observability of microscopic quantum effects involving a substantial fraction of the particles in a coherent macroscopic setting generally requires going beyond MF, for example, at low density in one dimension (1D) [1,2] or high density in three dimensions (3D). In 3D systems, the high-density Lee-Huang-Yang corrections, which are induced by quantum correlations, were realized experimentally using the Feshbach resonance [3] and in the spectacular form of "quantum droplets" in dipolar [4][5][6] and isotropic [7] bosonic gases, i.e., as self-trapped states stabilized against the collapse by the beyond-MF selfrepulsion. This stabilization was predicted in Refs.…”

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confidence: 99%

Dissociation of One-Dimensional Matter-Wave Breathers due to Quantum Many-Body Effects

et al. 2017

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We use the ab initio Bethe ansatz dynamics to predict the dissociation of one-dimensional cold-atom breathers that are created by a quench from a fundamental soliton. We find that the dissociation is a robust quantum many-body effect, while in the mean-field (MF) limit the dissociation is forbidden by the integrability of the underlying nonlinear Schrödinger equation. The analysis demonstrates the possibility to observe quantum many-body effects without leaving the MF range of experimental parameters. We find that the dissociation time is of the order of a few seconds for a typical atomic-soliton setting. DOI: 10.1103/PhysRevLett.119.220401 Under normal conditions, interacting quantum Bose gases do not readily exhibit signatures of their corpuscular nature, but rather follow the behavior predicted by meanfield (MF) theory. The observability of microscopic quantum effects involving a substantial fraction of the particles in a coherent macroscopic setting generally requires going beyond MF, for example, at low density in one dimension (1D) [1,2] or high density in three dimensions (3D). In 3D systems, the high-density Lee-Huang-Yang corrections, which are induced by quantum correlations, were realized experimentally using the Feshbach resonance [3] and in the spectacular form of "quantum droplets" in dipolar [4][5][6] and isotropic [7] bosonic gases, i.e., as self-trapped states stabilized against the collapse by the beyond-MF selfrepulsion. This stabilization was predicted in Refs. [8][9][10]. Quantum effects involving a macroscopic number of atoms in collapsing attractive 3D gases and colliding condensates were also observed [11][12][13][14][15] and analyzed [16,17] in the MF density range.A generic opportunity to observe beyond-MF effects arises when a particular symmetry of the MF dynamics, which prohibits a certain effect, is broken at the microscopic level, thus making observation of the effect possible. For instance, the scale invariance in the dynamics of a harmonically trapped 2D Bose gas nullifies the interaction-induced shift of the frequency of monopole excitations for all excitation amplitudes; however, this scale invariance is broken by the quantum many-body Hamiltonian, leading to a small shift, albeit discernible on a zero background [18]. In this context, the symmetry breaking by the secondary quantization may be considered as a manifestation of a general phenomenon known as the quantum anomaly [19]. In this Letter we develop a similar strategy for predicting beyond-MF effects in the one-dimensional (1D) self-attractive Bose gas in a MF range of parameters. The respective MF equation amounts to the nonlinear Schrödinger (NLS) equation, integrable by the inverse-scattering transform [20]. The NLS rigidly links the structure of a time-dependent solution to its initial form, with many features of the latter rendered identifiable in the former. In particular, a sudden increase of the strength of the attractive coupling constant by a factor of 4, i.e., an interaction quench, converts a fundamental s...

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Observation of Quantum Droplets in a Strongly Dipolar Bose Gas

Cited by 615 publications

References 33 publications

Ground-state properties and elementary excitations of quantum droplets in dipolar Bose-Einstein condensates

Ground-state properties and elementary excitations of quantum droplets in dipolar Bose-Einstein condensates

Modeling the adiabatic creation of ultracold polar 23Na40K molecules

Dissociation of One-Dimensional Matter-Wave Breathers due to Quantum Many-Body Effects

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