Ultrafast filling of an electronic pseudogap in an incommensurate crystal

TL;DR

This study reveals that in an incommensurate crystal, a photoexcited pseudogap can be filled within 80 femtoseconds due to strong electron-phonon coupling, providing insights into electronic localization in aperiodic structures.

Contribution

It demonstrates ultrafast pseudogap filling in an incommensurate crystal, highlighting the role of strong electron-phonon interactions in electronic localization.

Findings

Partial filling of pseudogap within 80 fs after photoexcitation

Electronic energy transfer to lattice modes occurs on a similar timescale

Strong electron-phonon coupling linked to incommensurate distortion

Abstract

We investigate the quasiperiodic crystal (LaS)1.196(VS2) by angle and time resolved photoemission spectroscopy. The dispersion of electronic states is in qualitative agreement with band structure calculated for the VS2 slab without the incommensurate distortion. Nonetheless, the spectra display a temperature dependent pseudogap instead of quasiparticles crossing. The sudden photoexcitation at 50 K induces a partial filling of the electronic pseudogap within less than 80 fs. The electronic energy flows into the lattice modes on a comparable timescale. We attribute this surprisingly short timescale to a very strong electron-phonon coupling to the incommensurate distortion. This result sheds light on the electronic localization arising in aperiodic structures and quasicrystals.