Nano-pattern induced ferromagnetism in strongly correlated electrons

TL;DR

This theoretical study explores how nano-patterning in strongly correlated electron systems induces complex ferromagnetic phases, revealing high sensitivity to parameters and demonstrating the effectiveness of Hartree-Fock methods for large-scale simulations.

Contribution

It introduces a detailed analysis of ferromagnetism in nano-patterned lattices, showing the accuracy of Hartree-Fock methods and predicting rich phase diagrams in such systems.

Findings

Unconventional ferromagnetic phase diagrams with multiple transitions.

High accuracy of Hartree-Fock compared to Exact Diagonalization.

Nano-patterned lattices as promising candidates for engineered ferromagnetism.

Abstract

Band ferromagnetism in strongly correlated electron systems is one of the most challenging issue 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 a near future.