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Abstract:
We report an Fe K-edge resonant inelastic x-ray scattering study of K0.83Fe1.53Se2. This material is an insulator, unlike many parent compounds of iron-based superconductors. We found a sharp excitation around 1 eV, which is resonantly enhanced when the incident photon energy is tuned near the pre-edge region of the absorption spectrum. The spectral weight and lineshape of this excitation exhibit clear momentum dependence. In addition, we observe momentum-independent broad interband transitions at higher excitation energies of 3-7 eV. Calculations based on a 70-band dp orbital model, using a moderate U-eff approximate to 2.5 eV, indicate that the similar to 1 eV feature originates from the correlated Fe 3d electrons, with a dominant d(xz) and d(yz) orbital character. We find that a moderate U-eff yields a satisfying agreement with the experimental spectra, suggesting that the electron correlations in the insulating and metallic iron-based superconductors are comparable.
