Photo-induced Superconducting State with Long-lived Disproportionate Band Filling in FeSe

TL;DR

This study demonstrates the induction of a high-temperature superconducting state in FeSe through photo-excitation, revealing a long-lived, non-equilibrium electronic state with potential for ultrafast superconductor control.

Contribution

It provides direct observation of a photo-induced superconducting state in FeSe with long-lived electronic changes, expanding the understanding of light-driven superconductivity in multiband materials.

Findings

Photo-induced superconductivity observed in FeSe.

Transient electronic state persists from 50 fs to 800 ps.

Supports the emergence of a high-Tc superconducting phase after photo-excitation.

Abstract

Photo-excitation is a very powerful way to instantaneously drive a material into a novel quantum state without any fabrication, and variable ultrafast techniques have been developed to observe how electron-, lattice-, and spin-degrees of freedom change. One of the most spectacular phenomena is photo-induced superconductivity, and it has been suggested in cuprates that the transition temperature Tc can be enhanced from original Tc with significant lattice modulations. Here we show another photo-induced high-Tc superconducting state in the iron-based superconductor FeSe with semi-metallic hole and electron bands. The transient electronic state in the entire Brillouin zone is directly observed by the time- and angle-resolved photoemission spectroscopy using extreme ultraviolet pulses obtained from high harmonic generation. Our results of dynamical behaviors on timescales from 50 fs to 800 ps consistently support the favorable superconducting state after photo-excitation well above Tc. This finding demonstrates that multiband iron-based superconductors emerge as an alternative candidate for photo-induced superconductors.