Superconducting Fluctuations in a Tight Binding Bandstructure

通过准粒子干涉洞察能带结构与库仑相互作用之间的相互影响

Insight into interplay between bandstructure and Coulomb interaction via quasiparticle interference

本文以铁基磷化物的金属自旋密度波态为例，证明准粒子干涉可作为探针揭示电子能带结构与关联效应间的相互影响，并据此缩小相互作用参数窗口以选择更现实的紧束缚模型。

Ferromagnetic superconductivity driven by changing Fermi surface topology

We introduce a simple but powerful zero temperature Stoner model to explain the unusual phase diagram of the ferromagnetic superconductor, UGe2. Triplet superconductivity is driven in the ferromagnetic phase by tuning the majority spin Fermi level through one of two peaks in the paramagnetic density of states (DOS). Each peak is associated with a metamagnetic jump in magnetisation. The twin peak DOS may be derived from a tight-binding, quasi-one-dimensional bandstructure, inspired by previous bandstructure calculations.

Numerical Study of Pseudo-gap Anisotropy for a Tight Binding Band

The Fermi surface anisotropy of a pseudo-gap in the spectral weight, caused by superconducting fluctuations or anti-ferromagnetic fluctuations, is calculated for a tight binding band. The importance of the Fermi surface saddle point, or hot spot, is illustrated. A peak-dip-hump structure due to a finite frequency mode, is briefly explored. The connection to high temperature superconducting copper-oxides is discussed.

Precise Tight-binding Description of the Band Structure of MgB2

We present a careful recasting of first-principles band structure calculations for MgB2 in a non-orthogonal sp-tight-binding (TB) basis. Our TB results almost exactly reproduce our full potential linearized augmented plane wave results for the energy bands, the densities of states and the total energies. Our procedure generates transferable Slater-Koster parameters which should be useful for other studies of this important material.

Tight-binding models for the new iron based superconductor materials

The rich novel materials class of iron based superconductors turned out to exhibit a very complex electronic structure, despite of the simplicity of their crystal structures. For various approaches to study the instability against magnetic order or superconductivity, a real space description of the electronic structure is required. Here, the bonding situation and the orbital structure of the electronic state are analyzed and minimum tight-binding models quantitatively correctly describing the low-energy electronic structure are provided.

A Tight-Binding Investigation of the NaxCoO2 Fermi Surface

We perform an orthogonal basis tight binding fit to an LAPW calculation of paramagnetic Na$_x$CoO$_2$ for several dopings. The optimal position of the apical oxygen at each doping is resolved, revealing a non-trivial dependence of the band structure and Fermi surface on oxygen height. We find that the small e$_{g'}$ hole pockets are preserved throughout all investigated dopings and discuss some possible reasons for the lack of experimental evidence for these Fermi sheets.