BEC In Optical Lattice And Domain Wall And Domain Structure In Ferromagnetic Film

Bose-Einstein condensation in dilute atomic gas and quantum tunneling of magnetization vector in magnetic systems are both typical macroscopic quantum phenomena. This paper is mainly devoted to the theoretical investigation of thus two systems.Firstly, the macroscopic quantum state of the quasi-one-dimensional Bose-Einstein condensates in an optical lattice is obtained by solving the periodic Gross-Pitaevskii equation within the mean field theory. The resulting persistent atom current can be controlled by adjusting of the barrier height of the periodic potential. A critical condition to generate the persistent atom current is demonstrated and we moreover propose a practical experiment to realize the persistent atom current in a toroidal atom waveguide.Secondly, The exact macroscopic wave functions of two-species quasi-one-dimensional Bose-Einstein condensates in an optical lattice beyond the tight-binding approximation are studied by solving the coupled Gross-Pitaevskii equations. Phase diagram for the superfluid and insulator phases is determined according to the macroscopic wave functions of the condensates.Next, the low-energy spin-domain excitations of spinor BEC confined in a one-dimensional optical lattice are studied in terms of the equation of...