When solids are exposed to intense optical fields, the intraband electron motion may influence interband transitions, potentially causing a transition of light-matter interaction from a quantum (photon-driven) regime to a semi-classical (field-driven) regime. We demonstrate this transition in monolayer graphene. We observe a carrier-envelope-phasedependent current in graphene irradiated with phase-stable two-cycle laser pulses, showing a striking reversal of the current direction as a function of the driving field amplitude at ~2 V/nm. This reversal indicates the transition into the field-driven (or strong-field) regime. We show furthermore that in this regime electron dynamics are governed by suboptical-cycle Landau-Zener-Stückelberg interference, comprised of coherent repeated Landau-Zener transitions. We expect these results to have direct ramifications for light-wave driven electronics in graphene.
Takuya Higuchi, Christian Heide, Konrad Ullmann, Heiko B. Weber, and Peter Hommelhoff, "Landau-Zener-Stückelberg interferometer on attosecond timescales in graphene," Proc. SPIE 10530, Ultrafast Phenomena and Nanophotonics XXII, 105300Z (Presented at SPIE OPTO: January 31, 2018; Published: 22 February 2018); https://doi.org/10.1117/12.2289540.
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