We present an application of Eliashberg theory of superconductivity to study a set of novel superconducting systems with a wide range of structural and chemical properties. The set includes three intercalated group-IV honeycomb layered structures, SH 3 at 200 GPa (the superconductor with the highest measured critical temperature), the similar system SeH 3 at 150 GPa, and a lithium doped mono-layer of black phosphorus. The theoretical approach we adopt is a recently developed, fully ab initio Eliashberg approach that takes into account the Coulomb interaction in a full energy-resolved fashion avoiding any free parameters like μ +. This method provides reasonable estimations of superconducting properties, including T C and the excitation spectra of superconductors.

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Attosecond duration relativistic electron bunches travelling through an undulator can generate brilliant coherent radiation in the visible to vacuum ultraviolet spectral range. We present comprehensive numerical simulations to study the properties of coherent emission for a wide range of electron energies and bunch durations, including space-charge effects. These demonstrate that electron bunches with r.m.s. duration of 50 as, nominal charge of 0.1 pC and energy range of 100–250 MeV produce $$10^9$$ 10 9 coherent photons per pulse in the 100–600 nm wavelength range. We show that this can be enhanced substantially by self-compressing negatively chirped 100 pC bunches in the undulator to produce $$10^{14}$$ 10 14 coherent photons with pulse duration of 0.5–3 fs.

Attosecond core-level soft X-ray spectroscopy is shown to image the energy conversion pathways between photons, charge carriers and lattice in real time in graphite.