arXiv subjects

Gernot Stollhoff

Publications and source records attributed to Gernot Stollhoff.

3 recordsLinked to original sources

arXiv2009

Multiband Hubbard Models and the Transition Metals

Correlation computations on multiband Hubbard Hamiltonians are presented. It is shown why the proper degeneracy is of vital importance and that the atomic exchange interaction plays a particular role. The different methods are connected, and their results are discussed. Many experimental properties for the elemental solids can be explained by single closely related sets of parameters each. There is an exception, Tc of Fe. Here, a novel feature of longer-range interactions enters, as demonstrated on ab-initio results of the Local Ansatz for Fe. Connections are made to LSDA-calculations; and their seeming successes and deficiencies are explained.

cond-mat.str-el↗

arXiv2002

Electron Correlations in the High Tc-Compounds

Ab-initio correlation results for an idealized high Tc-compound are compared to density functional (DF) calculations for the same system. It is shown that and why the DF-charge distribution is wrong. The largest deficiency arises for the Cu-d(x2-y2)-occupation, originating from strong atomic correlations but mostly from anomalous neighbor Cu-spin correlations. Both features are beyound the range of the homogeneous electron gas approximation underlying the DF-schemes. The ab-initio results also exclude a description of the real system in a Mott-Hubbard scenario, that is mostly chosen in theory.

cond-mat.supr-con↗

arXiv1998

Electrons in High-Tc Compounds: Ab-Initio Correlation Results

Electronic correlations in the ground state of an idealized infinite-layer high-Tc compound are computed using the ab-initio method of local ansatz. Comparisons are made with the local-density approximation (LDA) results, and the correlation functions are analyzed in detail. These correlation functions are used to determine the effective atomic-interaction parameters for model Hamiltonians. On the resulting model, doping dependencies of the relevant correlations are investigated. Aside from the expected strong atomic correlations, particular spin correlations arise. The dominating contribution is a strong nearest neighbor correlation that is Stoner-enhanced due to the closeness of the ground state to the magnetic phase. This feature depends moderately on doping, and is absent in a single-band Hubbard model. Our calculated spin correlation function is in good qualitative agreement with that determined from the neutron scattering experiments for a metal.

cond-mat.supr-con↗