11,432 research outputs found
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
Merging GW with DMFT and non-local correlations beyond
We review recent developments in electronic structure calculations that go
beyond state-of-the-art methods such as density functional theory (DFT) and
dynamical mean field theory (DMFT). Specifically, we discuss the following
methods: GW as implemented in the Vienna {\it ab initio} simulation package
(VASP) with the self energy on the imaginary frequency axis, GW+DMFT, and ab
initio dynamical vertex approximation (DA). The latter includes the
physics of GW, DMFT and non-local correlations beyond, and allows for
calculating (quantum) critical exponents. We present results obtained by the
three methods with a focus on the benchmark material SrVO.Comment: tutorial review submitted to EPJ-ST (scientific report of research
unit FOR 1346); 11 figures 27 page
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