Takahiro Ohgoe, Takafumi Suzuki, Naoki Kawashima
We investigate the hard-core Bose-Hubbard model with {\it fully anisotropic} long-range dipole-dipole interactions on square lattices. In our model, we assume that the dipole moments are oriented along a particular axis on the 2D plane. To treat this model exactly, we perform unbiased quantum Monte Carlo simulations using a hybrid algorithm of the worm algorithm and an O(N) Monte Carlo method. We obtain the ground-state phase diagram that includes a superfluid phase and a striped solid phase at the particle density $\rho=1/2$ in broad regions. The obtained phase diagram indicates that a supersolid state is unstable. We give the qualitative discussion of the reason from a perturbative treatment. Finite-temperature transitions to the phases are also investigated. For large dipole-dipole interactions, we observe a small $\rho = 1/3$ striped solid phase and incompressible regions adjacent to it. In spite of its incompressibility, the particle density increases as the chemical potential increases in the regions. This indicates the devil's staircase caused by the presence of numerous metastable states.
View original:
http://arxiv.org/abs/1110.2109
No comments:
Post a Comment