Finite Temperature Phase Diagram of the Disordered Extended Bose-Hubbard Model

Qi Zhou, Yasuyuki Kato, Naoki Kawashima +1 more

Philip Russ, Laura Wadleigh, Brian DeMarco

Fei Lin, T. A. Maier, V. W. Scarola

The extended Bose-Hubbard model captures the essential properties of a wide variety of physical systems including ultracold atoms and molecules in optical lattices, Josephson junction arrays, and certain narrow band superconductors. It exhibits a rich phase diagram including a supersolid phase where a lattice solid coexists with a superfluid. We use quantum Monte Carlo to study the supersolid part of the phase diagram of the extended Bose-Hubbard model on the simple cubic lattice. We add disorder to the extended Bose-Hubbard model and find that the maximum critical temperature for the supersolid phase tends to be suppressed by disorder. But we also find a narrow parameter window in which the supersolid critical temperature is enhanced by disorder. Our results show that supersolids survive a moderate amount of spatial disorder and thermal fluctuations in the simple cubic lattice.

Madhumita Kabiraj, Raka Dasgupta

We investigate the thermal melting of the incompressible lobes in the extended Bose-Hubbard model for both pure and disordered systems, motivated by recent experimental realizations using ultracold Rydberg atoms in optical lattices. By tuning the Rydberg excitation level and the lattice spacing, one can engineer the system to effectively have (i) only the nearest-neighbor (NN) interaction or (ii) NN and next-NN interactions. For both these schemes, we employ a mean-field framework to map out the finite-temperature phase diagrams. It is observed that the conventional Mott-insulating and density-wave lobes gradually transform into a normal fluid with increasing temperature. The melting temperature of the Mott lobes is controlled by the on-site interaction, while that of the density-wave lobes is governed by its NN counterpart. We also observe that the inclusion of disorder lowers the melting temperatures of both these insulating phases. The additional Bose-glass phase that appears in the presence of disorder, however, does not vanish at higher temperatures. Instead, it starts occupying a larger area in the phase diagram. The formalism that we present here is capable of treating long-range interactions, disorder, and finite temperature all at once. Moreover, it is versatile enough so that it can be extended to study other forms of disorder, and also be tailored to include longer-range interactions.

G. Migliorini, A. Nihat Berker

Yuanyu Zhang, Jihong Qin, Junjun Xu