From Electronic Structure to Charge-, Spin- and Polaron-Transport

The number of materials is exploding and completely new material classes are emerging that were unknown a few years ago, including topological insulators, Weyl semimetals, 2D materials and novel organic semiconductors. For such emerging materials, electronic structure approaches (such as density function theory or many-body perturbation theory) can describe electronic properties, which can be directly compared with measurements from angle-resolved photoelectron spectroscopy or probed locally by scanning tunneling spectroscopy. Understanding electron transfer and charge transport properties, however, is often more complicated. This is because – in addition to the electronic properties – it requires describing disorder, vibrations or other perturbations that are less visible to spectroscopic probes. In addition, typical transport geometries require the simulation of large systems, since the transport properties depend on the size of the system. Unfortunately, current tools either suffer from a lack of accuracy or scale badly with the system size. In this presentation, I will introduce linear-scaling approaches that aim at closing this gap. For selected cases, I will demonstrate how large-scale charge-transport and spin-transport simulations based on the Kubo framework in combination with electronic-structure simulations can lead to an in-depth understanding of various transport signatures that would otherwise remain unexplained.

Figure 1: Illustration of spin dependent transport in gold decorated graphene (left), the effective electrostatic potential of h-BN in a bilayer with graphene (middle) and the structure of an organic semiconductor blend (right).