The emergence and disappearance of high Tc superconductivity in cuprates

Abstract:

The mechanism of high temperature cuprates superconductivity remains an outstanding puzzle despite 30 years of research. A key task in unveiling this mystery is to understand the electronic structure evolution from the doped Mott insulator perspective. In this talk, we report scanning tunneling microscopy studies of the atomic electronic structure of cuprates with increasing doping levels. We first discuss the charge transfer gap in the parent Mott insulator, and its anticorrelation with the maximum transition temperature, implying the central role of superexchange interaction in mediating the Cooper pairing. We then show how the low energy electronic states emerge within the charge transfer gap when few holes are introduced, which can be regarded as hydrogen atom and molecule in a Mott insulator background. The doped few percent of holes self-assemble into small islands of checkerboard. Even in the insulating sample, we observe a small superconducting-like gap when approaching the checkerboard island. Across the insulator to superconductor transition, we observe the enhancement of quasiparticle interferences characteristic of long-range phase coherence. We find that each checkerboard puddle contains approximately two holes, and exhibits stripy internal patterns that have strong influence on the superconducting properties. With further increase of doping into the overdoped regime, the strong quasiparticle scattering in the antinodal region causes pair breaking, which is the driving force for the vanishing of superconductivity.

Bio:

王亚愚，1998年本科毕业于中国科技大学物理系，2004年在美国普林斯顿大学物理系获得博士学位，2004年至2007年在美国加州大学伯克利分校物理系任Miller Research Fellow，2007年加入清华大学物理系任教授至今。研究领域为凝聚态物理实验，近期的主要研究方向为拓扑量子材料的输运性质和高温超导体的扫描隧道显微学研究。曾获得William McMillan Award、“马丁-伍德爵士中国奖”、中国物理学会“黄昆物理奖”、国家自然科学一等奖（第二完成人）、腾讯“科学探索奖”、入选新基石研究员。