The superconducting critical temperature Tc of intercalated iron-selenide superconductor (Li,Fe)OHFeSe (FeSe11111) can be increased to 42 K from 8 K of bulk FeSe. It shows remarkably similar electronic properties as the high-Tc monolayer FeSe and provides a bulk counterpart to investigate the origin of enhanced superconductivity. Unraveling the nature of excitations is crucial for understanding the pairing mechanism in high-Tc iron selenides. Here we use resonant inelastic x-ray scattering (RIXS) to investigate the excitations in FeSe11111. Our high-quality data exhibit several Raman-like excitations, which are dispersionless and isotropic in momentum transfer and robust against varying Tc. Using atomic multiplet calculations, we assign the low-energy ∼0.3 and 0.7 eV Raman peaks as local eg−eg and eg−t2g orbital excitations. The intensity of these two features decreases with increasing temperature, suggesting a primary contribution of the orbital fluctuations. Our results highlight the importance of orbital degree of freedom for high-Tc iron selenides.
@article{arxiv.2110.05361,
title = {Dispersionless orbital excitations in (Li,Fe)OHFeSe superconductors},
author = {Qian Xiao and Wenliang Zhang and Teguh Citra Asmara and Dong Li and Qizhi Li and Shilong Zhang and Yi Tseng and Xiaoli Dong and Yao Wang and Cheng-Chien Chen and Thorsten Schmitt and Yingying Peng},
journal= {arXiv preprint arXiv:2110.05361},
year = {2022}
}