Nature of Carrier Doping in T'-La1.8-xEu0.2SrxCuO4 Studied by X-Ray Photoemission and Absorption Spectroscopy

Recently, hole-doped superconducting cuprates with the T'-structure La_1.8-xEu_0.2Sr_xCuO₄ (LESCO) have attracted a lot of attention. We have performed x-ray photoemission and absorption spectroscopy measurements on as-grown and reduced T'-LESCO. Results show that electrons and holes were doped by reduction annealing and Sr substitution, respectively. However, it is shown that the system remains on the electron-doped side of the Mott insulator or that the charge-transfer gap is collapsed in the parent compound.