Spin-1 bosons in an external magnetic field and a three body interaction   potential
  We perform a thorough study of the effect of an external magnetic field on a spin-1 ultracold Bose gas via mean field approach corresponding to the both signs of the spin dependent interaction. In contrast to some of the earlier studies, the magnetic field in our work is included through both the hopping frequencies (via Peierls coupling) and the zeeman interaction, thereby facilitating an explo- ration for competition between the two. The phase diagrams in the antiferromagnetic case shows that the Mott insulating (MI) phase with even particle occupancies is stable at low magnetic fields. At higher magnetic fields, due to a competition between the hopping and the zeeman interaction terms, the latter tries to destabilize the MI phase by suppressing the formation of singlet pairs, while the former tends to stabilize the MI phase. In the ferromagnetic case, the MI lobes become more stable with increasing flux strengths. Further inclusion of a three body interaction potential in order to ascertain its role on the phase diagram, we found that in absence of the magnetic field, the MI lobes become more stable compared to the superfluid (SF) phase and the location of the transition point for the MI-SF phase increases with increasing the three body interaction strength. A strong coupling perturbative calculation has also been done to provide a comparison with our mean field phase diagrams. Lastly, with inclusion of the external field, the insulating phases are found to be further stabilized by the three body interaction potential. 
Sk Noor Nabi and Saurabh Basu
cond-mat.quant-gas