Volume 91, Number 5, September 2010
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||24 September 2010|
Ferromagnetism in the Hubbard model with topological/non-topological flat bands
Kavli Institute for Theoretical Physics, University of California - Santa Barbara, CA 93106, USA
2 Cross-Correlated Materials Research Group (CMRG), ASI, RIKEN - Wako, Saitama 351-0198, Japan
3 Graduate School of Engineering Science, Osaka University - Toyonaka, Osaka 560-8531, Japan
4 Department of General Education, Ariake National College of Technology - Omuta, Fukuoka 836-8585, Japan
5 Department of Physics, Gakushuin University - Mejiro, Toshima-ku, Tokyo 171-8588, Japan
Accepted: 30 August 2010
We introduce and study two classes of Hubbard models with magnetic flux or with spin-orbit coupling, which have a flat lowest band separated from other bands by a non-zero gap. We study the Chern number of the flat bands, and find that it is zero for the first class but can be non-trivial in the second. We also prove that the introduction of on-site Coulomb repulsion leads to ferromagnetism in both the classes.
PACS: 71.10.Fd – Lattice fermion models (Hubbard model, etc.) / 71.10.-w – Theories and models of many-electron systems / 05.30.Fk – Fermion systems and electron gas
© EPLA, 2010
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