X-ray absorption and photoemission spectroscopy of electronic phase separation in Kx Fe2-y Se2

The electronic structure of phase separated KxFe2-ySe2 has been studied by means of x-ray absorption spectroscopy (XAS) and photoemission spectroscopy. Both Fe L2,3-edge XAS and Fe 2p photoemission spectra show a signature of the metallic phase that is embedded in the insulating texture. Valence-band spectra, measured with different excitation energies, reveal a finite density of states at the Fermi level driven by the Fe 3d orbitals. A combined analysis of the Se L2,3-edge and the Se K-edge XAS provides further information on a significant density of states of Se 4p character near the Fermi level, consistent with a large hybridization of these states with the Fe 3d orbitals. The K L2,3-edge XAS spectrum is also presented to show element specific partial density of states. The results are discussed in connection with the electronic phase separation in KxFe2-ySe2 driven by the Fe 3d states.