Time: 15:00 (UTc/GMT+8:00,Beijing/Shanghai), Dec. 11 (Fri.), 2020
Venue: KITS Seminar Room, 4th floor, No. 7 Building, UCAS Zhong-Guan-Cun Campus [View on maps]
Speaker: Prof. Fan Yang (BIT)
Abstract:
The recently revealed superconductivity (SC) in quasicrystalline material has aroused many research interests. Here we focus on several fundamental issues on the SC on the quasicrystal (QC) through studying both negative and positive Hubbard models on the QC Penrose lattice. The first issue is whether the Cooper instability will take place for an infinitesimal attractive or repulsive interaction on the QC. For this issue, we analytically proved the Cooper instability for the negative-U case and numerically revealed the Kohn-Luttinger pairing instability for the positive-U case. We also show that such Cooper pairing can lead to finite superfluid density in the thermal-dynamic limit. The second issue is about the classification of the pairing symmetry, and the properties of each class on the QC. Based on irreducible representations (IRRP) of the D5 point group, our classification reveals two remarkable properties of the pairing states on the QC. Firstly, the spin and spacial angular momenta of a Cooper pair is decorrelated. Secondly, the pairing states belonging to the 2D IRRP of D5 can be topological SCs carrying spontaneous bulk super current and spontaneous vortices. These two remarkable properties are general for the SCs on all QCs, and are rare on periodic lattices.
About the Speaker:
杨帆，北京理工大学物理学院教授。2002年博士毕业于北京大学物理系，2004年清华大学高等研究中心博士后出站，之后加入北理工。主要研究强关联电子系统和超导理论，包括铜氧化物高温超导、铁基超导、在各类实际材料或者模型系统中的非常规超导与拓扑超导，量子自旋液体以及相互作用驱动的拓扑量子态等，获得一系列重要研究结果。
