Determination of Realistic Effective Models for Weyl Semimetals of the TaAs Family

Topological quantum materials have many novel properties that make them interesting for use in future spintronic computing devices. However, calculating and predicting the electronic properties of actual spintronic computing devices is proving difficult because, due to their use at the micro- and nanoscale, they have complex geometries and are often composed of many different components. As a result, density functional theory calculations of the band structure are very time-consuming and resource-intensive.<br /> Effective low-energy models offer the possibility of simplifying and accelerating the calculations. For example, they can serve as a starting point for the derivation of tight-binding models in which only hopping processes between neighboring atoms are taken into account. The challenge is to calculate suitable effective low-energy models that can realistically represent the physical and electronic properties of a material.<br /> This thesis focuses on two different classes of topological quantum materials: topological insulators with the material family Bi2Se3 and Weyl semimetals with the material family TaAs as concrete application examples. After a detailed introduction into the peculiarities of topological quantum materials, the essential physical properties of topological insulators and Weyl semimetals are described. Two different methods for the calculation of effective low-energy models are then presented: the 𝑘 ⋅ 𝑝 theory and the fit method. Both methods are based on a model Hamiltonian operator derived from the symmetries of the respective crystal lattice. Concrete low-energy models are then calculated for the various example materials. The aim of the methods is to qualitatively and quantitatively map the essential topological properties of the materials in a simplified model so that they can later be used, for example, to calculate concrete tight-binding models and spintronic computer devices.<br /> The thesis concludes with a brief summary of the project results and an outlook on further research activities that may result from this work.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bielefeld

Year

2024

Author dc:creator

• Wenz, Kai

Repository record source_url

https://pub.uni-bielefeld.de/record/3000327

OAI identifier oai:identifier

oai:pub.uni-bielefeld.de:3000327