时间: 2024年5月22日（周三）下午16:00-17:30

Time: 16:00-17:30 PM, Wednesday, May 22th, 2024

主持人：西湖大学理学院吴从军讲席教授

Host: Chair Professor Congjun Wu, School of Science, Westlake University

地点:  西湖大学云谷校区E10-212

Venue: E10-212, Yungu Campus

报告语言: 英文

Lecture Language: English

Speaker:

Prof. Fan Yang, 

School of Physics, Beijing Institute of Technology

主讲人/Speaker:

Dr. Fan Yang is a professor of physics at the Beijing Institute of Technology. He obtained his Ph.D. in physics from Peking University in 2002 and afterwards became a postdoctoral researcher at the Institute of Advanced Study in Tsinghua University. He joined the Beijing Institute of Technology in 2004 and was promoted to full professor in 2013. Dr. Yang's research area is theoretical strongly-correlated systems and superconductivity. He has contributed to research areas including high-temperature cuprate superconductors, iron-based superconductors, twisted-bilayer graphene, and the quantum spin liquid. Dr. Yang has published over 70 papers, with over 2500 citations.

讲座摘要/Abstract:

Recently, the bilayer perovskite nickelate La3Ni2O7 has been reported to show evidence of high-temperature superconductivity (SC) under a moderate pressure of about 14 GPa. To investigate the superconducting mechanism, pairing symmetry, and the role of apical-oxygen deficiencies in this material, we perform a random-phase-approximation based study on a bilayer model consisting of the $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals of Ni atoms in both the pristine crystal and the crystal with apical-oxygen deficiencies. Our analysis reveals an s+- wave pairing symmetry driven by spin fluctuations. The crucial role of pressure lies in that it induces the emergence of the $\gamma$-pocket, which is involved in the strongest Fermi-surface nesting. We further found the emergence of local moments in the vicinity of apical-oxygen deficiencies, which significantly suppresses the TC. Therefore, it is possible to significantly enhance the TC by eliminating oxygen deficiencies during the synthesis of the samples.

讲座联系人/Contact:

理学院，朱老师，zhuyi48@westlake.edu.cn

School of Science, Ms. Zhu, zhuyi48@westlake.edu.cn