Coherent Transportation Properties In The Ultracold Atoms

Recently, the studies of manipulating ultracold atoms by lasers have attracted some attentions in modern physics. Because of quantum tunneling, a particle trapped in a double-well potential can not be located in the one of the two-well for long time. But if the double-well potential is driven by an external periodic force, the quantum tunneling can be suppressed, which results in the particle being located in one of well of double-well potential, it is known as the coherent destruction of tunneling. However, the researches of coherent destruction of tunneling are limited in the system only with short range contacted interaction, and manipulating cold atoms with single spin. Hence, in this paper, we investigate the transportation properties of Bose gas with both short-range contacted and long range dipole-dipole interactions under the different modulations. In particular, we propose a scheme for accurately controlling spin transportation for spinor Bose gas. The specific contents and conclusions of this paper are as follows:In the first chapter, the physical background and the related physical knowledge are briefly introduced, including coherent destruction of tunneling, dipolar Bose gas, and spin-orbit coupling Bose gas.In the second chapter, within the mean-field three-site Bose-Hubbard model, the tunneling dynamics of dipolar bosonic gas with repulsive interactions in a periodically driven triple-well are investigated. We find that, in a dipolar system, because of the coupled effect of long-range dipolar interaction (DDI) and short-range on-site interaction, the system experiences rich coherent tunneling (CT)-coherent destruction of tunneling (CDT) transition. In particular, as the atomic interaction increases, the system can un-dergo CT-CDT-CT-CDT or CDT-CT-CDT-CT-CDT transitions. This can not occur in non-dipolar gas. By high-frequency approximation, we find that, because of the atomic interactions, the emergence of complex loop structures in quasi-energies spectrum re-sults in the quasi-energies crossing and anti-crossings, which induces CDT. Interestingly, the coupling between the DDI and the on-site interaction modifies the properties of the energies spectrum and CT-CDT transitions significantly. CDT occurs only at isolated quasi-energies crossing points when the DDI and the on-site interaction have satisfied some relationship, which is similar to the case of a driven linear system.In the third chapter, within the mean-field three-site Bose-Hubbard model, the tun-neling dynamics of dipolar bosonic gas with a periodically modulation of s-wave scatter-ing is investigated. The system can experience complex and rich CT-CDT transitions resulting from the correlated effect among DDI, the on-site interaction and the modu-lated s-wave scattering. In particular. The region of the modulated s-wave scattering for generating CT(CDT) is the widest (narrowest) when the on-site interaction and the next-neighbor DDI have some correlated values, which are closely related to the tunneling energy and the interaction energy of the system. The correlated values for appearing CDT can be theoretically gained from the tunneling energy and the interaction energy of the system.In the fourth chapter, we theoretically propose a scheme for realizing selective coher-ent spin transportation in spin-orbit coupled bosonic gas trapped in a symmetric double-well by fast modulation of the energy level unbalance between the two wells. The modu-lation can be tuned in such a way that an arbitrarily, a priori prescribed spin type (single spin, or a spin-pair with opposite spins) and the number of these spin bosons with or without spin-flipping are allowed to tunnel. Furthermore, prescribed superexchange of spin bosons (with only pure spin exchange between the two wells and the atom number in each well is not changed) is also presented.Finally, we summarize the main results and give an outlook of the future in this field.