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O: Fachverband Oberflächenphysik

O 72: Mini-Symposium: Coherent band structure engineering with light II

O 72.4: Invited Talk

Wednesday, March 3, 2021, 14:30–15:00, R2

Light-induced anomalous Hall effect in graphene — •James McIver — Max Planck Institute for the Structure and Dynamics of Matter, Hamburg, Germany

Optical driving has been proposed as a means of engineering topological properties in topologically trivial systems. One proposal for such a "Floquet topological insulator" is based on breaking time-reversal symmetry in graphene through a coherent interaction with circularly polarized light [1]. This was predicted to lift the degeneracy of the Dirac point, opening a topological band gap in the resulting photon-dressed band structure accompanied by the formation of dressed chiral edge states [2]. In this talk, I will report on our recent observation of a light-induced anomalous Hall effect in monolayer graphene driven by an intense femtosecond pulse of circularly polarized light [3]. We probed electrical transport using an ultrafast device architecture based on photoconductive switches. The dependence of the anomalous Hall effect on a gate potential used to tune the equilibrium Fermi level revealed multiple features that reflect a Floquet-engineered topological band structure. This included an approximately 60 meV wide conductance plateau centered at the Dirac point, where a gap of equal magnitude was predicted to open. We found that when the Fermi level was tuned within this plateau, the estimated anomalous Hall conductance saturated around 1.8 +/- 0.4 e^2/h. [1] T. Oka & H. Aoki. Phys. Rev. B 79, 081406 (2009) [2] T. Kitagawa et al. Phys. Rev. B 84, 235108 (2011) [3] J.W. McIver et al. Nature Physics 16, 38 (2020)