Supersolid Droplet Crystal in a Dipole-Blockaded Gas

Abstract

A novel supersolid phase is predicted for an ensemble of Rydberg atoms in the dipole-blockade regime, interacting via a repulsive dipolar potential softened at short distances. Using exact numerical techniques, we study the low-temperature phase diagram of this system, and observe an intriguing phase consisting of a crystal of mesoscopic superfluid droplets. At low temperature, phase coherence throughout the whole system, and the ensuing bulk superfluidity, are established through tunnelling of identical particles between neighboring droplets.

Many-body physics with alkaline-earth Rydberg lattices

“…While we have focussed on 1 S 0 Rydberg states, higher angular momentum states could also be trapped in an analogous way. Attractive interactions between non-degenerate Rydberg states are also appealing fin the context of recently proposed techniques for engineering effective ground state atom interactions by off-resonant Rydberg dressing of Bose-Einstein condenstates [51,52,53]. Quantum degeneracy was recently achieved for strontium atoms [54,55,56].…”

Excitation Spectrum of a Supersolid

“…Its dispersion closely parallels that of the excitation spectrum of a superfluid Bose-Hubbard model: it further softens as superfluidity is demoted approaching the insulating solid phase; furthermore, for the system sizes studied here, it looks linearly vanishing at the reciprocal lattice vectors, rather than featuring a finite roton minimum. The experimental realization of a SS system similar to that studied here appears possible in assemblies of ultracold atoms [7]. The double acoustic excitations, peculiar to the supersolid phase, could be detected via Bragg Spectroscopy [11,12].…”

“…Computer simulations have yielded evidence of a supersolid phase in a twodimensional system of spinless bosons in continuous space (i.e., not on a lattice), interacting through a specific class of soft-core repulsive potentials [7,8]. At low temperature and high density, despite the repulsive character of the interaction, particles pile up in clusters, in turn forming a periodic array, to which we refer as "cluster crystal" [9]: this is a lattice with a basis of K particles of the same kind and null basis vector.…”

Stable Dilute Supersolid of Two-Dimensional Dipolar Bosons

“…It is still under debate as to what extent experimental results in solid helium prove the existence of this conceptually important phase [21]. On the other hand, supersolidity is rather well understood theoretically for soft-core two-body potentials [20,[22][23][24][25][26], which can be realized, for example, in Rydberg-dressed atomic gases. However, such supersolids require a dense regime with at least several particles within the interaction range, which can be difficult to achieve.…”