Phase diagram of the Bose-Hubbard model on a ring-shaped lattice with   tunable weak links
  Motivated by recent experiments on toroidal Bose-Einstein condensates in all-optical traps with tunable weak links, we study the one-dimensional Bose-Hubbard model on a ring-shaped lattice with a small region of weak hopping integrals using quantum Monte Carlo simulations. Besides the usual Mott insulating and superfluid phases, we find a phase which is compressible but non superfluid with a local Mott region. This `local Mott' phase extends in a large region of the phase diagram. These results suggest that the insulating and conducting phases can be tuned by a local parameter which may provide a new insight to the design of atomtronic devices. 
Kalani Hettiarachchilage, Val\'ery G. Rousseau, Ka-Ming Tam, Mark   Jarrell, Juana Moreno
cond-mat.quant-gas