Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Spins on Surfaces at the Atomic Scale I

O 59.10: Talk

Wednesday, March 19, 2025, 12:45–13:00, H6

A quantum simulator to study electronic structure of matter in the Hofstadter limit — •Hermann Osterhage, Julian H. Strik, Kira Junghans, Niels P. E. van Mullekom, Anna M. H. Krieg, Emil Sierda, Danis Badrtdinov, Daniel Wegner, Mikhail I. Katsnelson, Malte Rösner, and Alexander A. Khajetoorians — Radboud University, Nijmegen, The Netherlands

The Hofstadter limit describes electronic structure in strong magnetic fields, where the magnetic length is on the order of the periodicity of the crystal. In this limit, the electronic structure shows self-similarity, namely fractal behavior. Experimentally, it is challenging to reach this limit for conventional crystals due to the high required field strengths. Therefore, one solution is to investigate structures with effectively larger periodicities. [1]. However, finding platforms that allow to study this limit with control over orbital and lattice symmetries is a current challenge.

Here, I will present a quantum simulator based on patterning Cs atoms on the surface of InSb(110) by scanning tunneling microscopy [2]. Cs atoms can be patterned into nanostructures that exhibit multi-orbital wavefunctions reminiscent of an artificial atom, and can be coupled to each other. We detail how the electronic spectrum evolves in magnetic field, and discuss the role of finite size effects and temperature, as well as link this to the expected spectra in the Hofstadter limit.
[1] R. Krishna Kumar et al., Science 357, 181 (2017).
[2] E. Sierda, et al, Science 380, 1048 (2023).

Keywords: 2D electron system; semiconductor; STM; artificial lattices; Landau quantization