Abstract Dipole–dipole interaction (DDI) possesses characteristics different from the conventional isotropic s‐wave interaction in Bose‐Einstein condensates (BECs). The interplay of DDI with spin‐orbit coupling (SOC) and rotation may induce novel quantum properties. This work systematically analyzes the effects of the DDI, Weyl‐like SOC, rotation and trap anharmonicity in the ground state of two‐component BECs. The interplay of these factors leads to a kaleidoscope of quantum states, emerging in quantum defects, droplets, wheel and ring forms of density distributions, accompanied with transitions of topology of density, and manifesting a critical behavior around a revealed density‐collapse point. A bunch of exotic spin topological structures are shown, including centric vortex surrounded by layers of spin flows, compound topological structure of edge defect, and various coexistence states of skyrmions with different topological charges. In particular, quarter skyrmions and other possible fractional skyrmions are found. Rashba‐type SOC and Weyl‐like SOC are also compared. The study implies that one can manipulate both the density topology and the spin topological structure via these tunable parameters in BECs. The abundant variations of the topological structures and particularly the revealed critical behavior may provide quantum resources for potential applications in quantum metrology.
Abstract Dipole–dipole interaction (DDI) possesses characteristics different from the conventional isotropic s‐wave interaction in Bose‐Einstein condensates (BECs). The interplay of DDI with spin‐orbit coupling (SOC) and rotation may induce novel quantum properties. This work systematically analyzes the effects of the DDI, Weyl‐like SOC, rotation and trap anharmonicity in the ground state of two‐component BECs. The interplay of these factors leads to a kaleidoscope of quantum states, emerging in quantum defects, droplets, wheel and ring forms of density distributions, accompanied with transitions of topology of density, and manifesting a critical behavior around a revealed density‐collapse point. A bunch of exotic spin topological structures are shown, including centric vortex surrounded by layers of spin flows, compound topological structure of edge defect, and various coexistence states of skyrmions with different topological charges. In particular, quarter skyrmions and other possible fractional skyrmions are found. Rashba‐type SOC and Weyl‐like SOC are also compared. The study implies that one can manipulate both the density topology and the spin topological structure via these tunable parameters in BECs. The abundant variations of the topological structures and particularly the revealed critical behavior may provide quantum resources for potential applications in quantum metrology.
We consider the topological defects and spin structures of binary Bose-Einstein condensates (BECs) with Dresselhaus spin-orbit coupling (D-SOC) and dipole-dipole interaction (DDI) in an anharmonic trap. The combined effects of D-SOC, DDI and anharmonic trap on the ground-state phases of the system are analyzed. Our results show various structural phase transitions can be achieved by adjusting the magnitudes of the D-SOC and DDI. Meantime, a ground-state phase diagram is given as a function of the D-SOC and DDI strengths. In addition, we find that tuning the D-SOC and the DDI can derive novel rich topological configurations, including ghost vortex, half-quantum vortex, skyrmion pair, vertical skyrmion string and horizontal skyrmion string.
We investigate the ground-state phases and spin textures of spin–orbit-coupled dipolar pseudo-spin-1/2 Bose–Einstein condensates in a rotating two-dimensional toroidal potential. The combined effects of dipole–dipole interaction (DDI), spin–orbit coupling (SOC), rotation, and interatomic interactions on the ground-state structures and topological defects of the system are analyzed systematically. For fixed SOC strength and rotation frequency, we provide a set of phase diagrams as a function of the DDI strength and the ratio between inter- and intra-species interactions. The system can show rich quantum phases including a half-quantum vortex, symmetrical (asymmetrical) phase with quantum droplets (QDs), asymmetrical segregated phase with hidden vortices (ASH phase), annular condensates with giant vortices, triangular (square) vortex lattice with QDs, and criss-cross vortex string lattice, depending on the competition between DDI and contact interaction. For given DDI strength and rotation frequency, the increase of the SOC strength leads to a structural phase transition from an ASH phase to a tetragonal vortex lattice then to a pentagonal vortex lattice and finally to a vortex necklace, which is also demonstrated by the momentum distributions. Without rotation, the interplay of DDI and SOC may result in the formation of a unique trumpet-shaped Bloch domain wall. In addition, the rotation effect is discussed. Furthermore, the system supports exotic topological excitations, such as a half-skyrmion (meron) string, triangular skyrmion lattice, skyrmion–half-skyrmion lattice, skyrmion–meron cluster, skyrmion–meron layered necklace, skyrmion–giant-skyrmion necklace lattice, and half-skyrmion–half-antiskyrmion necklace.
Abstract We consider the topological defects and spin structures of spin-1 Bose–Einstein condensates with spin–orbit coupling (SOC) and dipole–dipole interaction (DDI) in a rotating harmonic plus quartic trap. The combined effects of SOC, DDI and rotation on the ground-state phases of the system are analyzed. Our results show that for fixed rotation frequency structural phase transitions can be achieved by adjusting the magnitudes of the SOC and DDI. A ground-state phase diagram is given as a function of the SOC and DDI strengths. It is shown that the system exhibits rich quantum phases including vortex string phase with isolated density peaks (DPs), triangular (square) vortex lattice phase with DPs, checkerboard phase, and stripe phase with hidden vortices and antivortices. For given SOC and DDI strengths, the system can display pentagonal vortex lattice with DPs, vortex necklace with DPs, and exotic topological structure composed of multi-layer visible vortex necklaces, a hidden giant vortex and hidden vortex necklaces, depending on the rotation frequency. In addition, the system sustains fascinating novel spin textures and skyrmion excitations, such as an antiskyrmion pair, antiskyrmion-half-antiskyrmion (antiskyrmion–antimeron) cluster, skyrmion–antiskyrmion lattice, skyrmion–antiskyrmion cluster, skyrmion–antiskyrmion–meron–antimeron lattice, double-layer half-antiskyrmion necklaces, and composite giant-antiskyrmion–antimeron necklaces.
Abstract Spin‐orbit coupling (SOC) has broad relevances and its interplay with other interactions and potential geometry may induce novel quantum states. This work explores exotic quantum states emerging in the ground state (GS) of a strongly‐correlated spin‐1 Bose–Einstein condensate confined in 2D concentric annular traps with SOC. In the antiferromagnetic case, the GS density manifests various patterns of distributions, including facial‐makeup states, petal states, topological fissure states, multiple‐half‐ring states and property‐distinguished vertical and horizontal stripe states. A peculiar phenomenon of density‐phase separation is noticed in the sense that the variations of density and phase tend to be independent. In ferromagnetic case, the GS exhibits a semi‐circular or half‐disk status of density embedded with vortices and antivortices. The spin distribution can self‐arrange into an array of half‐skyrmions and a half‐antiskyrmion fence separating vortex‐antivortex pairs is also found. This study indicates that one can manipulate the emergence of exotic quantum states and the locations of the topological defects via the interplay of the SOC, interactions and potential geometry and the abundant state variations might also provide potential resources for quantum metrology.
We investigate the ground-state structures of dipolar spin-orbit-coupled Bose-Einstein condensates in a toroidal trap. Combined effects of dipole-dipole interaction (DDI) and spin-orbit coupling (SOC) on the ground states of the system are discussed. A ground-state phase diagram is obtained as a function of the SOC and DDI strengths. As two new degrees of freedom, the DDI and SOC can be used to obtain the desired ground-state phases and to control the phase transition between various ground states. In particular, the system displays exotic topological structures and spin textures, such as half-quantum vortex, vortex string, vortex necklace, complex vortex lattice including giant vortex and hidden antivortex chains, different skyrmions, meron (half-skyrmion)-antimeron (half-antiskyrmion) necklace, and composite meron-antimeron lattice.
We consider a spin-1 ferromagnetic Bose–Einstein condensate with Rashba spin–orbit coupling (SOC) and dipole–dipole interaction (DDI) in a double-well potential. For the nonrotating case, the ground state of the system is obtained by using the imaginary time propagation method, and a ground-state phase diagram is given with respect to the SOC strength and the DDI strength. It is shown that the nonrotating system sustains rich exotic ground-state phases including the ox-horn phase with hidden vortices and antivortices, density droplet phase with vortex–antivortex pairs, modulated stripe phase with vortex–antivortex chains, checkerboard phase with visible vortex–antivortex chains and hidden vortex–antivortex pairs, and the triangular vortex–antivortex lattice phase. For the rotating case, the dynamics of the system is investigated by using a phenomenological dissipation model. The effects of SOC, DDI and rotation on the unique dynamic behaviors of the rotating system and the final steady-state structures are revealed and analyzed. In particular, the rotating system supports fascinating novel spin textures and skyrmion excitations, and experiences a series of topological structure transitions such as the transitions from an interlaced skyrmion–antiskyrmion lattice pair to a skyrmion–meron lattice pair and then to a meron lattice pair.