Genuine Phase Diagram of Homogeneously Doped CuO_2 Plane in High-T_c Cuprate Superconductors(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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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-T_c 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≈75K, (4) T_c is maximum close to a quantum critical point (QCP) at which the AFM order collapses, suggesting the intimate relationship between the high-T_c, 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 T_c of cuprate superconductors is so high.
社団法人日本物理学会の論文
2008-12-15