The quantum self-trapping phenomenon of a Bose-Einstein condensate (BEC) represents a remarkable nonlinear effect of wide interest. By considering a purely dipolar BEC in a double-well potential, we study how the dipole orientation affects the ground state structure and the transition between self-trapping and Josephson oscillation in dynamics. Three-dimensional numerical results and an effective two-mode model demonstrate that the onset of self-trapping of a dipolar BEC can be radically modified by the dipole orientation. We also analyze the failure of the two-mode model in predicting the rate of Josephson oscillations. We hope that our results can motivate experimental work as well as future studies of self-trapping of ultracold dipolar gases in optical lattices.

Under a unified theory we investigate the formation of various types of vector-solitons in twospecies Bose-Einstein condensates with arbitrary scattering lengths. We then show that by tuning the interaction parameter via Feshbach resonance, transformation between different types of vector solitons is possible. Our results open up new ways in the quantum control of multi-species Bose-Einstein condensates.

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The adsorption behavior of adsorbents for carbon dioxide can be significantly affected by flue gas contaminants. In this work, we examined the performance of tetraethylenepentamine (TEPA) impregnated industrial grade multiwalled carbon nanotubes (IG-MWCNTs) in trace amounts of flue gas contaminants such as H2O, NO, and SO2. It was observed that H2O and NO had a minimal impact on CO2 adsorption capacity, while the effect of SO2 on CO2 adsorption was influenced by adsorption temperature and SO2 concentration. Compared with silica-based adsorbents, i.e., TEPA-impregnated MCM-41, amine-functionalized IG-MWCNTs show significantly better tolerance to H2O and SO2. In addition, we examined the variation of CO2 adsorption with and without SO2 with various experimental methods (N2 adsorption/desorption isotherms, X-ray diffraction, and differential scanning calorimetry analysis) and molecular simulation. Experimental results show that irreversible sulfate/sulphite species deposited into the adsorbent contributes to the decrease on CO2 adsorption, while the results from simulation studies reveal that the enthalpy difference between the isolated TEPA with SO2 and TEPA···SO2 (ΔH(TEPA···SO2)) is larger than that of CO2 (ΔH(TEPA···CO2)), indicating that SO2 has a stronger reaction activity with TEPA than CO2. The increase of the ratio of ΔH(TEPA···SO2)/ΔH(TEPA···CO2) with increasing temperature illustrates that the difference of CO2 adsorption capacity with and without SO2 increases with elevated temperatures.

We present theoretical analysis and numerical studies of the quantized vortices in a rotating Bose-Einstein condensate with spatiotemporally modulated interaction in harmonic and anharmonic potentials, respectively. The exact quantized vortex and giant vortex solutions are constructed explicitly by similarity transformation. Their stability behavior has been examined by numerical simulation, which shows that a new series of stable vortex states (defined by radial and angular quantum numbers) can be supported by the spatiotemporally modulated interaction in this system. We find that there exist stable quantized vortices with large topological charges in repulsive condensates with spatiotemporally modulated interaction. We also give an experimental protocol to observe these vortex states in future experiments.

We investigate the way in which the pattern of fringes in a coherent pair of two-dimensional Bose condensed clouds of ultra-cold atoms traveling in opposite directions subject to a harmonic trapping potential can seed the irreversible formation of internal excitations in the clouds, notably solitons and vortices. We identify under, over and critically damped regimes in the dipole oscillations of the condensates according to the balance of internal and centre-of-mass energies of the clouds. We carry out simulations of the collision of two clouds with respect to different initial phase differences in these regimes to investigate the creation of internal excitations. We distinguish the behaviour of this system from previous studies of quasi one-dimensional BEC's. In particular we note that the nature of the internal excitations is only essentially sensitive to an initial phase difference between the clouds in the overdamped regime.

We systematically investigate the topological superfluidity of a Rydberg-dressed Fermi gas, where the soft-core effective interaction is of finite radius R c due to the blockade effect. We calculate the quantum phase diagram within the mean-field approximation and find three distinct phases: polar (p z ), axial (p x + ip y ), and axiplanar (p x + iβ p p y ) phases. The tricritical point is around R c k F ∼ 1, where k F is the Fermi wave vector. We further derive the Ginzburg-Landau theory to explain the phase diagram and estimate the transition temperature to be about 0.1E F in the current experimental regime of 6 Li. Our work paves the way for future studies on exotic topological superfluids and related quantum phase transitions.

We systematically investigate the ground state and elementary excitations of a Bose-Einstein Condensate within a synthetic vector potential, which is induced by the many-body effects and atomlight coupling. For a sufficiently strong inter-atom interaction, we find the condensate undergoes a Stoner-type ferromagnetic transition through the self-consistent coupling with the vector potential. For a weak interaction, the critical velocity of a supercurrent is found anisotropic due to the density fluctuations affecting the gauge field. We further analytically demonstrate the topological ground state with a coreless vortex ring in a 3D harmonic trap and a coreless vortex-antivortex pair in a 2D trap. The circulating persistent current is measurable in the time-of-flight experiment or in the dipolar oscillation through the violation of Kohn theorem.Introduction: Gauge fields play an important role in the modern particle physics, mediating interaction between elementary particles. In condensed matter physics, the gauge fields bring many important phenomena, such as integer/factional quantum Hall effects[1, 2], Laughlin liquids [3] and Hofstadter butterfly spectrum[4], etc. In quantum gas systems, artificial gauge fields can be also generated for neutral atoms in the rotating frame [5,6], or by the atom-light coupling with spatial dependent laser fields [7][8][9] or detuning [10,11]. The latter opens up a new possibility to study many-body physics with gauge potential, and is extended to investigate the spin-orbital coupling problems in similar experiments [12].Besides of the generating by external lasers, it was theoretically proposed that the gauge field can be induced by dipole-dipole interaction between two dipolar or Rydberg atoms [13][14][15]. For many-body systems, some interesting dynamics [16] and excitations[17] within a densitydependent gauge field were investigated in a 1D system. However, considering the finite temperature effects and quantum fluctuations, it is certainly more realistic and demanding to investigate many-body properties in higher dimensional systems, where the effective gauge field may further introduce topological defects and more interesting many-body physics not observable in 1D systems.In this Letter, we systematically investigate the ground state and excitation properties of a (pseudo) spin-1/2 condensate with the interaction-induced gauge field in 2D and 3D systems. We find several new many-body properties: (i) For a sufficiently strong inter-atom interaction, the condensate can have a Stoner-type ferromagnetism through the self-consistent coupling with the synthetic field. (ii) In the weak interaction limit, we calculate the Bogoliubov excitation spectrum of a superfluid current, and show that the critical velocity for dynamical instability becomes anisotropic in space due to density fluctuations within the gauge field. (iii) In a harmonic trap, we show analytic solutions of the condensate ground state, and find a coreless vortex ring around the gauge field