Nano-pattern–induced ferromagnetism in strongly correlated electrons

¹ Institut Néel, UPR2940, CNRS et Université de Grenoble - Grenoble, F-38042 France, EU
² Jacobs University Bremen - Campus Ring 1, D-28759 Bremen, Germany, EU

Received: 19 September 2012
Accepted: 5 February 2013

Abstract

Band ferromagnetism in strongly correlated electron systems is one of the most challenging issues in today's condensed-matter physics. In this theoretical work, we study the competition between kinetic term, Coulomb repulsion, and on-site correlated disorder for various lattice geometries. Unconventional and complex ferromagnetic phase diagrams are obtained: wide region of stability, cascade of transitions, re-entrance, high sensitivity to the carrier concentration and strongly inhomogeneous ground states for relatively weak on-site potential. The direct and systematic comparison with exact diagonalization shows that the unrestricted Hartree-Fock method is unexpectedly accurate for such systems, which allows large-size cluster calculations. A match of the order of 99.9% for weak and intermediate couplings is found, slightly reduced to about 95% in the large-repulsion regime. Nano-patterned lattices appear to be particularly promising candidates that could, with the tremendous progress in growing and self-organized techniques, be synthesized in the near future.