摘要

We performed systematic investigation of various doping approaches and the effects on superconductivity in the recently-discovered FeAs-based superconductors. Main three type doping approaches are presented as below. (1) Superconductivity induced by Th doping in Ln-1111 system and a record of Tc=56 K is reached in Gd1-xThxFeAsO system. (2) Superconductivity induced by doping of Co or Ni on Fe site in both 1111 and 122 systems. A dome –like doping dependence of Tc is observed. The result points to an itinerant picture of 3d electrons in the iron arsenides. We have also observed that a correlation between Tc and normal state thermopower. (3) The doping effect of non-magnetic impurity Zn is investigated and a possible change in the pairing symmetry with doping level is proposed. (4) Chemical pressure is studied by doping of P on As site and chemical pressure induced superconductivity is observed. In P-doped Eu-122, a coexistence of superconductivity and ferromagnetism is observed. In P-doped Ba-122 system, a possible quantum critical point of Fe SDW is evidenced. A rich phase diagram of CeFeAs1-xPxO system is revealed and we suggested that the inter-layer Kondo coupling plays an important role in the rare earth iron pnictides.

报告人简介

许祝安，“国家高层次人才”特聘教授，1988年中国科学技术大学物理系本科毕业，1994年获该校博士学位，1997-2000美国普林斯顿大学访问学者，2000年起浙江大学教授。研究领域：非常规超导电性，强关联电子体系，功能材料。主要成果：利用Nernst效应等测量手段发现高温超导体赝能隙区的超导涨落现象，利用新的掺杂方法获得超导温度达56K的铁基氧砷化合物超导体，获得系列新的铁基超导材料。共发表SCI论文100余篇，其中《Nature》1篇，PRL 6篇。论文被他人引用1000余次。