Light-induced anomalous Hall effect in graphene
James McIver, Benedikt Schulte, Stein, F., T. Matsuyama, Gregor Jotzu, Guido Meier, A. Cavalleri
Abstract
Many non-equilibrium phenomena have been discovered or predicted in optically driven quantum solids<sup>1</sup>. Examples include light-induced superconductivity<sup>2,3</sup> and Floquet-engineered topological phases<sup>4,5,6,7,8</sup>. 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 switches<sup>9</sup>. 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 Haldane<sup>10</sup>. 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 e<sup>2</sup>/h.