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Interface-localized states mediate ultrafast cooling of hot electrons in epitaxial graphene

R. Stefanuik1,*, A. Kuklin1, T. Leitner2,3, J. A. Terschlüsen2, U. B. Cappel2,4, H. Siegbahn2, S. Plogmaker2, A. Sandell2, O. Karis2 et al.

J. Söderström1, N. Mårtensson2, S. Svensson1, H. Ågren1, M. Venkata Kamalakar2, R. Ovsyannikov3, H. Rensmo2,4, and R. Knut2

  • 1Chemical and Bio-Molecular Physics, Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
  • 2Condensed Matter Physics of Energy Materials, Division of X-ray Photon Science, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
  • 3Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Strasse 15, 12489 Berlin, Germany
  • 4Wallenberg Initiative Materials Science for Sustainability, Department of Physics and Astronomy, Uppsala University, 751 20 Uppsala, Sweden

  • *Contact author: robert.stefanuik@physics.uu.se
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Phys. Rev. B 114, 154304 – Published 9 September, 2026

DOI: https://doi.org/10.1103/l7qv-85gw

Abstract

In this study, we use time- and angle-resolved photoelectron spectroscopy to investigate electron relaxation dynamics in an epitaxially grown graphene monolayer on SiC. Our findings reveal significantly faster relaxation of photoexcited electrons in non-hydrogen-intercalated epitaxial graphene compared to that for previously reported hydrogen-intercalated graphene structures. The differences in relaxation time are modeled by a combination of density function theory in conjunction with ab initio nonadiabatic molecular dynamics, providing a comprehensive explanation of electron relaxation pathways. This study highlights the critical influence of substrate interactions on the relaxation mechanisms in graphene, offering different perspectives for tailoring graphene electronic properties through controlled intercalation techniques.

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Phys. Rev. B 114, 154304– Published 9 September, 2026
  • Received 25 September 2025
  • Revised 31 March 2026
  • Accepted 4 August 2026
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