Double Exchange model for nanoscopic clusters

We solve the double exchange model on nanoscopic clusters exactly, and specifically consider a six-site benzene-like nanocluster. This simple model is an ideal testbed for studying magnetism in nanoclusters and for validating approximations such as the dynamical mean field theory (DMFT). Non-local correlations arise between neighboring localized spins due to the Hund's rule coupling, favoring a short-range magnetic order of ferro- or antiferromagnetic type. For a geometry with more neighboring sites or a sufficiently strong hybridization between leads and the nanocluster, these non-local correlations are less relevant, and DMFT can be applied reliably.Comment: 9 pages, 9 figures, 1 tabl

Projective Quantum Monte Carlo Method for the Anderson Impurity Model and its Application to Dynamical Mean Field Theory

We develop a projective quantum Monte Carlo algorithm of the Hirsch-Fye type for obtaining ground state properties of the Anderson impurity model. This method is employed to solve the self-consistency equations of dynamical mean field theory. It is shown that the approach converges rapidly to the ground state so that reliable zero-temperature results are obtained. As a first application, we study the Mott-Hubbard metal-insulator transition of the one-band Hubbard model, reconfirming the numerical renormalization group results.Comment: 4 pages, 4 figure