Self-Bound Quantum Droplets of Atomic Mixtures in Free Space

Year: 2018

Authors: Semeghini G., Ferioli G., Masi L., Mazzinghi C., Wolswijk L., Minardi F., Modugno M., Modugno G., Inguscio M., Fattori M.

Autors Affiliation: Univ Firenze, LENS, I-50019 Sesto Fiorentino, Italy; Univ Firenze, Dipartimento Fis & Astron, I-50019 Sesto Fiorentino, Italy; CNR, Ist Nazl Ott, I-50019 Sesto Fiorentino, Italy; Univ Bologna, Dipartimento Fis & Astron, I-40127 Bologna, Italy; Univ Basque Country, UPV EHU, Dept Fis Teor & Hist Ciencia, Bilbao 48080, Spain; Basque Fdn Sci, Ikerbasque, Bilbao 48011, Spain.

Abstract: Self-bound quantum droplets are a newly discovered phase in the context of ultracold atoms. In this Letter, we report their experimental realization following the original proposal by Petrov [Phys. Rev. Lett. 115, 155302 (2015)], using an attractive bosonic mixture. In this system, spherical droplets form due to the balance of competing attractive and repulsive forces, provided by the mean-field energy close to the collapse threshold and the first-order correction due to quantum fluctuations. Thanks to an optical levitating potential with negligible residual confinement, we observe self-bound droplets in free space, and we characterize the conditions for their formation as well as their size and composition. This work sets the stage for future studies on quantum droplets, from the measurement of their peculiar excitation spectrum to the exploration of their superfluid nature.

Journal/Review: PHYSICAL REVIEW LETTERS

Volume: 120 (23)      Pages from: 235301-1  to: 235301-5

More Information: We acknowledge insightful discussions with D. Petrov, A. Simoni, S. Stringari, A. Recati, L. Tarruell, L. Tanzi, and our colleagues of the Quantum Degenerate Gases group at LENS. We thank G. Spagnolli for assistance in the early stages of the experiment. This work was supported by the ERC Starting Grant AISENS No. 258325 and by EC-H2020 Grant QUIC No. 641122. M. M. acknowledges support by the Spanish Ministry of Economy, Industry, and Competitiveness (MINECO) and the European Regional Development Fund FEDER through Grant No. FIS2015-67161-P (MINECO/FEDER, UE), and the Basque Government through Grant No. IT986-16.
KeyWords: Mixtures; Quantum electronics, Collapse threshold; Excitation spectrum; Experimental realizations; Mean-field energy; Quantum fluctuation; Repulsive forces; Spherical droplets; Ultracold atoms, Drops
DOI: 10.1103/PhysRevLett.120.235301

Citations: 403
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