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Shi-Jie Yang

Publications and source records attributed to Shi-Jie Yang.

At least 19 recordsLinked to original sources
arXiv2025

Exploring Magnetic Phases in Dual-Species Mott insulating Spinor Lattice Gases

We explore the Mott insulating phases of dual-species bosonic spinor lattice gases, emphasizing the intriguing interplay between synthetic flux and inter-species spin exchange interaction. One of the species is subjected to Raman assisted tunneling, which leads to a synthetic flux within the framework of synthetic dimensions. In the deep Mott regime, the low energy physics is governed by an unconventional and highly tunable spin model, which is characterized by two distinct spin chains. The synthetic flux serves as an effective spin-orbit coupling, inducing Dzyaloshinskii-Moriya interactions in one of the spin chains. The inter-species spin exchange interaction gives rise to the inter-chain coupling embodied as an isotropic XX interaction. Using time-evolving block decimation method for tensor network states, we compute order parameters, correlation functions and structure factors to identify the ground state magnetic phases. The DM interaction in one species, when combined with the inter-species spin-exchange interaction, can induce spiral magnetic order in the second, otherwise non-chiral species. Besides, the interplay of a transverse field applied to one spin chain and the inter-species coupling can drive both spin chains into a paramagnetic phase simultaneously. These results reveal that inter-species coupling serves as a powerful conduit for transmitting magnetic correlations, enabling exotic phases beyond the single-component perspective.

cond-mat.quant-gas↗
arXiv2014

Topological bands in one-dimensional periodic potentials

We study the properties of the quantum states in the one-dimensional system with a shifted periodic potential in both the discrete model and the continuous model. With open boundary conditions, the edge states appear in the energy gaps which indicate non-trivial topological structures. The Chern numbers with respect to the Bloch vector and the potential shift angle are computed. In the limit of the continuous model, the Chern number of each band is exactly one. We demonstrate the particle number pumped by the adiabatically shift of the potential is directly related to the topological invariants.

cond-mat.mes-hall↗
arXiv2014

Resonantly enhanced coherence by laser-assisted tunneling

We study quantum coherence of strongly interacting cold bosons in a double-well potential driven by a laser field. The system is initially in a Fock state and, for either with or without a static tilting field, evolves into the coherent states. The coherence is resonantly enhanced by the photon-assisted tunneling. For the tilted wells, it reveals a two-branch pattern which corresponds to the multiple photon absorption or emission, respectively.

cond-mat.quant-gas↗
arXiv2014

Exact solitons and manifold mixing dynamics in the spin-orbit-coupled spinor condensates

We derive exact static as well as moving solitonic solutions to the one-dimensional spin-orbit-coupled F=1 Bose-Einstein condensates. The static polar soliton is shown to be the ground state by the imaginary-time evolution method. It shows a helical modulation of the order parameter due to the spin-orbit coupling. In particular, the moving soliton exhibits a periodic oscillation among the particle numbers of the hyperfine states. We further explore the temporal evolution of the static polar soliton and find that the spin-polarization exhibits dynamical oscillations. This disappearance and re-emergence of the ferromagnetic state indicates the mixing of the ferromagnetic and the antiferromagnetic manifolds.

cond-mat.quant-gas↗
arXiv2014

Stable knots in the trapped Bose-Einstein condensates

The knot of spin texture is studied within the two-component Bose-Einstein condensates which are described by the nonlinear Gross-Pitaevskii equations. We start from the non-interacting equations including an axisymmetric harmonic trap to obtain an exact solution, which exhibits a non-trivial topological structure. The spin-texture is a knot with an integral Hopf invariant. The stability of the knot is verified by numerically evolving the nonlinear Gross-Pitaevskii equations along imaginary time.

cond-mat.quant-gas↗
arXiv2013

Half-knot in the spinor condensates

We present an exact solution to the stationary coupled nonlinear Gross-Pitaevskii equations which govern the motion of the spinor Bose-Einstein condensates. The solitonic solution is a twisted half-skyrmion in the three-dimension (3D) space. By making a map from and the Cartesian coordinates to the toroidal coordinates, we demonstrate it is a linked half-unknot with a fractional Hopf charge.

cond-mat.quant-gas↗
arXiv2013

Fractional windings of the spinor condensates on a ring

We study the uniform solutions to the one-dimensional spinor Bose-Einstein condensates on a ring. These states explicitly display the associated motion of the super-current and the spin rotation, which give rise to fractional winding numbers according to the various compositions of the hyperfine states. It simultaneously yields a fractional factor to the global phase due to the gauge-spin symmetry. Our method can be applied to explore the fractional vortices by identifying the ring as the boundary of two-dimensional spinor condensates.

cond-mat.quant-gas↗
arXiv2013

Dynamical revivals of the paired superfluidity and counterflow superfluidity

The quantum dynamics of two-species bosons in an optical lattice is studied within the mean-field theory. The quantum coherence experiences periodical collapses and revivals, which depends on the relative strength of the inter-and intra-species interactions. The paired superfluidity and the counterflow superfluidity are identified and are verified by exact diagonaliztion in the two-site Hubbard model. We suggest a dynamical method of implementation and detection for the paired superfluid and the counterflow superfluidity in the optical lattices.

cond-mat.quant-gas↗
arXiv2013

Exact periodic and solitonic states in the spinor condensates

We propose a method to analytically solve the one-dimensional coupled nonlinear Gross-Pitaevskii equations which govern the motion of the spinor Bose-Einstein condensates. In a uniform external potential, the Hamiltonian comprises the kinetic energy, the linear and the quadratic Zeeman energies. Several classes of exact periodic and solitonic solutions, either in real or in complex forms, are obtained for both the F=1 and F=2 condensates. These solutions are general that contain neither approximations nor constraints on the system parameters.

cond-mat.quant-gas↗
arXiv2013

Exact temporal evolution of the two-species Bose-Einstein condensates

We construct exact stationary solutions to the one-dimensional coupled Gross-Pitaevskii equations for the two-species Bose-Einstein condensates with equal intraspecies and interspecies interaction constants. Three types of complex solutions as well as their soliton limits are derived. By making use of the SU(2) unitary symmetry, we further obtain analytical time-evolving solutions. These solutions exhibit spatiotemporal periodicity.

cond-mat.quant-gas↗
arXiv2013

Skyrmion crystals in the pseudo-spin-1/2 Bose-Einstein condensates

Exact two-dimensional solutions are constructed for the pseudo-spin-1/2 Bose-Einstein condensates which are described by the coupled nonlinear Gross-Pitaevskii equations where the intraspecies and interspecies coupling constants are assumed to be equal. The equations are decoupled by means of re-combinations of the nonlinear terms of the hyperfine states according to the spatial dimensions. These stationary solutions form various spin textures which are identified as skyrmion crystals. In a special case, the crystal of skyrmion-antiskyrmion pairs is formed in the soliton limit.

cond-mat.quant-gas↗
arXiv2012

Exact solutions to the spin-2 Gross-Pitaevskii equations

We present several exact solutions to the coupled nonlinear Gross-Pitaevskii equations which describe the motion of the one-dimensional spin-2 Bose-Einstein condensates. The nonlinear density-density interactions are decoupled by making use of the properties of Jacobian elliptical functions. The distinct time factors in each hyperfine state implies a "Lamor" procession in these solutions. Furthermore, exact time-evolving solutions to the time-dependent Gross-Pitaevskii equations are constructed through the spin-rotational symmetry of the Hamiltonian. The spin-polarizations and density distributions in the spin-space are analyzed.

cond-mat.quant-gas↗
arXiv2012

Impurity effects on the quantum coherence of a few-boson system

The impurity effects on the quantum coherence of a few-boson system are studied within the two-site Hubbard model. Periodical collapses and revivals of coherence occur in the presence of either polarized or unpolarized fermionic impurities. The relative strength $U_{BF}/U_{BB}$ of the boson-fermion versus the boson-boson interactions plays a key role in the coherence revivals. As the average filling of the impurity increases, the coherence revivals remain nearly unaffected for $U_{BF}/U_{BB}=z$ ($z\in Z$ is an integer) while the odd revival peaks are damped for $U_{BF}/U_{BB}=z+1/2$, in agreement with the experimental observations. For unpolarized fermionic impurities, the coherence revivals are irrelevant to the strength of the fermion-fermion interactions.

cond-mat.quant-gas↗
arXiv2012

Analytical solutions to the spin-1 Bose-Einstein condensates

We analytically solve the one-dimensional coupled Gross-Pitaevskii equations which govern the motion of F=1 spinor Bose-Einstein condensates. The nonlinear density-density interactions are decoupled by making use of the unique properties of the Jacobian elliptical functions. Several types of complex stationary solutions are deduced. Furthermore, exact non-stationary solutions to the time-dependent Gross-Pitaevskii equations are constructed by making use of the spin-rotational symmetry of the Hamiltonian. The spin-polarizations exhibit kinked configurations. Our method is applicable to other coupled nonlinear systems.

cond-mat.quant-gas↗
arXiv2012

Disorder effects on the quantum coherence of a many-boson system

The effects of disorders on the quantum coherence for many-bosons are studied in a double well model. For the ground state, the disorder enhances the quantum coherence. In the deep Mott regime, dynamical evolution reveals periodical collapses and revivals of the quantum coherence which is robust against the disorder. The average over variations in both the on-site energy and the interaction reveals a beat phenomenon of the coherence-decoherence oscillation in the temporal evolution.

cond-mat.quant-gas↗
arXiv2012

Thermodynamical properties of a trapped interacting Bose gas

The thermodynamical properties of interacting Bose atoms in a harmonic potential are studied within the mean-field approximation. For weak interactions, the quantum statistics is equivalent to an ideal gas in an effective mean-field potential. The eigenvalue of the Gross-Pitaevskii equation is identified as the chemical potential of the ideal gas. The condensation temperature and density profile of atoms are calculated. It is found that the critical temperature $T_c$ decreases as the interactions increase. Below the critical point, the condensation fraction exhibits a universal relation of $N_0/N=1-(T/T_c)^γ$, with the index $γ\approx 2.3$ independent of the interaction strength, the chemical potential, as well as the frequency of the confining potential.

cond-mat.quant-gas↗
arXiv2011

Fermionic superfluidity and spontaneous superflows in optical lattices

We study superfluidity of strongly repulsive fermionic atoms in optical lattices. The atoms are paired up through a correlated tunneling mechanism, which induces superfluidity when repulsive nearest-neighbor interactions are included in the Hubbard model. This paired superfluid is a metastable state which persists for a long time as the pair-broken process is severely suppressed. The mean-field phase diagram and low energy excitations are investigated in a square lattice system. Intriguingly, spontaneous superflows may appear in the ground state of a triangular optical lattice system due to antiferromagnetic frustration.

cond-mat.quant-gas↗