高等研究中心杰出学人讲座：高温超导体实验专题

报告人：崔章琪（Chang-Chyi Tsuei）

报告一：d-wave pairing symmetry and its implications for understanding HTS，

时间：2006年10月16日（星期一）下午3:30，

地点：清华大学高等研究中心地下报告厅

报告二：Fluctuating Cu-O-Cu bond model for HTS in cuprates，

时间：2006年10月17日（星期二）下午3:30，

地点：清华大学高等研究中心地下报告厅

报告人简介

崔章琪：著名实验物理学家。最先从实验上确认铜氧化物高温超导体的d波配对特性。1992年获Max Planck研究奖，1998年获美国物理学会Barkley凝聚态物理奖，2000年获IBM合作奖。1966年在美国加州理工学院 (Caltech) 取得博士学位，随后在该校任教职。1973年加入IBM公司Watson研究中心。现任该中心超导研究计划主持人。

报告摘要

Talk I：Determination and consequences of d-wave pairing symmetry in cuprate superconductors: the road to d-wave and beyond

The recent development of phase-sensitive techniques has finally settled the decade-long d-wave versus s-wave debate in  favor of an  order parameter with d x2- y2   symmetry in various cuprate superconductors. We will briefly review the experiments using the half-flux-quantum effect as a definitive signature for d-wave pairing symmetry. In particular, a series of recent tricrystal experiments will be presented to demonstrate that the d-wave pair state in this class of superconductors is robust against time reversal symmetry breaking, and a wide-range of temperature and doping variations. We will discuss the consequences of establishing the d-wave pair state for the nature of the superconducting ground state and its low energy excitations in high temperature superconductors.   Also will be addressed is the question of whether unconventional (d-wave) superconductivity (pairing mechanism, isotope effect, nm-scale charge inhomogeneity…) can be understood in terms of conventional wisdom, the Fermi-liquid based BCS theory.

Talk II：Fluctuating Cu-O-Cu Bond Model of High-Temperature Superconductivity

An order parameter with d-wave symmetry is well-established in various cuprate superconductors. Building on the insight gained from this knowledge of pairing symmetry, a new model of high temperature superconductivity (HTS) has been developed. This HTS model is based on the observation that the charge carrier motion along the in-plane Cu-O-Cu bond must be non-linearly modulated by the oxygen vibrational degrees of freedom, enabling d-wave pairing mediated by an anharmonic two-(local) phonon process. This new pairing mechanism, decoupled from the large on-site Coulomb repulsion, is qualitatively different from the conventional one-phonon BCS pairing interaction. The resulting fluctuating bond model provides a natural explanation of such characteristic features of high-temperature superconductors as d-wave pairing, d-wave pseudogap, the doping dependence of Tc, of T*, and of the isotope shift, and also the recently observed nanoscale spatial gap inhomogeneity.