Nuclear-spin evidence of insulating and antiferromagnetic state of CuO2 planes in superconducting Pr2Ba4Cu7O15-{\delta}

TL;DR

This study provides evidence that CuO2 planes in superconducting Pr2Ba4Cu7O15-{ extdelta} are insulating and antiferromagnetically ordered, revealed through nuclear-spin signals, challenging the typical association of CuO2 planes with metallicity in superconductors.

Contribution

The paper demonstrates that in Pr2Ba4Cu7O15-{ extdelta}, CuO2 planes are insulating and antiferromagnetic despite bulk superconductivity, using nuclear-spin measurements.

Findings

Cu nuclear-spin signals vanish at 2K in CuO2 planes

Plane signals shift to higher frequencies at low temperature

CuO2 planes are insulating and antiferromagnetic in Pr247

Abstract

In contrast to the "Pr-issue" that neither PrBa2Cu3O7 (Pr123) nor PrBa2Cu4O8 (Pr124) shows superconductivity (SC), we have observed 100%-fraction of SC in an oxygen-reduced Pr2Ba4Cu7O(15-delta) (Pr247) which has a hybrid structure that Pr247 = Pr123 + Pr124. It is found that Cu nuclear-spin signals from the CuO2 planes observed at 300K are completely wiped out down at 2K. Instead, plane signals at 2K are observed at higher frequencies. This indicates that, despite the bulk SC, the CuO2 planes in Pr247 are found to be in an insulating and antiferromagnetically ordered state.