Chunqing Huang

Two-dimensional solitons and quantum droplets supported by competing self- and cross-interactions in spin-orbit-coupled condensates

We study two-dimensional (2D) matter-wave solitons in spinor Bose-Einstein condensates (BECs) under the action of the spin-orbit coupling (SOC) and opposite signs of the self- and cross-interactions. Stable 2D two-component solitons of the mixed-mode (MM) type are found if the cross-interaction between the components is attractive, while the self-interaction is repulsive in each component. Stable solitons of the semi-vortex type are formed in the opposite case, under the action of competing self-attraction and cross-repulsion. The solitons exist with the total norm taking values below a collapse threshold. Further, in the case of the repulsive self-interaction and inter-component attraction, stable 2D self-trapped modes, which may be considered as quantum droplets (QDs), are created if the beyond-mean-field Lee-Huang-Yang (LHY) terms are added to the self-repulsion in the underlying system of coupled Gross-Pitaevskii equations. Stable QDs of the MM type, of a large size with an anisotropic density profile, exist with arbitrarily large values of the norm, as the LHY terms eliminate the collapse. The effect of the SOC term on characteristics of the QDs is systematically studied. We also address the existence and stability of QDs in the case of SOC with mixed Rashba and Dresselhaus terms, which makes the density profile of the QD more isotropic. Thus, QDs in the spin-orbit-coupled binary BEC are for the first time studied in the present work.

Anisotropic semivortices in dipolar spinor condensates controlled by Zeeman splitting

Spatially anisotropic solitary vortices (AVSs), supported by anisotropic dipole-dipole interactions, were recently predicted in spin-orbit-coupled binary Bose-Einstein condensates (BECs), in the form of two-dimensional semi-vortices (complexes built of zero-vorticity and vortical components). We demonstrate that the shape of the AVSs -- horizontal or vertical, with respect to the in-plane polarization of the atomic dipole moments in the underlying BEC -- may be effectively controlled by strength

Cross-symmetry breaking of two-component discrete dipolar matter-wave solitons

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Self-trapping under two-dimensional spin-orbit coupling and spatially growing repulsive nonlinearity

of the Zeeman splitting (ZS). A transition from the horizontal to vertical shape with the increase of

Spatiotemporal solitary modes in a twisted cylinder waveguide shell with the self-focusing Kerr nonlinearity

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Matter-wave solitons supported by quadrupole–quadrupole interactions and anisotropic discrete lattices

is found numerically and explained analytically. At the transition point, the AVS assumes the shape of an elliptical ring. Mobility of horizontal AVSs is studied too, with a conclusion that, with the increase of

Dipolar bright solitons and solitary vortices in a radial lattice

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Excited states of two-dimensional solitons supported by spin-orbit coupling and field-induced dipole-dipole repulsion

, their negative effective mass changes the sign into positive via a point at which the effective mass diverges. Lastly, we report a new species of textit{inverted} AVSs, with the zero-vorticity and vortex component placed in lower- and higher-energy components, as defined by the ZS. They are excited states, with respect to the ground states provided by the usual AVSs. Quite surprisingly, inverted AVSs are stable in a large parameter region.

Two-dimensional vortex quantum droplets

We study the spontaneous symmetry breaking of dipolar Bose–Einstein condensates trapped in stacks of two-well systems, which may be effectively built as one-dimensional trapping lattices sliced by a repelling laser sheet. If the potential wells are sufficiently deep, the system is modeled by coupled discrete Gross–Pitaevskii equations with nonlocal self- and cross-interaction terms representing dipole–dipole interactions. When the dipoles are not polarized perpendicular or parallel to the lattice, the crossinteraction is asymmetric, replacing the familiar symmetric two-component solitons with a new species of cross-symmetric or -asymmetric ones. The orientation of the dipole moments and the interwell hopping rate strongly affect the shapes of the discrete two-component solitons as well as the characteristics of the cross-symmetry breaking and the associated phase transition. The sub- and super-critical types of cross-symmetry breaking can be controlled by either the hopping rate between the components or the total norm of the solitons. The effect of the interplay between the contact nonlinearity and the dipole angle on the cross-symmetry breaking is also discussed.

Two-dimensional composite solitons in Bose-Einstein condensates with spatially confined spin-orbit coupling

We develop a method for creating two- and one-dimensional (2D and 1D) self-trapped modes in binary spin-orbit-coupled Bose–Einstein condensates with the contact repulsive interaction, whose local strength grows sufficiently rapidly from the center to the periphery. In particular, an exact semi-vortex (SV) solution is found for the anti-Gaussian radial modulation profile. The exact modes are included in the numerically produced family of SV solitons. Other families, in the form of mixed modes (MMs), as well as excited states of SVs and MMs, are also produced. Although the excited states are unstable in all previously studied models, they are partially stable in the present one. In the 1D version of the system, exact solutions for the counterpart of SVs, namely, semi-dipole solitons, are also found. Families of semi-dipoles, as well as the 1D version of MMs, are produced numerically.