Ultrafast electronic line width broadening in the C 1s core level of graphene

Abstract

Core level binding energies and absorption edges are at the heart of many experimental techniques concerned with element-specific structure, electronic structure, chemical reactivity, elementary excitations and magnetism. X-ray photoemission spectroscopy (XPS) in particular, can provide information about the electronic and vibrational many-body interactions in a solid as these are reflected in the detailed energy distribution of the photoelectrons. Ultrafast pump-probe techniques add a new dimension to such studies, introducing the ability to probe a transient state of the many-body system. Here we use a free electron laser to investigate the effect of a transiently excited electron gas on the core level spectrum of graphene, showing that it leads to a large broadening of the C 1s peak. Confirming a decade-old prediction, the broadening is found to be caused by an exchange of energy and momentum between the photoemitted core electron and the hot electron system, rather than by vibrational excitations. This interpretation is supported by a line shape analysis that accounts for the presence of the excited electrons. Fitting the spectra to this model directly yields the electronic temperature of the system, in agreement with electronic temperature values obtained from valence band data. Furthermore, making use of time- and momentum-resolved C 1s spectra, we illustrate how the momentum change of the outgoing core electrons leads to a small but detectable change in the time-resolved photoelectron diffraction pattern and to a nearly complete elimination of the core level binding energy variation associated with the narrow $\sigma$-band in the C 1s state. The results demonstrate that the XPS line shape can be used as an element-specific and local probe of the excited electron system and that X-ray photoelectron diffraction investigations remain feasible at very high electronic temperatures.

arXiv comment16 pages, 12 figures

References in corpus (24)

• Electronic transport in two dimensional graphene
• Quasi-free Standing Epitaxial Graphene on SiC by Hydrogen Intercalation
• Snapshots of non-equilibrium Dirac carrier distributions in graphene
• Direct view on the ultrafast carrier dynamics in graphene
• The quasi-free-standing nature of graphene on H-saturated SiC(0001)
• Ultrafast Relaxation Dynamics of Hot Optical Phonons in Graphene
• Electron-phonon coupling and electron self-energy in electron-doped graphene: calculation of angular resolved photoemission spectra
• Energy Relaxation of Hot Dirac Fermions in Graphene
• Characterization of graphene through anisotropy of constant-energy maps in angle-resolved photoemission
• Examining electron-boson coupling using time-resolved spectroscopy
• Tunable Carrier Multiplication and Cooling in Graphene
• Time- and momentum-resolved photoemission studies using time-of-flight momentum microscopy at a free-electron laser
• Large area quasi-free standing monolayer graphene on 3C-SiC(111)
• Decoding the ultrafast formation of a Fermi-Dirac distributed electron gas
• Observation of an excitonic Mott transition through ultrafast core-$\text{cum}$-conduction photoemission spectroscopy
• Band dispersion in the deep 1s core level of graphene
• Electromagnetic dressing of the electron energy spectrum of Au(111) at high momenta
• Photoemission Signatures of Non-Equilibrium Carrier Dynamics from First Principles
• High-temperature behaviour of supported graphene: electron-phonon coupling and substrate-induced doping
• Ultrafast Momentum Imaging of Pseudospin-Flip Excitations in Graphene
• Extracting the Temperature of Hot Carriers in Time- and Angle-Resolved Photoemission
• An open-source, end-to-end workflow for multidimensional photoemission spectroscopy
• Core-level spectra from graphene
• Stroboscopic Tests for Thermalization of Electrons in Pump/Probe Experiments

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• Spin- and time-resolved photoelectron spectroscopy and diffraction studies using time-of-flight momentum microscopes
• Multispectral time-resolved energy-momentum microscopy using high-harmonic extreme ultraviolet radiation
• Probing excitons with time-resolved momentum microscopy
• Tracking the surface atomic motion in a coherent phonon oscillation