Space Charge Free Ultrafast Photoelectron Spectroscopy on Solids by a Narrowband Tunable Extreme Ultraviolet Light Source

TL;DR

This paper introduces a novel tunable narrowband high harmonic generation light source enabling space charge free ultrafast photoelectron spectroscopy on solids with high energy resolution and validated for time-resolved experiments.

Contribution

A new HHG light source with tunable narrow bandwidth and high repetition rate that achieves near Fourier transform limit conditions for ultrafast PES on solids.

Findings

Achieved ~22 meV energy resolution on gold at 40 K.

Validated space charge free photoelectric process close to Fourier limit.

Demonstrated effective TR-PES on Bi2Se3 with ultrafast pulses.

Abstract

Here we report on a novel High Harmonic Generation (HHG) light source designed for space charge free ultrafast photoelectron spectroscopy (PES) on solids. The ultimate overall energy resolution achieved on a polycrystalline Au sample is ~22 meV at 40 K. These results have been obtained at a photon energy of 16.9 eV with a pulse bandwidth of ~19 meV, by varying, up to 200 kHz, the photon pulses repetition rate and the photon fluence on the sample. These features set a new benchmark for tunable narrowband HHG sources. By comparing the PES energy resolution and the photon pulse bandwidth with a pulse duration of ~105 fs, as retrieved from time-resolved (TR) angle resolved (AR) PES experiments on Bi$_2$Se$_3$, we validate a way for a space charge free photoelectric process close to Fourier transform limit conditions for ultrafast TR-PES experiments on solids.