Rydberg-dressed Bose-Einstein Condensate Research Articles

Giant nonlocal Kerr nonlinearity and polaritonic solitons in a Rydberg-dressed Bose-Einstein condensate.

We present a scheme to generate nonlocal optical Kerr nonlinearity and polaritonic solitons via matter-wave superradiance in a Rydberg-dressed Bose-Einstein condensate (BEC). We show that the polariton spectrum of the scattered field generated by the superradiance is changed significantly due to the existence of the long-range Rydberg-Rydberg interaction between atoms, i.e. it has a roton-maxon form; moreover, the BEC structure factor displays a strong dependence on the Rydberg-dressing, which can be tuned in a controllable way. We also show that such a Rydberg-dressed BEC system can support a giant nonlocal optical Kerr nonlinearity, and hence allow the formation and stable propagation of polaritonic solitons, which have ultraslow propagation velocity and ultralow generation power. The results reported here are useful to understand the unique properties of Rydberg-dressing in BECs and have potential applications in optical information processing and transmission.

Rydberg-dressed Bose–Einstein condensate with spin–orbit coupling confined in a radially periodic potential

The use of Rydberg dressing technology to achieve long-range soft-core interaction in Bose–Einstein condensates (BECs) opens up new avenues for exploration of supersolid and its related phenomenon. We investigate the ground state of a two-component spin–orbit-coupled BECs with both long-range soft-core and contact interactions in radially periodic potentials. Our results show that the ground-state structures of the system are strongly influenced by spin–orbit coupling, contact interactions, long-range soft-core interactions, and the amplitude of the external potential. We find that such parameters can been used to induce desired ground-states structures, such as necklace structure of lump, striped standing wave, and especially ring dark soliton. Furthermore, we observe that the long-range soft-core interactions are used to manipulate the transition between miscible-immiscible phases like contact interactions. Our research provides another degree of freedom for manipulating supersolids in spin–orbit-coupled BECs.

Hyperchaos in a Bose-Hubbard Chain with Rydberg-Dressed Interactions

We study the chaos and hyperchaos of Rydberg-dressed Bose–Einstein condensates (BECs) in a one-dimensional optical lattice. Due to the long-range, soft-core interaction between the dressed atoms, the dynamics of the BECs are described by the extended Bose-Hubbard model. In the mean-field regime, we analyze the dynamical stability of the BEC by focusing on the ground state and localized state configurations. Lyapunov exponents of the two configurations are calculated by varying the soft-core interaction strength, potential bias, and length of the lattice. Both configurations can have multiple positive Lyapunov exponents, exhibiting hyperchaotic dynamics. We show the dependence of the number of the positive Lyapunov exponents and the largest Lyapunov exponent on the length of the optical lattice. The largest Lyapunov exponent is directly proportional to areas of phase space encompassed by the associated Poincaré sections. We demonstrate that linear and hysteresis quenches of the lattice potential and the dressed interaction lead to distinct dynamics due to the chaos and hyperchaos. Our work is relevant to current research on chaos as well as collective and emergent nonlinear dynamics of BECs with long-range interactions.

Quantum simulation of the Unruh effect with a Rydberg-dressed Bose-Einstein condensate

We propose a scheme for investigating the Unruh effect, i.e., the thermal radiation observed by uniformly accelerating observers or detectors, with ultracold atoms coupled by an off-resonant laser. We find that periodic modulation of the Rydberg-dressing interaction between atoms plays a significant role in the manipulation of a thermal bath in a uniformly accelerating reference frame. Our calculations show that the resulting Unruh temperature strongly depends on the driving frequency of the modulated Rydberg-dressing potential and the soft-core nature of the dressing interaction, i.e., the soft-core radius and height. These results reveal the potential applications of ultracold atoms with controllable long-range interaction in a wide variety of analog gravity phenomena.

Nonlinear dynamics of Rydberg-dressed Bose-Einstein condensates in a triple-well potential

We study nonlinear dynamics of Rydberg-dressed Bose-Einstein condensates (BECs) trapped in a triple-well potential in the semiclassical limit. The Rydberg-dressed BECs experience a long-range soft-core interaction, giving rise to strong nearest and next-nearest neighbor interactions in the triple-well system. Using mean-field Gross-Pitaevskii (GP) equations, we show that lower branches of the eigenspectra exhibit loops and level-crossings when the soft-core interaction is strong. The direct level-crossings eliminate the possibility of adiabatic Landau-Zener transitions when tilting of the triple-well potential. We demonstrate that the long-range interaction allows for self-trapping in one, two, or three wells, in a far more controllable manor than BECs with short-range or dipolar interactions. Exact quantum simulations of the three-well Bose-Hubbard model indicate that self-trapping and nonadiabatic transition can be observed with less than a dozen bosons. Our study is relevant to current research into collective excitation and nonlinear dynamics of Rydberg-dressed atoms.

Vortex structures in a rotating Rydberg-dressed Bose-Einstein condensate with the Lee-Huang-Yang correction

We numerically investigate the vortex structures in a fast rotating two-dimensional Rydberg-dressed Bose-Einstein condensate (BEC) taking into account the Lee-Huang-Yang (LHY) quantum correction. In a rotating BEC of reduced dimensionality, it is shown that there is room to tune the LHY coupling against the short- and long-range couplings. In the absence of the LHY effect, hexagonal, square, striped, and honeycomb lattices can exhibit upon increasing the long-range interaction, which can be realized in the context of superfluid (SF)-supersolid (SS) transition. In the presence of the LHY effect, competition between LHY and long-range terms results in rich lattice structures. In particular, clustering of multiple vortices can occur due to the trapping effect of the SS triangles or grids. Estimates of number of vortices in the clustering are provided.

Dynamical excitation of maxon and roton modes in a Rydberg-dressed Bose-Einstein condensate

We investigate the dynamics of a three-dimensional Bose-Einstein condensate of ultracold atomic gases with a soft-core shape long-range interaction, which is induced by laser dressing the atoms to a highly excited Rydberg state. For a homogeneous condensate, the long-range interaction drastically alters the dispersion relation of the excitation, supporting both roton and maxon modes. Rotons are typically responsible for the creation of supersolids, while maxons are normally dynamically unstable in BECs with dipolar interactions. We show that maxon modes in the Rydberg-dressed condensate, on the contrary, are dynamically stable. We find that the maxon modes can be excited through an interaction quench, i.e. turning on the soft-core interaction instantaneously. The emergence of the maxon modes is accompanied by oscillations at high frequencies in the quantum depletion, while rotons lead to much slower oscillations. The dynamically stable excitation of the roton and maxon modes leads to persistent oscillations in the quantum depletion. Through a self-consistent Bogoliubov approach, we identify the dependence of the maxon mode on the soft-core interaction. Our study shows that maxon and roton modes can be excited dynamically and simultaneously by quenching Rydberg-dressed long-range interactions. This is relevant to current studies in creating and probing exotic states of matter with ultracold atomic gases.

Anderson localization in an oscillating Rydberg-dressed condensate with random disorder

We numerically study the Anderson localization in an oscillating one-dimensional Rydberg-dressed Bose-Einstein condensate with weak random disorder in which the range of the interaction, the blockade radius ${R}_{\mathrm{c}}$, is variable. Without disorder, the uniform system can undergo a superfluid-supersolid transition at ${R}_{\text{c}}={l}_{\mathrm{c}}\ensuremath{\simeq}1.7{\ensuremath{\xi}}_{0}$ with ${\ensuremath{\xi}}_{\text{0}}$ the zero-range healing length. When ${\ensuremath{\xi}}_{0}$ exceeds the disorder correlation length ${\ensuremath{\sigma}}_{\mathrm{D}}$, we show that exponential localization occurs in the equilibrium condensate when ${R}_{\mathrm{c}}\ensuremath{\le}{l}_{\mathrm{c}}$, while Gaussian localization occurs when ${R}_{\mathrm{c}}g{l}_{\mathrm{c}}$. The latter suggests that the $k$ wave for a long-ranged interacting system could decay Gaussianly with weak random disorder.

Turbulence in a matter-wave supersolid

Quantum turbulence associated with wave and vortex dynamics is numerically investigated for a two-dimensional trapped atomic Rydberg-dressed Bose-Einstein condensate (BEC). When the coupling constant of the soft-core interaction is over a critical value, the superfluid (SF) system can transition into a hexagonal supersolid (SS) state. Based on the Gross-Pitaevskii equation approach, we have discovered a new characteristic k−13/3 scaling law for wave turbulence in the SS state, that coexists with the waveaction k−1/3 and energy k−1 cascades commonly existing in a SF BEC. The new k−13/3 scaling law implies that the SS system exhibits a negative, minus-one power energy dispersion (E ~ k−1) at the wavevector consistent with the radius of the SS droplet. For vortex turbulence, in addition to the presence of the Kolmogorov energy k−5/3 and Saffman enstrophy k−4 cascades, it is found that large amount of independent vortices and antivortices pinned to the interior of the oscillating SS results in a strong k−1 scaling at the wavevector consistent with the SS lattice constant.

Chiral Supersolid in Spin-Orbit-Coupled Bose Gases with Soft-Core Long-Range Interactions

Chirality represents a kind of symmetry breaking characterized by the noncoincidence of an object with its mirror image and has been attracting intense attention in a broad range of scientific areas. The recent realization of spin-orbit coupling in ultracold atomic gases provides a new perspective to study quantum states with chirality. In this Letter, we demonstrate that the combined effects of spin-orbit coupling and interatomic soft-core long-range interaction can induce an exotic supersolid phase in which the chiral symmetry is broken with spontaneous emergence of circulating particle current. This implies that a finite angular momentum can be generated with neither rotation nor effective magnetic field. The direction of the angular momentum can be altered by adjusting the strength of spin-orbit coupling or interatomic interaction. The predicted chiral supersolid phase can be experimentally observed in Rydberg-dressed Bose-Einstein condensates with spin-orbit coupling.

Pseudo-Arclength Continuation Algorithms for Binary Rydberg-Dressed Bose-Einstein Condensates

AbstractWe study pseudo-arclength continuation methods for both Rydberg-dressed Bose-Einstein condensates (BEC), and binary Rydberg-dressed BEC which are governed by the Gross-Pitaevskii equations (GPEs). A divide-and-conquer technique is proposed for rescaling the range/ranges of nonlocal nonlinear term/terms, which gives enough information for choosing a proper stepsize. This guarantees that the solution curve we wish to trace can be precisely approximated. In addition, the ground state solution would successfully evolve from one peak to vortices when the affect of the rotating term is imposed. Moreover, parameter variables with different number of components are exploited in curve-tracing. The proposed methods have the advantage of tracing the ground state solution curve once to compute the contours for various values of the coefficients of the nonlocal nonlinear term/terms. Our numerical results are consistent with those published in the literatures.

Dissipative preparation of spatial order in Rydberg-dressed Bose-Einstein condensates.

We propose a technique for engineering momentum-dependent dissipation in Bose-Einstein condensates with nonlocal interactions. The scheme relies on the use of momentum-dependent dark states in close analogy to velocity-selective coherent population trapping. During the short-time dissipative dynamics, the system is driven into a particular finite-momentum phonon mode, which in real space corresponds to an ordered structure with nonlocal density-density correlations. Dissipation-induced ordering can be observed and studied in present-day experiments using cold atoms with dipole-dipole or off-resonant Rydberg interactions. Because of its dissipative nature, the ordering does not require artificial breaking of translational symmetry by an optical lattice or harmonic trap. This opens up a perspective of direct cooling of quantum gases into strongly interacting phases.

Pseudospin orders in the supersolid phases in binary Rydberg-dressed Bose-Einstein condensates

We show that the five possible ordered states in a quantum spin-1/2 system with long-range exchange interactions: Neel, ladder, Peierls, coincidence, and domain states, can be realized in a binary Rydberg-dressed BEC system in the supersolid phase. In such a system, blockade phenomenon is shown to also occur for pairs of different excited-state atoms, which results in similar intra- and inter-species long-range interactions between ground-state atoms. It suggests that a pseudo spin-1/2 system can be possibly formed in the ground state of ultracold rudibium.

Quantum crystals in a trapped Rydberg-dressed Bose-Einstein condensate

Spontaneously crystalline ground states, called quantum crystals, of a trapped Rydberg-dressed Bose-Einstein condensate are numerically investigated. As a result described by a mean-field order parameter, such states simultaneously possess crystalline and superfluid properties. A hexagonal droplet lattice is observed in a quasi-two-dimensional system when dressing interaction is sufficiently strong. Onset of these states is characterized by a drastic drop of the non-classical rotational inertia proposed by Leggett [Phys. Rev. Lett. 25, 1543 (1970)]. In addition, an AB stacking bilayer lattice can also be attained. Due to an anisotropic interaction possibly induced by an external electric field, transition from a hexagonal to a nearly square droplet lattice is also observed.