Ultrafast Quasiparticle Dynamics and Electron-Phonon Coupling in (Li0.84Fe0.16)OHFe0.98Se

TL;DR

This study uses ultrafast spectroscopy to measure electron-phonon coupling in an intercalated FeSe superconductor, revealing a potential universal role of EPC in iron-based superconductivity.

Contribution

It provides the first measurement of electron-phonon coupling in (Li0.84Fe0.16)OHFe0.98Se and links EPC strength to superconducting transition temperatures across FeSe-based superconductors.

Findings

Electron-phonon coupling constant {1}A1g is 0.221.04.

Positive correlation between EPC and Tc in FeSe-based superconductors.

Universal role of EPC suggested in iron-based superconductor mechanisms.

Abstract

Distinctive superconducting behaviors between bulk and monolayer FeSe make it challenging to obtain a unified picture of all FeSe-based superconductors. We investigate the ultrafast quasiparticle (QP) dynamics of an intercalated superconductor (Li1-xFex)OHFe1-ySe, which is a bulk crystal but shares a similar electronic structure with single-layer FeSe on SrTiO3. We obtain the electron-phonon coupling (EPC) constant {\lambda}A1g (0.22 +/- 0.04), which well bridges that of bulk FeSe crystal and single-layer FeSe on SrTiO3. Moreover, we find that such a positive correlation between {\lambda}A1g and superconducting Tc holds among all known FeSe-based superconductors, even in line with reported FeAs-based superconductors. Our observation indicates possible universal role of EPC in the superconductivity of all known categories of iron-based superconductors, which is a critical step towards achieving a unified superconducting mechanism for all iron-based superconductors.