Title:  Quantum Many-Body Scars and Quantum Criticality

Time:10am Nov. 15, 2021(Beijing time)

Speaker: Zhi-Yuan Yao (Tsinghua)

Zoom Meeting ID：949 559 7503

Password：2021

Meeting URL:

https://us06web.zoom.us/j/9495597503?pwd=UFVMUUVxb3pDUHRkWEFQY3MzRjJYUT09

Abstract:  

Recent experimental observations of unexpected long-lived oscillations of local observables in Rydberg atom chains have revealed that the strong eigenstate thermalization hypothesis (ETH) can break down. This has later been attributed to a set of ETH-violating eigenstates, the quantum many-body scar states (QMBS), embedded in the thermal continuum of the approximated PXP model. Despite many good approximations, the nature of the QMBS in the PXP model remains unclear. We study a deformed PXP model with an external magnetic field that exhibits both quantum scar states and quantum criticality. Although the former involves the properties of generic excited states and the latter concerns the low-energy physics, we discover two surprising connections between them. First, we show that the quantum many-body scar states can be tracked to a set of quantum critical states, whose nature can be understood as pair-wisely occupied Fermi sea states. Second, we show that the partial violation of quantum thermalization diminishes in the quantum critical regime. 

About the speaker：

Zhiyuan Yao is a C. N. Yang postdoctoral fellow at Institute for Advanced Study (IAS), Tsinghua University. He obtained his Ph.D. in physics in 2018 from University of Massachusetts, Amherst under the supervision of Nikolay Prokof'ev and Boris Svistunov. His Ph.D. study focuses on quantum Monte Carlo and theoretical studies of quantum phase transitions in disordered boson systems. After joining IAS, Tsinghua University, his research interests has been mainly motivated by novel phenomena in cold-atom experiments, in particular problems related to thermalization and lattice gauge theory.