Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 66: Ultrafast electron dynamics at surface and interfaces III

O 66.4: Talk

Wednesday, March 11, 2026, 16:00–16:15, TRE/MATH

Ultrafast Band-Gap Renormalization in Bilayer Graphene — •Eduard Moos¹, ZhiYuan Deng¹, Hauke Beyer¹, Arpit Jain⁴, Chengye Dong⁴, Joshua A. Robinson⁴, Kai Rossnagel^1,2,3, and Michael Bauer^1,2 — ¹Kiel University, Germany — ²Kiel Nano, Surface and Interface Science KiNSIS, Germany — ³Electron Synchrotron DESY, Germany — ⁴Pennsylvania State University, United States

We demonstrate, by femtosecond time- and angle-resolved photoemission spectroscopy, that photoinduced interlayer charge transfer in a heterostructure consisting of Bernal-stacked bilayer graphen and a single atomic layer of silver on 6H-SiC(0001) transiently modulates the intrinsic potential landscape across the silver-graphene interface. Acting as an ultrafast electronic gate, this drives momentum-dependent band renormalizations, resulting in a transient band-gap opening on femtosecond timescales. Simultaneously, the photogenerated hot-carrier population enhances electronic screening, leading to a subsequent closing of the band-gap beyond the thermal equilibrium value. These findings reveal two different mechanisms for a photoinduced, reversible control of the electronic band structure in bilayer graphen — interlayer charge transfer and hot-carrier enhanced screening — providing a general framework for the ultrafast control of electronic properties in graphene-based heterostructures. They further open novel pathways for the realization of ultrafast optoelectronic devices and the exploration of correlated quantum phases in bilayer graphene under nonequilibrium conditions.

Keywords: ultrafast; trARPES; band renormalization; bilayer-graphene; interlayer charge transfer