Cu-spin Correlation in the Electron-overdoped High-Tc Cuprate Thin Films of La_2-x_Ce_x_CuO_4_ Probed by Low-energy Muons

TL;DR

This study investigates Cu-spin correlations in electron-overdoped La_2-x_Ce_x_CuO_4_ thin films using low-energy muons, revealing correlations that develop at low temperatures even when superconductivity is suppressed, contrasting with hole-doped cuprates.

Contribution

It provides new insights into Cu-spin correlations in electron-overdoped cuprates, highlighting differences from hole-doped counterparts and suggesting possible links to antiferromagnetism or ferromagnetism.

Findings

Cu-spin correlation develops at low temperatures in overdoped films.

Correlations persist even when superconductivity is suppressed.

Results contrast with behavior in hole-doped high-Tc cuprates.

Abstract

We investigated the Cu-spin correlation in the overdoped regime of the electron-doped high-Tc cuprate thin films of La_2-x_Ce_x_CuO_4_, changing the reduction condition from muon spin relaxation using low-energy muons. The Cu-spin correlation developed at low temperatures for optimally reduced films with x=0.13 as well as x=0.17 where the superconductivity was almost suppressed. These results are contrary to those observed in the hole-doped high-Tc cuprates where the development of the antiferromagnetic Cu-spin correlation disappears together with the suppression of superconductivity. The Cu-spin correlation developed at low temperatures in x=0.17 may be understood in terms of antiferromagnetism, but it may be related to a ferromagnetic order recently suggested in the nonsuperconducting heavily overdoped La$_2-x_Ce_x_CuO_4_ with x~0.18.