Direct view of exciton and carrier dynamics in twisted bilayer graphene

Gianmarco Gatti; Anders S. Mortensen; Zhihao Jiang; Alfred J. H. Jones; Gesa-R. Siemann; Thomas S. Nielsen; Søren Ulstrup; Naina Kushwaha; Bruce Weaver; Yu Zhang; Emma Springate; Charlotte E. Sanders; Vibha Reddy; Ulrich Starke; Philip Hofmann

arXiv · 2610.17984

Direct view of exciton and carrier dynamics in twisted bilayer graphene

Gianmarco Gatti·Anders S. Mortensen·Zhihao Jiang·Alfred J. H. Jones·Gesa-R. Siemann·Thomas S. Nielsen·Søren Ulstrup·Naina Kushwaha·Bruce Weaver·Yu Zhang·Emma Springate·Charlotte E. Sanders·Vibha Reddy·Ulrich Starke·Philip Hofmann

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Abstract

Twisted bilayer graphene (tBLG) on H-intercalated SiC (twist angle of $9 \pm 1^{\circ}$) is studied by position\mbox{-}, time\mbox{-}, and angle-resolved photoemission spectroscopy (ARPES). Both graphene layers are hole doped, with a Dirac-point offset of 30~meV. Time-resolved ARPES near the van Hove singularity reveals a spectral feature within the hybridization-induced band gap, together with excited electrons in the conduction band. The in-gap feature exhibits distinct dynamics, and its binding energy and $k$-space location are consistent with the proposed non-hydrogenic ``ghost-Fano'' exciton arising from destructive interference between two nearly degenerate excitonic channels. Near the Dirac points, the twist separates the largely layer-polarized Dirac cones in momentum space, providing direct layer selectivity. We find markedly different peak electronic temperatures in the two graphene layers, even though their subsequent cooling dynamics are very similar. We attribute this to an ultrafast interlayer redistribution of electronic energy, driven by an interlayer electric field that arises from the different doping in the layers.

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Gianmarco Gatti, Anders S. Mortensen, Zhihao Jiang, Alfred J. H. Jones, Gesa-R. Siemann, Thomas S. Nielsen, Søren Ulstrup, Naina Kushwaha, Bruce Weaver, Yu Zhang, Emma Springate, Charlotte E. Sanders, Vibha Reddy, Ulrich Starke, Philip Hofmann. 2026-10-13. Direct view of exciton and carrier dynamics in twisted bilayer graphene. https://arxiv.org/abs/2610.17984

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