Universal time evolution of string order parameter in quantum critical systems with boundary invertible or noninvertible symmetry breaking
Year: 2025
Type: article
Abstract: The global symmetry, either invertible or noninvertible, has been extensively studied in two-dimensional conformal field theories in recent years. When the theory is defined on a manifold with open boundaries, however, many interesting conformal boundary conditions will fully or partially break such global symmetry. In this work, we study the effect of symmetry-breaking boundaries or interfaces when the system is out of equilibrium. We show that the boundary or interface symmetry breaking can be detected by the time evolution of string order parameters, which are constructed from the symmetry operators that implement the symmetry transformations. While the string order parameters are independent of time if the symmetry is preserved over the whole system, they evolve in time in a universal way if the boundary or interface breaks the symmetry. More explicitly, in the presence of boundary or interface symmetry breaking, the string order parameters decay exponentially in time after a global quantum quench, and decay as a power law in time after a local quantum quench. We also generalize our study to the case when the string order parameters are defined in a subsystem, which are related to the full counting statistics. It is found there are also universal features in the time evolution of string order parameters in this case. We verify our field-theory results by studying the time evolution of these two different types of string order parameters in lattice models.
Authors: Ruhanshi Barad, Qicheng Tang, Wei Zhu, Xueda Wen
Institutions: Georgia Institute of Technology, Westlake University
Language: English
Topic: Quantum many-body systems
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G2998044070, G8959834147
OpenAlex ID: W4409412527