Extreme many-body scarring in a quantum spin chain via weak dynamical constraints

It has recently been established that quantum many-body scarring can prevent the thermalization of some isolated quantum systems starting from certain initial states. One of the first models to show this was the socalled PXP Hamiltonian, which was used to theoretically model an experiment on a chain of strongly interacting Rydberg atoms. A defining feature of the PXP Hamiltonian is a set of dynamical constraints that make certain states inaccessible to the dynamics. In this paper we construct a class of spin chain models that are parameterized by a discrete variable l that controls the strength of a dynamical constraint. We show that by increasing l the constraint becomes weaker in the sense that fewer states are excluded from the dynamics. The PXP Hamiltonian is a special case for l = 2. By weakening the constraint to l >= 4, however, we find a more extreme version of quantum scarring than in the PXP Hamiltonian with the number of scar states growing exponentially in the system size.

Automated summary

Recent studies have shown that quantum many-body scarring can hinder the thermalization process of certain isolated quantum systems starting from specific initial states. In this paper, a class of spin chain models parameterized by a discrete variable l is constructed to control the strength of the dynamical constraint. It is found that by increasing the value of l, the constraint becomes weaker, resulting in fewer excluded states during the dynamics. By weakening the constraint to l >= 4, a more extreme version of quantum scarring is observed with an exponential growth of scar states as the system size increases.