Quantum-fluctuation-driven crossover from a dilute Bose-Einstein condensate to a macro-droplet in a dipolar quantum fluid

Abstract

In a joint experimental and theoretical effort, we report on the formation of a macro-droplet state in an ultracold bosonic gas of erbium atoms with strong dipolar interactions. By precise tuning of the s-wave scattering length below the so-called dipolar length, we observe a smooth crossover of the ground state from a dilute Bose-Einstein condensate (BEC) to a dense macro-droplet state of more than $10^4$ atoms. Based on the study of collective excitations and loss features, we quantitative prove that quantum fluctuations stabilize the ultracold gas far beyond the instability threshold imposed by mean-field interactions. Finally, we perform expansion measurements, showing the evolution of the normal BEC towards a three-dimensional self-bound state and show that the interplay between quantum stabilization and three-body losses gives rise to a minimal expansion velocity at a finite scattering length.

13 pages, 9 figures

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• Striped states in a many-body system of tilted dipoles
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• Onset of a modulational instability in trapped dipolar Bose-Einstein condensates
• Vortex lattices in binary Bose-Einstein condensates with dipole-dipole interactions
• Observation of Weak Collapse in a Bose-Einstein Condensate
• Dissociation of one-dimensional matter-wave breathers due to quantum many-body effects
• Phases of dipolar bosons in a bilayer geometry
• Properties of strongly dipolar Bose gases beyond the Born approximation
• Quasi-one-dimensional spin-orbit- and Rabi-coupled bright dipolar Bose-Einstein-condensate solitons
• Engineering Bright Matter-Wave Solitons of Dipolar Condensates
• Beyond mean-field properties of binary dipolar Bose mixtures at low temperatures
• Finite-Range Corrections to the Thermodynamics of the One-Dimensional Bose Gas
• The onset of nanoscale dissipation in superfluid He-4 at zero temperature: the role of vortex shedding and cavitation
• Measuring the branching ratios from the $y^8{\mathrm{P}}_{9/2}$ state to metastable states in europium
• Dipolar Bose gas with three-body interactions at finite temperature