James McIver: Femtosecond science on a chip: Capturing ultrafast anomalous Hall currents in optically-driven graphene

We are developing on-chip experiments to study the electronic transport properties of optically driven quantum materials on ultrafast timescales. The development of such experiments is important as it provides a new way to study non-equilibrium quantum phases, while simultaneously functionalizing their emergent electronic properties in the form of a real device. Moreover, embedding these materials in circuitry offers an unprecedented level of additional control that when combined with optical driving could stabilize or unveil emergent quantum effects previously inaccessible.

Using our ultrafast circuitry concept we have studied the non-equilibrium transport properties of optically driven graphene. We find that when graphene is held under a DC voltage bias and is illuminated by an ultrafast circularly polarized laser pulse, a transient photocurrent is generated transverse to the applied bias. By utilizing photoconductive switches embedded in our circuitry, we study the amplitude and temporal profile of these photocurrents. Our results indicate that we are measuring a light-induced anomalous Hall effect [1] and are consistent with the emergence of a dynamical quantum Hall insulator phase described by the Haldane model [2].

[1] T. Oka & H. Aoki, PRL 79, 081406 (2009)

[2] Haldane, PRL 61, 2015-2018 (1988)