Heidelberg 2015 – wissenschaftliches Programm
Q 12.6: Vortrag
Montag, 23. März 2015, 15:45–16:00, P/H2
Ground states for the Bose-Hubbard model with flat bands — •Petra Pudleiner1 and Andreas Mielke2 — 1Institute of Physics, Johannes Gutenberg University, Mainz, Germany — 2Institute for Theoretical Physics, Ruprecht-Karls University, Heidelberg, Germany
Flat band systems have been studied intensively in experiment and theory. They are a prototype for strongly correlated systems. Especially for bosons in a flat band, several interesting questions arise: What is the nature of the ground state? Are there regions in phase space where one can see a Bose transition?
The Bose-Hubbard model is used to visualize low energies on two-dimensional lattices which exhibit a lowest flat energy band. Up to the critical lattice filling constant, an eigenstate of the aforementioned band can be constructed by means of the charge density wave (CDW) as many-body ground state. Huber and Altman  explored ground states in the vicinity of the critical filling on the kagome lattice via a mean-field calculation; however, by restricting the calculation to a weakly interacting Hamiltonian.
The purpose of this talk is, firstly, to present similar results which are obtained by transferring their methods to the checkerboard lattice and, secondly, to demonstrate initial steps to extend to strong interactions. In this regard, one boson is added to the well-known ground state. The distribution of this additional particle seems to be localized, in contrast to the weakly interacting limit; here we observe a Bose condensation.
 S. Huber and E. Altman, PRB 82, 184502 (2010)