Past Event

Femtosecond science on-chip: Capturing light-induced anomalous Hall currents in graphene

March 11, 2019
10:00 AM - 11:00 AM
705 Pupin Hall

Many striking non-equilibrium phenomena have been discovered or predicted in quantum solids driven by femtosecond pulses of light, ranging from photo-induced superconductivity [1] to Floquet-engineered topological phases [2]. These effects are expected to lead to dramatic changes in electrical transport, but can only be comprehensively characterized or functionalized with a direct interface to electrical devices that operate at ultrafast speeds. This can be accomplished by adopting an ultrafast optoelectronic device architecture based on laser-triggered photoconductive switches. In this talk, I will present results demonstrating that a mid-infrared femtosecond pulse of circularly polarized light induces an anomalous Hall effect in monolayer graphene. The dependence of the effect on a gate potential used to tune the Fermi level reveals multiple features that directly reflect the emergence of a photon-dressed topological band structure in graphene, similar to the one originally proposed by Haldane [3], including a ∼60 meV wide plateau centered at the Dirac point. When the Fermi level lies within this plateau, the anomalous Hall conductance approaches 2e2/h. 

[1] D. Fausti et al.  Science 331, 189-191 (2011) 

[2] T. Oka & H. Aoki Phys. Rev. B 79, 081406 (2009)

[3] F.D.M. Haldane, Phys. Rev. Lett. 61, 2015-2018 (1988)

About the speaker

James McIver is a condensed matter physicist at the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg. He received his PhD in physics from Harvard University and is the recipient of an NSF graduate research fellowship and a Humboldt postdoctoral fellowship. His work focuses on understanding and controlling the dynamical transport properties of optically-driven functional materials using on-chip femtosecond electronics.

Photo of James McIver