Unusual interplay between magnetism and superconductivity in CeAu2Si2 under pressure

报告摘要： High pressure provides a powerful means for exploring the unconventional superconductivity which emerges mostly on the border of magnetism [1]. 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) [2]. 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, at which 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 [3]. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce-4f electrons associated with a critical endpoint lying just above pc. A comparison with CeCu2Si2, CeCu2Ge2, CeAg2Si2 [4] is given, and its implication on the pairing mechanism will be discussed.Reference: [1] G. Knebel et al., C. R. Phys. 12, 542 (2011). [2] Z. Ren et al., Phys. Rev. X 4, 031055 (2014).[3] Z. Ren et al., Phys. Rev. B 91, 094515 (2015).[4] G. W. Scheerer et al., arXiv:1711.02965, Physica B (2017).