Light-induced anomalous Hall effect in graphene

• Published in: Nature physics Vol. 16; no. 1; pp. 38 - 41
• Main Authors: McIver, J. W., Schulte, B., Stein, F.-U., Matsuyama, T., Jotzu, G., Meier, G., Cavalleri, A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2020; Nature Publishing Group
• Subjects: 639/766/119/2792/4128; 639/766/400/482; 639/766/400/584; Atomic; Circular polarization; Classical and Continuum Physics; Complex Systems; Computer architecture; Condensed Matter Physics; Conductance; Electromagnetism; Femtosecond pulses; Fermi level; Graphene; Hall effect; Letter; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Polarized light; Resistance; Theoretical; Topology
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/s41567-019-0698-y

Many non-equilibrium phenomena have been discovered or predicted in optically driven quantum solids 1 . Examples include light-induced superconductivity 2 , 3 and Floquet-engineered topological phases 4 – 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 switches 9 . 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 structure 4 , 5 , similar to the band structure originally proposed by Haldane 10 . 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 2 / h . A transient topological response in graphene is driven by a short pulse of light. When the Fermi energy is in the predicted band gap the Hall conductance is around two conductance quanta. An ultrafast detection technique enables the measurement.