Abstract
Recent developments in attosecond technology led to table-top x-ray spectroscopy in the soft x-ray range, thus uniting the element- and state-specificity of core-level x-ray absorption spectroscopy with the time resolution to follow electronic dynamics in real-time. We describe recent work in attosecond technology and investigations into materials such as Si, SiO2, GaN, Al2O3, Ti, and TiO2, enabled by the convergence of these two capabilities. We showcase the state-of-the-art on isolated attosecond soft x-ray pulses for x-ray absorption near-edge spectroscopy to observe the 3d-state dynamics of the semi-metal TiS2 with attosecond resolution at the Ti L-edge (460 eV). We describe how the element- and state-specificity at the transition metal L-edge of the quantum material allows us to unambiguously identify how and where the optical field influences charge carriers. This precision elucidates that the Ti:3d conduction band states are efficiently photo-doped to a density of 1.9 × 1021 cm−3. The light-field induces coherent motion of intra-band carriers across 38% of the first Brillouin zone. Lastly, we describe the prospects with such unambiguous real-time observation of carrier dynamics in specific bonding or anti-bonding states and speculate that such capability will bring unprecedented opportunities toward an engineered approach for designer materials with pre-defined properties and efficiency. Examples are composites of semiconductors and insulators like Si, Ge, SiO2, GaN, BN, and quantum materials like graphene, transition metal dichalcogens, or high-Tc superconductors like NbN or LaBaCuO. Exiting are prospects to scrutinize canonical questions in multi-body physics, such as whether the electrons or lattice trigger phase transitions.
Highlights
Until the last decade, ultrafast soft x-ray spectroscopies were nearly exclusively available at synchrotrons, where tens- to hundreds-of-picoseconds temporal resolution was “state-of-the-art.” Femto-slicing was developed to improve the time resolution to the $150 femtoseconds range,1,2 but at the expense of photon flux
We have described the recent developments of attosecond technology and x-ray spectroscopy
Beyond the field’s background, we showcase the state of the art with an attosecond x-ray absorption nearedge spectroscopy (XANES) measurement at the Ti L2,3 edge at 460 eV of a transition metal dichalcogen (TMDC) quantum material
Summary
Ultrafast soft x-ray spectroscopies were nearly exclusively available at synchrotrons, where tens- to hundreds-of-picoseconds temporal resolution was “state-of-the-art.” Femto-slicing was developed to improve the time resolution to the $150 femtoseconds range, but at the expense of photon flux. Isolated attosecond soft x-ray pulses with water-window coverage are available, and the utility of attosecond technology for x-ray absorption nearedge spectroscopy (XANES) and extended x-ray absorption fine structure (EXAFS) was demonstrated In parallel with these developments, the first self-amplified spontaneous emission (SASE) operation of an accelerator has been shown to yield x-ray radiation.. This section intends to showcase what is currently possible with attosecond XANES in the water-window SXR regime to stimulate interdisciplinary collaborations between the solid-state, materials, ultrafast x-ray, and attoscience communities The realization of such collaborations will guide the development of attosecond table-top x-ray sources, further x-ray spectroscopy theoretical methods to better model complicated material systems, and advance our understanding of complex multi-component quantum materials of relevance to address today’s problems
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