报告题目：Extraordinary electronic matter

报  告  人：Ziqiang Wang, Boston College

报告时间：2025年2月27日16：30

报告地点：物理楼（附中南侧）W101

内容摘要：In ordinary superconductors, an external magnetic field is needed to generate magnetic vortices. We discuss two examples where this conventional folklore breaks down in a fundamental way.  The first example is superconductors with strong spin-orbit coupling. We show that topological defect excitations, dubbed quantum anomalous vortices (QAV), can nucleate around magnetic ions spontaneously in the absence of external magnetic fields. When such superconductors possess a Z 2 nontrivial band structure and superconducting topological surface states, as do certain Fe-based superconductors, the magnetic impurity induced QAV are nonabelian and host Majorana zero mode (MZM) in the vortex core. Recent experimental observations of QAV and MZM will be discussed. The second example concerns the newly emerged kagome superconductors AV3Sb5 (A=K, Cs, Rb) that exhibit a cascade of correlated and topological quantum states. We discuss recent experimental evidence for time-reversal symmetry breaking in both the normal and the superconducting state. We argue that the essential phenomenology can be captured by an unconventional charge density wave (CDW) with loop current order. This leads to a Chern metal with a partially filled Chern band and Chern Fermi pockets carrying concentrated Berry curvature. We show how Cooper pairing over the Chern Fermi pockets produces a novel roton superconductor, where the internal phases of three pairing components are locked at 120-degrees and loop supercurrents circulate around an emergent vortex-antivortex lattice with pair density modulations. We discuss extraordinary properties of this chiral topological superconductor and the plausible charge-6e superconductivity in connection to the experimental observation of charge-6e flux quantization.

报告人简介：Ziqiang Wang graduated from Tsinghua University in 1984 and received his Ph.D. degree in Physics from Columbia University in 1989. He was a postdoc fellow at Rutgers University and Los Alamos National Laboratory, and became an assistant professor at Boston University in 1993. He is currently a professor in the Physics Department at Boston College. He received a Cottrell Scholar Award in 1996 and a SEED Award in 2021 from Research Corporation for Science Advancement. He is an elected fellow of the American Physical Society.