Evidence of coherence in strong-field electron photoemission from a semiconductor

TL;DR

This paper provides experimental evidence of coherent ultrashort hot electron emission from nanostructured semiconductors under strong laser fields, revealing harmonic signatures and attosecond timing, advancing quantum device development.

Contribution

It demonstrates direct observation of coherence in strong-field electron emission from semiconductors, a previously unobserved phenomenon, using sub-wavelength field enhancement techniques.

Findings

Observation of both odd and even harmonic orders in electron spectra.

Evidence of attosecond timing in electron emission.

Similarity to metallic nanotip electron emission phenomena.

Abstract

Strong-field quantum electronics is emerging as a potential candidate in information processing but still coherence vs decoherence is a primary concern of the concept. Strong-field coherent processes in band gap materials have led during the last decade to the emergence of high harmonic generation in semiconductors, petahertz electronics, or strong-field quantum states. However, the coherent behavior of the sub-optical cycle-driven electrons has never been directly observed. We report here on the experimental evidence of coherent ultrashort emission of hot electrons from a nanostructured semiconductor. Our method uses sub-wavelength electric field enhancement to localize the electron emission within a nanometer-scale spot. We found similarities with the electron emission from metallic nanotips in the strong-field regime, a topic that has opened a vast domain of applications during the last decade. The electron spectra display both odd and even harmonic orders of the driving femtosecond laser frequency, a signature of the coherent nature of the electron emission and their attosecond timing. Our findings complete our knowledge of phenomena governing coherent strong-field processes in semiconductors and open perspectives for the generation of future quantum devices operating in the strong-field regime.