Electronic coherences are observed in silicon by attosecond transient absorption spectroscopy. Various sub-4 fs oscillations across the conduction band reveal complex couplings between valence-conduction and conduction-conduction bands indicating pathways for coherent preparation of highly excited electrons.

A harmonic continuum extending up to 375 eV is generated from 750 μJ, 9 fs mid-IR pulses centered at 1300 nm. The development of this source and its use for attosecond transient absorption spectroscopy experiments at the carbon K-edge are discussed.

Attosecond transient absorption spectroscopy at the M4,5-edge of Ge following ultrafast photoexcitation reveals valley-resolved hot electron and hole relaxation, carrier recombination and trapping in Ge and Si-Ge alloy in unprecedented clarity and simultaneously.

Electron-hole dynamics is measured by attosecond transient absorption in silicongermanium alloy. The germanium atoms act as reporter atoms by time-dependent probing the M4,5-edge, revealing electron and hole dynamics, as well as a new midgap feature.