# Dresden 2020 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 39: Correlation Theory II

### MA 39.4: Vortrag

### Mittwoch, 18. März 2020, 15:45–16:00, HSZ 403

**Quantum Electrodynamical Bloch Theory with Homogeneous Magnetic Fields** — •Vasil Rokaj, Markus Penz, Michael Sentef, Michael Ruggenthaler, and Angel Rubio — Max Planck Institute for the Structure & Dynamics of Matter, Hamburg, Germany

Probing electronic properties of periodic systems by homogeneous magnetic fields has unravelled fundamental new phenomena in condensed matter physics. Much theoretical work has been devoted to describe those systems in different regimes, still a general first principles modeling of such fundamental effects is lacking. Here we propose a solution to the problem of Bloch electrons in a homogeneous magnetic field by including the quantum fluctuations of the photon field. A generalized quantum electrodynamical (QED) Bloch theory from first principles is presented. As an application, we show how the well-known Landau physics is modified by the photon field and that Landau polaritons emerge. Moreover, for a 2D solid in a perpendicular magnetic field, in the limit of vanishing quantum fluctuations, we recover the standard results of solid-state physics: the fractal spectrum of the Hofstadter butterfly. Further generalizations and modifications of the Hofstadter butterfly will be presented for 2D materials like graphene and Moire superlattices which are of current experimental interest.

[1]V.Rokaj et al. Phys. Rev. Lett. 123, 047202 (2019)