Regensburg 2025 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 35: 2D Materials: Electronic Structure and Exitations II (joint session O/HL/TT)

HL 35.6: Talk

Wednesday, March 19, 2025, 12:00–12:15, H11

Ultrafast Charge Separation on the Nanoscale Induced by a Uniform Field — •Jan-Philip Joost and Michael Bonitz — Kiel University, Institute for Theoretical Physics and Astrophysics, 24098 Kiel, Germany

When illuminated by white light, atoms, molecules, and materials absorb only certain characteristic energy contributions based on their absorption properties. Here, we show that this effect can be translated from energy to space: a spatially uniform laser pulse can create strongly localized carrier excitations and spatial charge separation on the sub-nanometer scale within a few femtoseconds, possibly opening new avenues for nanoelectronics. A promising candidate are small graphene heterostructures, which exhibit a pronounced space dependence of the DOS with strongly localized topologically protected states [1]. Direct evidence for this effect is presented by performing extensive NEGF simulations for these systems that take into account strong coupling and dynamical screening [2]. Further, we demonstrate multiple ways to excite targeted areas of the nanostructures, such as a proper choice of the laser energy, polarization, or carrier-envelope phase. Moreover, we find that the observed effects greatly benefit from surface screening, while in free-standing systems the targeted charge excitation is restricted by strongly bound excitons. The findings are expected to be applicable for a broad class of nanoscale monolayer clusters of graphene or TMDCs.

[1] J.-P. Joost et al., Nano Lett. 19, 9045 (2019)

[2] J.-P. Joost et al., Phys. Rev. B 105, 165155 (2022)

Keywords: NEGF; nonequilibrium; dynamics; excitons; excitation