SPring-8, the large synchrotron radiation facility

Date&Time: June 3, 16:00-17:30

Speaker: Prof. T. Moriya (Honorary Professor)
Affiliation: Tokyo University of Science

Abstract
　　High-Tc cuprates are hole or electron-doped Mott insulators. Superconductivity is considered to appear around the antiferromagnetic instability or quantum critical point(QCP). The problem is to give a consistent explanation for the superconducting state with high Tc and anomalous normal state properties. There are two major streams of theoretical investigations, one emphasizing closeness to Mott insulators and the other emphasizing closeness to antiferromagnetic QCP. The starting model is common, the Hubbard or d-p model which are now widely believed to contain most essential physics of the problem. The former approach approximates them with the t-J model while the latter makes use of the spin fluctuation theory around the QCP. Their ranges of applicability in the parameter space of the model scarecely overlap with each other. We deduce the position of the high-Tc cuprates in this parameter space from several experimental results and compare it with the teritories of the above two approaches. With the result of this comparison in mind we review briefly on the present status of the theoretical understandings of the subject with emphasis on the latter approach; we discuss to what extent the experimental results of fundamental importance are explained theoretically.