Title of the project: Electron-Phonon Coupling: From First Principles to Model Hamiltonians
Name of the VDSP student: Thomas Hahn
Project supervised by: Cesare Franchini

I am a PhD student in the Computational Material Physics group under the supervision of Univ.-Prof. Dr. techn. Cesare Franchini. We recently moved our offices to the new University building at Kolingasse 14-16. Currently I am in the third year of my PhD studies and my research interests include polarons and electron-phonon interactions as well as the development and implementation of numerical methods to study these kind of systems.

The image shows a Feynman diagram of an electron interacting with a phonon. It can be interpreted as an electron in state (n,k) traveling freely, without interaction, from time 0 to time t’. There it interacts with a phonon in state (q,v) and gets scattered into state (m,k-q). At time t’’, the electron interacts again with the phonon and gets scattered back into its original state (n,k). One encounters such Feynman diagrams when dealing with polarons. A polaron is a quasiparticle which forms due to the interaction between an electron and phonons in a crystal. My research focuses on the study of different polaron models with the Diagrammatic Monte Carlo (DMC) technique. We also try to combine first-principle calculations with effective polaron models and DMC. This could lead to a full ab-initio treatment of polarons in real materials.

Franchini group