Genuine Phase Diagram of Homogeneously Doped CuO2 Plane in High-Tc Cuprate Superconductors

TL;DR

This study presents a detailed phase diagram of high-Tc cuprate superconductors, revealing the relationship between antiferromagnetism, superconductivity, and doping levels, highlighting the role of AFM interactions in high Tc.

Contribution

It provides a disorder-free phase diagram based on local hole density, clarifying the coexistence and transitions of phases in high-Tc cuprates, which was previously unclear.

Findings

AFMM is stable up to N_h=0.17

Superconductivity coexists with AFMM below N_h=0.17

Maximum Tc occurs near a quantum critical point at N_h=0.15

Abstract

We report a genuine phase diagram for a disorder-free CuO_2 plane based on the precise evaluation of the local hole density (N_h) by site-selective Cu-NMR studies on five-layered high-Tc cuprates. It has been unraveled that (1) the antiferromagnetic metallic state (AFMM) is robust up to N_h=0.17, (2) the uniformly mixed phase of superconductivity (SC) and AFMM is realized at N_h< 0.17, (3) the tetracritical point for the AFMM/(AFMM+SC)/SC/PM(Paramagnetism) phases may be present at N_h=0.15 and T=75 K, (4) Tc is maximum close to a quantum critical point (QCP) at which the AFM order collapses, suggesting the intimate relationship between the high-Tc SC and the AFM order. The results presented here strongly suggest that the AFM interaction plays the vital role as the glue for the Cooper pairs, which will lead us to a genuine understanding of why the Tc of cuprate superconductors is so high.