Unusual interplay between magnetism and superconductivity in CeAu2Si2 under pressure
High pressure provides a powerful means for exploring the unconventional superconductivity which emerges mostly on the border of magnetism. In this talk, I will present the discovery of pressure-induced heavy-fermion superconductivity up to 2.5 K in the antiferromagnet CeAu2Si2 (TN ≈10 K). Remarkably, it is found that the magnetic and superconducting phases overlap across an unprecedentedly wide pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk Tc and TM are strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. Tc reaches a maximum of 2.5 K at a pressure slightly below pc ≈ 22.5 GPa, where magnetic order disappears. Around pc, the depression of Tc with the increase of the residual resistivity can be well understood in terms of pair breaking by nonmagnetic disorder, strongly suggesting an unconventional pairing state. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce-4f electrons associated with a critical end point lying just above pc. Dynamical mean-field theory calculations suggest that the peculiar behavior in pressurized CeAu2Si2 in comparison with CeCu2Si2 and CeCu2Ge2 might be related to its Ce-4f orbital occupancy.
Reference: Z. Ren et al., PRX 4, 031055 (2014); PRB 91, 094515 (2015).
任之于2009年6月获浙江大学凝聚态物理博士，随后在日本大阪大学和瑞士日内瓦大学从事博士后研究，2017年3月任浙江西湖高等研究院助理教授。研究领域包括拓扑量子材料和非常规超导体。共发表文章45篇，总计被引用超过3400次，Hirsh h-因子为28。部分成果被APS Physics Synopsis和Nature Physics News and Views以亮点进行报道。2011百篇优秀博士论文提名奖，2012年教育部高校自然科学一等奖(排名第五)。