Valter L. Líbero

Impurity and boundary effects in one- and two-dimensional inhomogeneous Heisenberg antiferromagnets

We calculate the ground-state energy of one- and two-dimensional spatially inhomogeneous antiferromagnetic Heisenberg models for spins

Spin-distribution functionals and correlation energy of the Heisenberg model

1∕2

Simple model for coupled magnetic and quadrupolar instabilities in uranium heavy-fermion materials

, 1,

Magnetic susceptibility of a two-channel Anderson model

3∕2

Renormalization-group calculation of dynamical properties for impurity models

, and 2. Our calculations become possible as a consequence of the recent formulation of density-functional theory for Heisenberg models. The method is similar to spin-density-functional theory, but employs a local-density-type approximation designed specifically for the Heisenberg model, allowing us to explore parameter regimes that are hard to access by traditional methods, and to consider complications that are important specifically for nanomagnetic devices, such as the effects of impurities, finite size, and boundary geometry, in chains, ladders, and higher-dimensional systems.

Multi-step transformation in numerical renormalization group

We analyze the ground-state energy and correlation energy of the Heisenberg model as a function of spin, both in the ferromagnetic and the antiferromagnetic case, and in one, two and three dimensions. First, we present a comparative analysis of known expressions for the ground-state energy

Non-fermi liquid fixed points of a two-channel Anderson model

{E}_{0}(S)

Energy of bond defects in quantum spin chains obtained from local approximations and from exact diagonalization

of homogeneous Heisenberg models. In the one-dimensional antiferromagnetic case we propose an improved expression for

A aproximação de campo médio de Bethe-Peierls

{E}_{0}(S),

Renormalization of the tunneling rate between two centers in a metal

which takes into account Bethe-ansatz data for