[Joint CQSE & NCTS Seminar] Dissipation-Induced Criticality and Nonequilibrium Topology

Title: [Joint CQSE & NCTS Seminar] Dissipation-Induced Criticality and Nonequilibrium Topology
Speaker: Dr. Christopher Yang (University of California, Irvine)​​​​​​​
Time: 2026/5/15 (Fri.) 14:30-15:30
Place: NCTS Physics Lecture Hall, 4F, Chee-Chun Leung Cosmology Hall, NTU
Online: https://nationaltaiwanuniversity-zbh.my.webex.com/nationaltaiwanuniversity-zbh.my/j.php?MTID=madb2c3b9d23a56faace3593823ecfdee
 

Abstract
Quantum systems can now be designed with unprecedented precision, making it possible to design complex phases of matter and highly entangled states for quantum platforms. Yet realistic quantum systems are never perfectly isolated. This raises a fundamental question: what kinds of quantum matter can be prepared in the presence of dissipation, and can such states be intrinsically interesting? In this talk, I will present two examples in which dissipation does not merely preserve exotic quantum phases, but actively helps create them. The first is a highly entangled critical phase governed by a complex conformal field theory [1]. We show that a broad class of non-Hermitian 1+1D quantum systems with O(N) symmetry flows to this new universality class, which hosts an emergent, dissipation-induced non-invertible symmetry. The second is a light-induced topological phase stabilized over ultralong timescales. In this setting, dissipation addresses longstanding concerns about heating and the stability of strongly driven Floquet phases, which otherwise survive only on femto to picosecond timescales. Dissipative dynamics not only stabilize light-induced topological states, but also enable controllable many-body responses, including a tunable anomalous Hall effect in twisted bilayer graphene [2], a quantized nonadiabatic charge pump in phonon-driven systems [3], and experimental signatures of Floquet many-body steady states in graphene [4]. Across these examples, dissipation emerges as a remarkable resource for quantum design and control.

[1] CY, T. Scaffidi, “Asymptotic freedom, lost: Complex conformal field theory in the two-dimensional O(N>2) nonlinear sigma model and its realization in the spin-1 Heisenberg chain,” arXiv:2601.02459 (2026)
[2] CY, I. Esin, C. Lewandowski, G. Refael, “Optical Control of Slow Topological Electrons in Moire Materials,” Physical Review Letters 131, 026901 (2023)
[3] CY, W. Hunt, G. Refael, I. Esin, “Quantized Acoustoelectric Floquet Effect in Quantum Nanowires,” Physical Review Letters 133, 226301 (2024)
[4] Y. Liu, CY, et al. “Signatures of Floquet electronic steady states in graphene under continuous-wave mid-infrared irradiation,” Nature Communications, 16, 2057 (2025)
 
Biography
Christopher Yang is the Moore Foundation Postdoctoral Fellow and Eddleman Quantum Institute Postdoctoral Fellow at the Eddleman Quantum Institute, University of California, Irvine. He received his Ph.D. in condensed matter physics from the California Institute of Technology in 2025 as a Department of Energy Computational Science Graduate Fellow, and his B.A. in physics from the University of California, Berkeley in 2020. His research focuses on identifying topological and highly entangled quantum phases of matter in open quantum systems.