Dispersionless orbital excitations in (Li,Fe)OHFeSe superconductors

ORAL

Abstract

The origin of superconductivity in Fe-based superconductors remains unclear. Although spin fluctuation plays an important role in Fe-based superconductors, other factors, such as orbital fluctuation, are also in play [1,2]. The intercalated iron selenide (Li,Fe)OHFeSe (FeSe11111) is a single-phase bulk superconductor, which can reach a high Tc of 42K [3,4]. Intriguingly, it shows remarkably similar electronic behaviors as those in monolayer FeSe with the Tc up to 65K [5], providing a bulk counterpart to explore the origin of high Tc in iron selenides. Here we performed an extensive study on FeSe11111 by using resonant inelastic x-ray scattering (RIXS) at Fe L3-edge [6]. We have observed four Raman-like features at ∼ 0.1 eV, ∼ 0.3 eV, ∼ 0.7 eV, ∼ 2.5 eV, which are dispersionless versus momentum transfer. Moreover, these excitations show different temperature behaviors. Using atomic multiplet calculations we identify the excitations at ∼ 0.3 and 0.7 eV as local eg - eg and eg - t2g orbital excitations involving spin degrees of freedom. Our results uncover the excitations in FeSe11111 and provide an important insight to understand the superconductivity in iron selenides.

[1] Dai, P.  Rev. Mod. Phys. 87, 855-896 (2015).

[2] Kontani, H. & Onari, S. Phys. Rev. Lett.104,157001  (2010).

[3] Dong, X. et al. Phys. Rev. B 92, 064515 (2015).

[4] Lu,  X.  F.et al. Nature Ma-terials14, 325–329 (2015)

[5] Zhao, L. et al. Nature Communications 7, 10608 (2016).

[6] Xiao, Q. et al. arXiv:2110.05361 (2021).

*This work was performed at the ADRESS beamline of the Swiss Light Source using the SAXES instrument jointly built by Paul Scherrer Institut, Switzerland, Politecnico di Milano, Italy and EPFL, Switzerland. Y.Y.P. is grateful for nancial support from the Ministry of Science and Technology of China (Grant No. 2019YFA0308401) and the National Natural Science Foundation of China (Grant No. 11974029). T.S. acknowledges support by the Swiss National Science Foundation through Grant Numbers 200021_178867, CRSII2_160765/1 and CRSII2_141962. T.C.A. acknowledges funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skl odowska-Curie grant agreement No. 701647 (PSI-FELLOW-II-3i program). X.L.D. is grateful for financial support from the National Natural Science Foundation of China (Grant Nos. 12061131005, 11834016 and 11888101), the Strategic Priority Research Program of Chinese Academy of Sciences (XDB25000000). We appreciate the help with sample prepar

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Publication: Xiao, Q. et al., arXiv:2110.05361 (2021).

Presenters

  • Qian Xiao

    • Peking university

Authors

  • Qian Xiao

    • Peking university

  • Wenliang Zhang

    • Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland

  • Teguh C Asmara

    • Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland

  • Dong Li

    • Chinese Academy of Sciences

  • Qizhi Li

    • Peking university

  • Shilong Zhang

    • Peking university

  • Xiaoli Dong

    • Chinese Academy of Sciences

  • Yao Wang

    • Clemson University
    • clemson university
    • Department of Physics and Astronomy, Clemson University

  • Cheng-Chien Chen

    • University of Alabama at Birmingham

  • Thorsten Schmitt

    • Paul Scherrer Institute
    • PSI
    • Photon Science Division, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland
    • Paul Scherrer Institut

  • Yingying Peng

    • Peking university
    • Peking University