Interacting bosons in two-dimensional flat band systems
1 Institut für Physik, University of
2 Institut für Theoretische Physik, University of Heidelberg, 69120 Heidelberg, Germany
Received in final form: 1 July 2015
Published online: 12 August 2015
The Hubbard model of bosons on two dimensional lattices with a lowest flat band is discussed. In these systems there is a critical density, where the ground state is known exactly and can be represented as a charge density wave. Above this critical filling, depending on the lattice structure and the interaction strength, the additional particles are either delocalised and condensate in the ground state, or they form pairs. Pairs occur at strong interactions, e.g., on the chequerboard lattice. The general mechanism behind this phenomenon is discussed.
Key words: Solid State and Materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2015