Orbital-Selective Mottness in KxFe2-ySe2 Superconductors Revealed by Pump-Probe Spectroscopy

TL;DR

This study uses pump-probe spectroscopy to reveal orbital-selective Mottness in KxFe2-ySe2 superconductors, showing how electron correlations influence phase transitions and superconductivity.

Contribution

It provides experimental evidence of orbital-selective Mott phase transition in iron-based superconductors using transient optical spectroscopy.

Findings

Observation of coherent acoustic phonons in the superconducting phase

Temperature-dependent suppression of oscillatory components

Enhanced slow decay component at higher temperatures

Abstract

We report transient optical signatures of the orbital-selective Mottness in superconducting KxFe2-ySe2 crystals by using dual-color pump-probe spectroscopy. Besides multi-exponential decay recovery dynamics of photo-induced quasiparticles, a damped oscillatory component due to coherent acoustic phonons emerges when the superconducting phase is suppressed by increasing the temperature or excitation power. The oscillatory component diminishes with significant enhancement of a slow decay component upon raising temperature to 150-160 K. These results are in consistence with the picture of orbital-selective Mott phase transition, indicating a vital role played by electron correlation in the iron-based superconductors.