Quantum Critical Phenomena and the Crystal Structure in Yb-based heavy fermion system

我们研究了Yb基重费米子化合物YbAlB4，它是常压下混合价系统和80mK超导相变中量子临界的例子。我们对量子临界点(QCP)附近超导态的压力-温度相图、压致磁序以及加压下的晶体结构的研究为Yb基重费米子超导系统在QCP附近得到了一个重要的结果。特别地，超导态是孤立存在的，没有连接磁序，通常情况下，Yb基重费米子系统的量子临界性靠近通过加压稳定的磁序。此外，这种被超导态隐藏的非费米液体对压力具有很强的抵抗力。这是我们所知的。但是，人们认为这种Yb材料表现出一种新型的超导电性和非传统的量子临界性。

We study the Yb based heavy fermion compounds, YbAlB4, which is example of quantum criticality in a mixed-valence system at ambient pressure and superconducting transition at 80mK. Our investigation for the pressure vs temperature phase diagram for the superconducting state near quantum critical point (QCP), a pressure-induced magnetic order, and crystal structure under pressure lead to an important result for the Yb based heavy fermion superconducting system near QCP.Specially, the superconducting state is isolated and exists without connecting magnetic order where Normally, quantum criticality of an Yb-based heavy fermion system is found next to a magnetic order stabilized by application of pressure.Moreover, this non-Fermi liquid hidden by the superconducting state is robust against the pressure. which is ever known at all. But, it is thought that this Yb material exhibits a new type superconductivity and a unconventional quantum criticality.