Speaker: Jiabin Yu (Princeton University)

Host: Rebecca Flint

Title: Band geometry and topology in correlated quantum materials

Abstract: Band geometry (or quantum geometry) and band topology describe, respectively, the local and global properties of Bloch electron wavefunctions in quantum materials. These concepts have already triggered a revolution in quantum materials based on single-particle physics, but their significance in interacting systems is much less explored. In this talk, I will discuss two recent advances in this direction for the two major interactions in solids: electron-phonon interaction and electron-electron Coulomb interaction. First, I will explain how band geometry contributes crucially to the electron-phonon interaction, potentially offering a new design principle for higher-temperature superconductors. Second, we show that band topology and band mixing are key to explaining various experimental puzzles centered around fractional Chern insulators (FCIs), which were recently observed in twisted MoTe₂ and graphene-hBN superlattices. FCIs, the zero-field analogs of the fractional quantum Hall effect, are induced by the Coulomb interaction in fractionally filled, (nearly-)flat topological bands, and their discovery heralds the discovery of more exotic topologically ordered phases, which will be discussed.

Bio: Dr. Jiabin Yu received his Ph.D. in physics from the Pennsylvania State University, University Park, in 2020, under the supervision of Prof. Chao-Xing Liu. He then spent two years as a postdoctoral fellow at the Condensed Matter Theory Center at the University of Maryland, College Park, primarily working with Prof. Sankar Das Sarma. He is currently a Moore postdoctoral fellow at Princeton University, working in close collaboration with Prof. B. Andrei Bernevig since September 2022. His research focuses on twisted/moiré materials, band geometry/topology, unconventional superconductivity, response theory/quantum field theory, and dynamical quantum phases of matter.