# Nature of carrier doping in T'-La1.8-xEu0.2SrxCuO4 studied by X-Ray Photoemission and Absorption Spectroscopy

## TL;DR

This study investigates the doping mechanisms in T'-La1.8-xEu0.2SrxCuO4 superconductors using X-ray spectroscopy, revealing electron and hole doping effects and their relation to the charge-transfer gap.

## Contribution

It provides detailed spectroscopic evidence clarifying how reduction annealing and Sr substitution influence carrier doping in T'-structured cuprates.

## Key findings

- Electrons are doped by reduction annealing.
- Holes are introduced through Sr substitution.
- The system remains electron-doped with a collapsed charge-transfer gap.

## Abstract

Recently, hole-doped superconducting cuprates with the T'-structure La1.8-xEu0.2SrxCuO4 (LESCO) have attracted a lot of attention. We have performed x-ray photoemission and absorption spectroscopy measurements on as-grown and reduced T0-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.