4 research outputs found
Correlated electrons in the presence of disorder
Several new aspects of the subtle interplay between electronic correlations
and disorder are reviewed. First, the dynamical mean-field theory
(DMFT)together with the geometrically averaged ("typical") local density of
states is employed to compute the ground state phase diagram of the
Anderson-Hubbard model at half-filling. This non-perturbative approach is
sensitive to Anderson localization on the one-particle level and hence can
detect correlated metallic, Mott insulating and Anderson insulating phases and
can also describe the competition between Anderson localization and
antiferromagnetism. Second, we investigate the effect of binary alloy disorder
on ferromagnetism in materials with -electrons described by the periodic
Anderson model. A drastic enhancement of the Curie temperature caused by
an increase of the local -moments in the presence of disordered conduction
electrons is discovered and explained.Comment: 17 pages, 7 figures, final version, typos corrected, references
updated, submitted to Eur. Phys. J. for publication in the Special Topics
volume "Cooperative Phenomena in Solids: Metal-Insulator Transitions and
Ordering of Microscopic Degrees of Freedom
Magnetic properties of the three-dimensional Hubbard model at half filling
We study the magnetic properties of the 3d Hubbard model at half-filling in
the TPSC formalism, previously developed for the 2d model. We focus on the
N\'eel transition approached from the disordered side and on the paramagnetic
phase. We find a very good quantitative agreement with Dynamical Mean-Field
results for the isotropic 3d model. Calculations on finite size lattices also
provide satisfactory comparisons with Monte Carlo results up to the
intermediate coupling regime. We point out a qualitative difference between the
isotropic 3d case, and the 2d or anisotropic 3d cases for the double occupation
factor. Even for this local correlation function, 2d or anisotropic 3d cases
are out of reach of DMF: this comes from the inability of DMF to account for
antiferromagnetic fluctuations, which are crucial.Comment: RevTex, 9 pages +10 figure
Interplay between disorder and electron interactions Theoretical studies of an Anderson-Hubbard model
SIGLEAvailable from British Library Document Supply Centre- DSC:D180029 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
Rigorous Results, Cross-Model Justification, and the Transfer of Empirical Warrant: The Case of Many-Body Models in Physics
This paper argues that a successful philosophical analysis of models and simulations must accommodate an account of mathematically rigorous results. Such rigorous results may be thought of as genuinely model-specific contributions, which can neither be deduced from fundamental theory nor inferred from empirical data. Rigorous results provide new indirect ways of assessing the success of models and simulations and are crucial to understanding the connections between different models. This is most obvious in cases where rigorous results map different models on to one another. Not only does this put constraints on the extent to which performance in specific empirical contexts may be regarded as the main touchstone of success in scientific modelling, it also allows for the transfer of warrant across different models. Mathematically rigorous results can thus come to be seen as not only strengthening the cohesion between scientific strategies of modelling and simulation, but also as offering new ways of indirect confirmation