Many non-equilibrium phenomena have been discovered or predicted in optically driven quantum solids1. Examples include light-induced superconductivity2,3 and Floquet-engineered topological phases4,5,6,7,8. These are short-lived effects that should lead to measurable changes in electrical transport, which can be characterized using an ultrafast device architecture based on photoconductive switches9. Here, we report the observation of a light-induced anomalous Hall effect in monolayer graphene driven by a femtosecond pulse of circularly polarized light. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that reflect a Floquet-engineered topological band structure4,5, similar to the band structure originally proposed by Haldane10. This includes an approximately 60 meV wide conductance plateau centred at the Dirac point, where a gap of equal magnitude is predicted to open. We find that when the Fermi level lies within this plateau the estimated anomalous Hall conductance saturates around 1.8 ± 0.4 e2/h.
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The data represented in Figs. 2–4 are available with the online version of this paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author on reasonable request.
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We acknowledge H. Aoki, L. Mathey, M. Nuske, A. Rubio, S.A. Sato, M.A. Sentef and P. Tang for fruitful discussions and B. Fiedler, B. Höhling, E. König and M. Volkmann for technical support. The research leading to these results received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2013)/ERC Grant Agreement no. 319286 (QMAC). J.W.M. received funding from the Alexander von Humboldt Foundation.
The authors declare no competing interests.
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McIver, J.W., Schulte, B., Stein, F. et al. Light-induced anomalous Hall effect in graphene. Nat. Phys. (2019) doi:10.1038/s41567-019-0698-y
Physical Review B (2019)
Physical Review B (2019)