Intrinsic electron-doping in nominal "non-doped" superconducting (La,Y)$_2$CuO$_4$ thin films grown by dc magnetron sputtering

TL;DR

This study demonstrates that nominally non-doped La,Y)$_2$CuO$_4$ thin films exhibit intrinsic electron doping, leading to superconductivity with a T_c0 over 13K, similar to doped cuprates, due to oxygen deficiency.

Contribution

It reveals that non-doped LYCO thin films are intrinsically electron-doped, challenging previous band superconductor hypotheses and highlighting oxygen deficiency as the doping mechanism.

Findings

Superconductivity with T_c0 > 13K achieved in LYCO films.

Normal state resistivity and Hall effect indicate electron doping.

Oxygen deficiency induces charge carriers, not band doping.

Abstract

The superconducting nominal "non-doped" $La_{1.85}Y_{0.15}CuO_4$ (LYCO) thin films are successfully prepared by dc magnetron-sputtering and in situ post-annealing in vacuum. The best $T_{C0}$ more than 13K is achieved in the optimal LYCO films with highly pure c-axis oriented T'-type structure. In the normal state, the quasi-quadratic temperature dependence of resistivity, the negative Hall coefficient and effect of oxygen content in the films are quite similar to the typical Ce-doped T'-214 cuprates, suggesting that T'-LYCO shows the electron-doping nature like known n-type cuprates, and is not a band superconductor as proposed previously. The charge carriers are considered to be induced by oxygen deficiency.