Kagome Metals and Superconductors - A “Basket” Full of Novel Correlated and Topological Matter
by
N122 Smart Classroom, 张江校区李政道研究所实验楼
Transition-metal kagome lattice materials provide an exciting platform for correlated and topological quantum states of matter across the full spectrum of correlation and topology. The field has leapt forward upon the discovery of superconductivity in the new family of vanadium-based, nonmagnetic kagome superconductors AV3Sb5 (A=K, Cs, Rb). We discuss the rapid experimental discoveries, focusing on evidence for time-reversal symmetry breaking charge density wave (CDW) order in the normal state, pair density wave (PDW) order in the superconducting state, and unprecedented charge-4e and charge-6e flux quantization above the zero-resistance superconducting state. We argue that the essential phenomenology can be captured by a staggered loop-current CDW order, realizable in models with extended Coulomb interactions, which gives rise to a Chern metal with a partially occupied Chern band and Chern Fermi pockets carrying concentrated Berry curvature. Cooper pairing over the Chern Fermi pockets produces a novel roton PDW state characterized by an emergent vortex-antivortex lattice of loop-supercurrents. The roton PDW enables a plethora of intertwined and vestigial ordered states, including chiral loop-current pseudogap phases and higher-charge superconductivity via staged melting, which will be discussed in connection to recent experimental observations.
Ziqiang Wang graduated from Tsinghua University in 1984. He went to graduate school as a student in the CUSPEA program of Professor T. D. Lee and received the 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 where he has served on the faculty since 1996. He received a Cottrell Scholar Award in 1996 and a SEED Award in 2021 from Research Corporation for Science Advancement. His research focuses on the basic physics of correlated electrons in advanced quantum materials, including Mott-Hubbard systems, unconventional superconductors, and quantum magnets. His recent interests are correlated and topological states, including intrinsic topological superconductors and other novel forms of superconducting matter, Chern metals with partially filled Chern bands, and topological insulators. He is a fellow of the American Physical Society.
Tencent meeting link: https://meeting.tencent.com/dm/J8ArrIU4xD7v Meeting ID: 386 597 713
