Quantum interference visibility spectroscopy in two-color photoemission from tungsten needle tips

TL;DR

This study demonstrates two-color visibility spectroscopy in multi-photon photoemission from tungsten tips, revealing high and controllable interference visibility across a broad wavelength range, supported by a simple theoretical model.

Contribution

It introduces a novel two-color visibility spectroscopy method for solid-state nanoemitters, with comprehensive experimental and theoretical analysis of quantum pathway interference.

Findings

Photoemission shows 90% +/- 5% visibility across a broad wavelength range.

Visibility can be tuned from 0 to nearly 100% by adjusting intensity ratios.

Theoretical model accurately explains the experimental observations.

Abstract

When two-color femtosecond laser pulses interact with matter, electrons can be emitted through various multiphoton excitation pathways. Quantum interference between these pathways gives rise to a strong oscillation of the photoemitted electron current, experimentally characterized by its visibility. In this work, we demonstrate two-color visibility spectroscopy of multi-photon photoemission from a solid-state nanoemitter. We investigate the quantum pathway interference visibility over an almost octave-spanning wavelength range of the fundamental femtosecond laser pulses and their second-harmonic. The photoemission shows a high visibility of 90% +/- 5%, with a remarkably constant distribution. Furthermore, by varying the relative intensity ratio of the two colors, we find that we can vary the visibility between 0 and close to 100%. A simple but highly insightful theoretical model allows us to explain all observations, with excellent quantitative agreements. We expect this work to be universal to all kinds of photo-driven quantum interference, including quantum control in physics, chemistry and quantum engineering.