Giant enhancement of attosecond tunnel ionization competes with disorder-driven decoherence in silicon

TL;DR

This study reveals a giant enhancement in attosecond tunnel ionization in amorphous silicon, demonstrating how disorder influences high-harmonic generation and providing new insights into ultrafast decoherence and nanoscale control.

Contribution

It uncovers a >250-fold increase in tunnel ionization yield in amorphous silicon and links disorder-driven decoherence to changes in high-harmonic spectra, advancing understanding of ultrafast solid-state dynamics.

Findings

Giant enhancement (>250x) of tunnel ionization in amorphous silicon.

Disorder-induced decoherence dampens electron-hole polarization.

HHG spectroscopy detects residual order beyond conventional methods.

Abstract

High-harmonic generation (HHG) is a strong-field phenomenon that is sensitive to the attosecond dynamics of tunnel ionization and coherent transport of electron-hole pairs in solids. While the foundations of solid HHG have been established, a deep understanding into the nature of decoherence on sub-cycle timescales remains elusive. Furthermore, there is a growing need for tools to control ionization at the nanoscale. Here, we study HHG in silicon along a crystalline-to-amorphous (c-Si to a-Si) structural phase transition and observe a dramatic reshaping of the spectrum, with enhanced lower-order harmonic yield accompanied by quenching of the higher-order harmonics. Modelling the real-space quantum dynamics links our observations to a giant enhancement (>250 times) of tunnel ionization yield in the amorphous phase and a disorder-induced decoherence that damps the electron-hole polarization over approximately six lattice sites. HHG spectroscopy also reveals remnant order that was not apparent with conventional probes. Finally, we observe a rapid and targeted non-resonant laser annealing of amorphous silicon islands. Our results offer a unique insight into attosecond decoherence in strong-field phenomena, establish HHG spectroscopy as a probe of structural disorder, and pave the way for new opportunities in lightwave nanoelectronics.