Eur. Phys. J. B (2018) 91: 203
https://doi.org/10.1140/epjb/e2018-90352-9

Regular Article

Exact ground states of the extended Hubbard model on the Kagomé lattice^★

¹ Department of Physics, Ehime University Bunkyo-cho 2-5, Matsuyama, Ehime 790-8577, Japan
² Department of Physics, Technical University Dresden, 01069 Dresden, Germany
³ Institute for Theoretical Solid State Physics, IFW Dresden, 01171 Dresden, Germany

^a e-mail: nakamura.masaaki.dq@ehime-u.ac.jp
^b e-mail: s.nishimoto@ifw-dresden.de

Received: 14 July 2017
Published online: 17 September 2018

Abstract

We discuss the exact plaquette-ordered ground states of the generalized Hubbard model on the Kagomé lattice for several fillings, by constructing the Hamiltonian as a sum of products of projection operators for up and down spin sectors. The obtained exact ground states are interpreted as Néel ordered states on the bond-located electrons. We determine several parameter regions of the exact ground states, and calculate the entanglement entropy. We examine the above results by numerical calculations based on exact diagonalization and density-matrix renormalization group methods.