Title:Topology, Entanglement, and Emergent Symmetry in Quantum Critical Spin Chains

Speaker: ZHANG Long，Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences

Time:2024-12-4 10：00  

Venue: C302，New Science Building

Abstract:In this talk, I will introduce our recent works on quantum critical spin chains. In the first part, we focus on the “symmetry-enriched” quantum critical states or gapless symmetry-protected topological states, which cannot be smoothly deformed into each other without either crossing a multicritical point or explicitly breaking certain symmetries even if they belong to the same universality class. We propose that the conformal boundary condition (b.c.) is a generic characteristic of such quantum critical states, and substantiate this proposal with the universal boundary critical behavior, the energy and entanglement spectra of two classes of quantum critical spin chains. Thereby, we establish a novel bulk-boundary correspondence of quantum critical states. We will also discuss its consequence on the finite-entanglement scaling form in matrix product states. In the second part, we study a spin chain model of the domain wall of Z2 topological orders and analytically demonstrate an emergent non-Abelian symmetry at its topological quantum critical point.

Bio:Long Zhang obtained his Ph.D. in physics from Tsinghua University in 2015. After two years as a postdoctoral fellow in Peking University, he joined the faculty of Kavli Institute for Theoretical Sciences, University of Chinese Academy of Sciences in 2017. His research focuses on the theory of correlated electron systems and quantum phase transitions.