Quantum Fluctuations in Quasi-One-Dimensional Dipolar Bose-Einstein Condensates

Abstract

Recent experiments have revealed that beyond-mean-field corrections are much more relevant in weakly-interacting dipolar condensates than in their non-dipolar counterparts. We show that in quasi-one-dimensional geometries quantum corrections in dipolar and non-dipolar condensates are strikingly different due to the peculiar momentum dependence of the dipolar interactions. The energy correction of the condensate presents not only a modified density dependence, but it may even change from attractive to repulsive at a critical density due to the surprising role played by the transversal directions. The anomalous quantum correction translates into a strongly modified physics for quantum-stabilized droplets and dipolar solitons. Moreover, and for similar reasons, quantum corrections of three-body correlations, and hence of three-body losses, are strongly modified by the dipolar interactions. This intriguing physics can be readily probed in current experiments with magnetic atoms.doi:10.1103/PhysRevLett.119.050403Introduction.-Quantum fluctuations introduce a shift of the ground-state energy of a Bose gas, which at first order is given by the well-known Lee-HuangYang (LHY) correction [1]. However, in the weaklyinteracting regime, experiments on Bose-Einstein condensates are well described within the mean-field approximation. The situation may be crucially different in the presence of competing interactions, as recently discussed in the context of Bose-Bose mixtures [2]. In that scenario, the interplay between inter-and intra-species interactions results, at the verge of mean-field instability, in a dominant LHY correction well within the weaklyinteracting regime. The LHY correction may stabilize a collapsing condensate, resulting in the formation of quantum droplets, a novel ultra-dilute liquid whose surface tension is provided by purely quantum effects.

Two-dimensional quantum droplets in dipolar Bose gases

“…We show that the system yields many surprising and interesting properties. We find that the LHY quantum corrections change their nature from repulsive to attractive due to the peculiar momentum dependence of the DDI [22], similarly to the quasi-1D droplet [18]. This unconventional behavior not only modifies the density dependence and the quantum stabilization mechanism but also unveils novel phase of matter consisting of a quantum droplet.…”

“…In a 3D case, the LHY corrections provide a term proportional to n 3/2 , where n is the peak density, that arrests the dipolar instability at high condensed density [2,[5][6][7]. In quasi-1D dipolar BEC, the LHY quantum corrections present anomalous properties due to the transversal modes and the quantum droplet is appeared only in a low density regime [18]. Quantum fluctuations play also a crucial role in stabilizing droplets in lowdimensional nondipolar Bose-Bose mixtures [19][20][21].…”

“…Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. droplet state happens at relatively high density compared to the quasi-1D system [18]. The density and the shape of the droplet are analyzed by numerically solving the underlying generalized nonlocal 2D Gross-Pitaevskii equation (GPE).…”

Harmonically trapped Bose–Bose mixtures: a quantum Monte Carlo study

“…The relevance of quantum fluctuations, which makes the density profiles to depart from the GP ones, depends on the dimensionality of the system. It is well known [28,29] that they become much more significant in the case of one-dimension, since the Lee-Huang-Yang term scales as n 1/2 instead of the three-dimensional law n 3/2 .…”

Self-bound Bose–Fermi liquids in lower dimensions

“…In lower dimensions it is expected that this life-time can be extended because of reduced phase-space available to colliding atoms. Low dimensional systems are therefore of the key interest [14][15][16][17]. In this work we study a possibility of formation of the self-bound low dimensional liquid droplets in a two component mixture of ultracold bosonic and fermionic atoms.…”