Abstract
Iron chalcogenide superconductors are multiorbital materials with strong electron correlations. Here we use angle-resolved photoemission spectroscopy to study orbital dependent correlation effects in single-layer , an iron chalcogenide superconductor with high interfacial superconductivity, nondegenerate electron pockets, and varied electron correlation compared with single-layer . Signatures of polaronic behavior are observed over the whole temperature range, suggesting electron-boson interactions. Moreover, the nondegeneracy of the electron bands helps to resolve the temperature dependent evolution of different bands. The coherent spectral weight of one electron band significantly decreases above 115 K and is completely depleted at 200 K while that of the other one remains finite, giving direct evidence of an orbital selective Mott crossover. Correspondingly, the weight of the incoherent photoemission spectra is enhanced, indicating a coherent-incoherent crossover during the Mott crossover process. Compared with that in single-layer , the depletion temperature of the band is higher in single-layer due to the decreased correlation of the band in . These phenomena help to construct a more complete picture of electron correlations in the FeSe family.
- Received 21 April 2016
- Revised 16 August 2016
DOI:https://doi.org/10.1103/PhysRevB.94.115146
©2016 American Physical Society