A Dual-Species Bose-Einstein Condensate with Attractive Interspecies Interactions

Abstract

We report on the production of a 41 K-87 Rb dual-species Bose-Einstein condensate with tunable interspecies interaction and we study the mixture in the attractive regime, i.e. for negative values of the interspecies scattering length a12. The binary condensate is prepared in the ground state and confined in a pure optical trap. We exploit Feshbach resonances for tuning the value of a12. After compensating the gravitational sag between the two species with a magnetic field gradient, we drive the mixture into the attractive regime. We let the system to evolve both in free space and in an optical waveguide. In both geometries, for strong attractive interactions, we observe the formation of self-bound states, recognizable as quantum droplets. Our findings prove that robust, long-lived droplet states can be realized in attractive two-species mixtures, despite the two atomic components possibly experiencing different potentials. * burchianti@lens.unifi.it † Present address: Istituto per la Protezione Sostenibile delle Piante, CNR-IPSP, 10135 Torino, Italy arXiv:2003.13362v1 [cond-mat.quant-gas]

Self-Evaporation Dynamics of Quantum Droplets in a 41K-87Rb Mixture

“…As demonstrated in a seminal paper by D. Petrov [1], ultracold quantum gases can exist in the form of self-bound droplets that do not expand even in the absence of any confinement. This liquid-like behavior, which originates from the interplay of attractive mean-field interactions and the repulsive effect of quantum fluctuations [2][3][4], was successfully observed in a number of experiments with dipolar condensates [5][6][7][8][9], homonuclear mixtures of 39 K [10][11][12][13], and recently in a heteronuclear mixture of 41 K and 87 Rb [14,15]. These findings have triggered an intense research activity on droplets properties (see, e.g., the recent reviews in Refs.…”

One-BEC-species coherent oscillations with frequency controlled by a second species atom number

“…In particular, extensive research has been carried out in small systems of two wells [40][41][42][43][44][45][46][47][48][49][50][51][52] and three-well rings [36,53]. Very importantly, the tuning of the interaction strength between atoms of distinct species, which is an accessible experimental parameter [54,55], has been suggested as a tool of control of quantum systems [35,[56][57][58][59].…”

Self-bound droplets in quasi-two-dimensional dipolar condensates

“…Quantum droplets of atomic Bose-Einstein condensates have attracted tremendous interests recently [1][2][3][4][5][6][7]. Extensive experiments have been devoted to studying their fascinating properties such as soliton to droplet crossover [8], supersolid states [9][10][11], collective excitation [12,13], Goldstone mode [14], and collision dynamics [15].…”