We employ attosecond core-level x-ray absorption spectroscopy to unravel the intricate many-body interactions occurring in strongly photo-excited semi-metallic graphite. This allows us to unveil remarkably high conductivity and delineate deviations from the single particle bandstructure.
Fundamental electron dynamics at the attosecond frontier and their direct coupling to structural dynamics of matter yield novel insights into the energy-distribution and protection mechanisms of Nature. The angular-streaking technique has exclusively demonstrated its capability of obtaining the full time-energy structure of XFEL pulses with attosecond resolution directly in the time-domain, thus enabling XFELs to study electron dynamics from element-specific vistas and their importance as onset of subsequent structural dynamics. We will present latest advances of this technique together with first results from the 2022 EuXFEL atto-campaign and the complementary prospects of the FLASH 2020+ innovation project at DESY.
X-ray absorption fine-structure (XAFS) spectroscopy is a well-established technique capable of extracting information about a material’s electronic and lattice structure with atomic resolution. While the near-edge region (XANES) of a XAFS spectrum provides information about the electronic configuration, structural information is extracted from the extended XAFS (EXAFS) spectrum, consisting of several hundreds of eV above the absorption edge. With the advent of high harmonic sources, reaching photon energies in soft x-ray (SXR) region, it now becomes possible to connect the spectroscopic capabilities of XAFS to the unprecedented attosecond temporal resolution of a high harmonic source allowing the observation of electronic and lattice dynamics in real time [1,2].
Layered materials, such the transition-metal dichalcogenide TiS2 or graphite, are an emerging class of materials with attractive structural and electronic properties as they can be thinned to a single atomic layer with electron mobilities resembling that of a metal, semiconductor, or semi-metal.
In this work, we utilized broadband water-window-covering attosecond SXR pulses (300 as, ranging from 200
- 550 eV) capable of accessing orbital-specific K- and L-edges of such layered materials to perform transient XAFS
with attosecond time resolution [3,4].
[1] Teichmann, S. et al, "0.5-keV soft x-ray attosecond continua", Nat. Commun. 7, 11493 (2016).
[2] Cousin S. et al, "Attosecond streaking in the water window: a new regime of attosecond pulse characterization", Phys. Rev. X, 7, 041030 (2017).
[3] Buades, B. et al., “Dispersive soft x-ray absorption fine-structure spectroscopy in graphite with an attosecond pulse”, Optica 5 (5), 502 (2018).
[4] Buades, B. et al., “Attosecond-resolved petahertz carrier motion in semi-metallic TiS2”, arXiv: 1808.06493 (2018).
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