We study the ground-state phases of a two-dimensional rotating spin-orbit–coupled Bose-Einstein condensate loaded in a one-dimensional spin-dependent optical lattice. In the absence of rotation, the system undergoes a phase transition from the stripe phase to the supersolid phase gradually for weak spin-orbit coupling strength and directly for strong spin-orbit coupling strength as the depth of the optical lattice increases. With increasing the rotation strength, the stripe phase transforms to the ringlike state, and the domain number of the ringlike state increases when the Bose-Einstein condensate is in the weak depth of the optical lattice. The supersolid phase transforms to the phase with a single domain of a vortex line for small rotation strength, and alternating vortex lines along the x -direction appear for large rotation strength when the Bose-Einstein condensate is in the strong depth of the optical lattice. The spin textures of the ground-state phases are also discussed.
We discuss the structure of spin-1 Bose-Einstein condensates in the presence of a homogenous magnetic field. We demonstrate that phase separation can occur in the ground state of antiferromagnetic (polar) condensates, while the spin components of ferromagnetic condensates are always miscible, so that no phase separation occurs in them. Our analysis predicts that this phenomenon takes place when the energy of the lowest homogenous state is a concave function of the magnetization. We propose a method for creating spin domains by adiabatic switching-on of a magnetic field. We also discuss the phenomena of dynamical instability and spin domain formation.
In spinor Bose Einstein condensates (BEC) gases, a fraction of its thermally excited atoms can still interact with the condensate ground state, leading to spin-spin interactions that can modify the main features of its spin-phase diagrams. In this work we study the spin-phase diagram of a BEC of general spin-
f and fully characterize its noncondensate thermal fraction. The latter provided that the condensate ground state lies within a spin phase with rotational symmetry. The study is based in the Hartree-Fock approximation in conjunction with the Majorana stellar representation approach for pure and mixed quantum states and the use of point-group symmetry arguments. The method allows us to study the phase diagram of spinorial BECs with usual point-group symmetries, including those with some exotic phases associated to the platonic solids (
f=2,3,4, and 6), which are known to lead to non-Abelian topological excitations. In addition, we explore the temperature effects on the admissible spin-phase domains for general spin values, as well as its physical implications on their multipolar magnetic moments.