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O: Fachverband Oberflächenphysik
O 23: Ultrafast Electron Dynamics at Surfaces and Interfaces III
O 23.2: Talk
Tuesday, March 19, 2024, 10:45–11:00, MA 041
The challenge of realizing Floquet effects in epitaxial graphene — •Leonard Weigl1, Niklas Hofmann1, Johannes Gradl1, Peter Richter2, Thomas Seyller2, and Isabella Gierz1 — 1University of Regensburg — 2Technische Universität Chemnitz
Floquet engineering where the band structure of a solid is modified by periodic driving with strong laser pulses is a promising method for tailoring the electronic properties of solids on ultrafast time scales. One particularly tempting proposal is the opening of a topologically non-trivial gap in the Dirac cone of graphene with circularly polarized light [1]. The size of the dynamical gap is predicted to scale linearly with the inverse driving frequency [1]. On the other hand, charge carriers inside the Dirac cone need to be able to follow the driving field coherently over many cycles, which requires driving frequencies that are large compared to the inverse scattering time of the carriers [2]. Broers et al. [3] recently predicted a sweet spot for the driving frequency around 30 THz. We implemented a setup for time- and angle-resolved photoemission spectroscopy that combines a strong-field variable-wavelength multi-THz pump source with extreme ultraviolet probe pulses for putting these predictions to the test. In this talk we present our progress and discuss remaining challenges towards the experimental observation of Floquet effects in epitaxial graphene.
[1] T. Oka and H. Aoki, Phys. Rev. B 79, 081406(R) (2009) [2] Dunlap et al., Phys. Rev. B 34, 3625 (1986) [3] L. Broers and L. Mathey, Phys. Rev. Research. 4, 013057 (2022)
Keywords: Floquet topological insulator; Epitaxial graphene; tr-ARPES; multi-THz; Dynamical bandstructure engineering