Superfluid-Mott insulator transition in spin-orbit coupled Bose-Hubbard Model

Hitoshi Inoue

Владимир Федорович Елесин, V. А. Kashurnikov, L. А. Openov

Jize Zhao, Shijie Hu, Jun Chang +3 more

We study the evolution of magnetic structures driven by a synthetic spin-orbit coupling in a one-dimensional two-component Bose-Hubbard model. In addition to the Mott insulator-superfluid transition, in the Mott insulator phases we found a transition from a gapped ferromagnetic phase to a gapless chiral phase by increasing the strength of the spin-orbit coupling. Further increasing the spin-orbit coupling drives a transition from the gapless chiral phase to a gapped antiferromagnetic phase. These magnetic structures persist in superfluid phases. In particular, in the chiral Mott insulator and chiral superfluid phases, incommensurability is observed in characteristic correlation functions. These unconventional Mott insulator phase and superfluid phase demonstrate the different effects arising from the competition between the kinetic energy and the spin-orbit coupling.

Ahmet Tuna Bolukbasi, M. Iskin

We consider a square optical lattice in two dimensions and study the effects of both the strength and symmetry of spin-orbit coupling and Zeeman field on the ground-state, i.e., Mott-insulator (MI) and superfluid (SF), phases and phase diagram, i.e., MI-SF phase-transition boundary, of the two-component Bose-Hubbard model. In particular, based on a variational Gutzwiller ansatz, our numerical calculations show that the spin-orbit-coupled SF phase is a nonuniform (twisted) one, with its phase (but not the magnitude) of the order parameter modulating from site to site. Fully analytical insights into the numerical results are also given.

H. Yokoyama, T. Miyagawa, Masao Ogata

Manuel Endres