Eur. Phys. J. B (2014) 87: 143
https://doi.org/10.1140/epjb/e2014-50294-x

Regular Article

Interaction-created effective flat bands in conducting polymers

Department of Theoretical Physics, University of Debrecen, 4010 Debrecen, Hungary

^a e-mail: gulacsi@phys.unideb.hu

Received: 7 May 2014
Received in final form: 21 May 2014
Published online: 25 June 2014

Abstract

For a general class of conducting polymers with arbitrary large unit cell and different on-site Coulomb repulsion values on different type of sites, I demonstrate in exact terms the emergence possibility of an upper, interaction-created “effective” flat band. This last appears as a consequence of a kinetic energy quench accompanied by a strong interaction energy decrease, and leads to a non-saturated ferromagnetic state. This ordered state clearly differs from the known flat-band ferromagnetism. This is because it emerges in a system without bare flat bands, requires inhomogeneous on-site Coulomb repulsions values, and possesses non-zero lower interaction limits at the emergence of the ordered phase.