Self-Bound Doubly Dipolar Bose-Einstein Condensates

Abstract

We analyze the physics of self-bound droplets in a doubly dipolar Bose-Einstein condensate (DDBEC) composed by particles with both electric and magnetic dipole moments. Using the particularly relevant case of dysprosium, we show that the anisotropy of the doubly-dipolar interaction potential is highly versatile and nontrivial, depending critically on the relative orientation and strength between the two dipole moments. This opens novel possibilities for exploring intriguing quantum many-body physics. Interestingly, by varying the angle between the two dipoles we find a dimensional crossover from quasi one-dimensional to quasi two-dimensional self-bound droplets. This opens a so far unique scenario in condensate physics, in which a dimensional crossover is solely driven by interactions in the absence of any confinement.Ultracold atoms are in the forefront for probing quantum many-body physics [1][2][3] due to the ability to manipulate them using external fields and engineering both short [4] and long-range interatomic potentials [5,6]. Among them, dipolar gases [7-9] gained a lot of attention since the first realization of the dipolar Bose-Einstein condensation (DBEC) of chromium atoms [10,11]. The quest for systems with higher dipole moments paved the way for polar molecules [12], ultra cold Rydberg atoms [13], erbium [14] and dysprosium (Dy) [15] BECs. For the first two cases, it is the electric dipole moment whereas in atomic condensates it is magnetic in nature. Due to the potential applications in quantum simulation [16], computing [17], tests of fundamental symmetries [18] and tuning of collisions and chemical reactions [19], a growing interest is focusing on particles possessing both electric and magnetic dipole moments [20][21][22][23][24]. Although these studies have been mostly restricted to paramagnetic polar molecules [25][26][27][28], a recent proposal has discussed the feasibility of realizing an electric, in addition to the magnetic, dipole moment in Dy atoms [20]. The latter is particularly important step due to the experimental feasibilities in atom-based setups, and opens intriguing questions about the effect of doubly dipole-dipole interactions (DDDIs) in quantum gases.Due to its anisotropic and long-range nature, dipole-dipole interaction (DDI) results in novel phenomena in DBECs [7][8][9], including anisotropic superfluidity [29][30][31], roton-like excitations [32,33], quantum droplets [34-37] and transient supersolid states [38][39][40]. Quantum droplets have been the focus of large attention, since they result from the stabilization due to quantum fluctuations of an otherwise collapsing DBEC.In this letter, we discuss the novel physics of condensates of particles with both magnetic and electric dipole moments. Focusing on the particularly relevant case of Dy atoms, we show that the combined DDDI exhibits a non-trivial anisotropy, which may be readily controlled by means of the relative orientation and strength of both dipole moments. This nontrivial anisotropy results in an intriguing physi...

Phase diagram and post-quench dynamics in a double spin-chain system in transverse fields

“…The choice of J d = 10J s is physically realizable in polar molecules [3] and Dysprosium atoms [19] with µ d /µ 0.1 in units of D/µ B , with µ B Bohr's magneton. Note that with J d = 10J s , the next-nearest neighbour EDM-EDM interactions are of similar magnitude to the nearest neighbour MDM-MDM interactions.…”

Generation of higher harmonics in dipolar Bose–Einstein condensates trapped in periodically modulated potentials

“…In experiments with 11 Na, 7 Li, 39 K and 85 Rb BECs, contribution to the dynamics from atomic magnetic moments is usually neglected, as the corresponding dipole-dipole interactions (DDIs) are very weak [63]. On the other hand, BEC has also been created in gases of 52 Cr [64][65][66], 168 Er [67], 164 Dy [68,69] and 162 Dy [70] atoms, which carry large magnetic moments (μ ≥ 6μ B , where μ B is the Bohr magneton).…”

“…In particular, DDI may be positive in one direction and negative in another [71]. Dipolar BECs have been investigated in broad contexts, such as the existence of the quantum liquid stabilized by quantum fluctuations, spin-orbit coupling, physics of lattices beyond the standard Bose-Hubbard model, parametric oscillations, roton excitations, modulation instability, anisotropic solitons, vortex scissors oscillations, structure formation, self-bound droplets in a doubly dipolar BEC, and dipolar BEC in a bubble trap [72][73][74][75][76][77][78][79][80][81][82][83][84][85].…”

Kink-like solitons in quantum droplet

“…The dimension crossovers from 1D → 3D [43] and 2D → 3D in binary BECs have also been analysed [44]. Droplet with constituents having electric and magnetic moments have been explored [45], where it is observed that the droplets experience a crossover from the cigar to pancake shapes in terms of relative dipole orientations. A new type of droplet in binary magnetic gases has been recently found, where single component self-bound droplet can couple with other magnetic components, not in the droplet phase [46].…”