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.
@article{arxiv.1306.5817,
title = {Orbital-Selective Mottness in KxFe2-ySe2 Superconductors Revealed by Pump-Probe Spectroscopy},
author = {Wei Li and Chunfeng Zhang and Shenghua Liu and Xiaxin Ding and Xuewei Wu and Xiaoyong Wang and Hai-Hu Wen and Min Xiao},
journal= {arXiv preprint arXiv:1306.5817},
year = {2014}
}