Magnetism Of Spinor Ultracold Bosons In Optical Lattices

Ultracold atoms trapped in an optical lattice offer a unique research arena in which physics of interacting quantum many-body systems can be explored with unprecedented controllability and precision.Ultracold atoms with spin degrees of freedom have attracted considerable interest due to the possibilities of simulating quantum magnetism and exploring the interplay between spatial and spin degrees of freedom.A model for studying such physics is the spin-1 Bose-Hubbard model,which describes spin-1 atoms in optical lattices.The model can be either ferromagnetic or antiferromagnetic,depending on the sign of the spin-dependent interaction.The theoretical studies on spin-1 ultracold bosons with antiferromagnetic interactions in optical lattices have drawn increasing attention.We investigate strongly correlated spin-1 ultracold bosons in a cubic optical lattice with conserved magnetism(uniform magnetic field),based on bosonic dynamical meanfield theory.Bosonic dynamical mean-field theory includes the local quantum fluctuations of the strongly correlated system,which can solve non-perturbative strongly correlated bosonic system.Phase diagrams of the system with antiferromagnetic interactions are mapped out at both zero and finite temperature.At zero temperature,when the intensity of the magnetic field is small,we demonstrate the existence of the spin-singlet insulator and ferromagnetic phase,with the increase of the intensity of the magnetic field,the transition of spin-singlet insulator phase into ferromagnetic phase is observed,in addition,for relatively large intensity of the magnetic field,all the insulating phases are turned into the ferromagnetic.When system's intensity of magnetic field is constant,with the increase of temperature,the transition of spin-singlet insulator phase into ferromagnetic phase and existence of normal state is observed.