Scar-induced imbalance in staggered Rydberg ladders

TL;DR

This paper uncovers quantum many-body scars in a two-leg ladder Rydberg atom model with staggered detuning, revealing non-thermalizing dynamics and eigenstate properties that extend the PXP model to a ladder geometry.

Contribution

It introduces a non-perturbative ladder model with QMBS, demonstrating coherent revivals, ETH violation, and exact zero modes, expanding understanding of scar phenomena beyond chains.

Findings

QMBS cause revivals and site-dependent magnetization dynamics.

Eigenstate thermalization hypothesis is violated at long times.

Exact zero-energy modes are identified that are invariant with detuning.

Abstract

We demonstrate that the kinematically-constrained model of Rydberg atoms on a two-leg ladder with staggered detuning, $\Delta \in [0,1]$, has quantum many-body scars (QMBS) in its spectrum and represents a non-perturbative generalization of the paradigmatic PXP model defined on a chain. We show that these QMBS result in coherent many-body revivals and site-dependent magnetization dynamics for both N\'eel and Rydberg vacuum initial states around $\Delta=1$. The latter feature leads to eigenstate thermalization hypothesis (ETH)-violating finite imbalance at long times in a disorder-free system. This is further demonstrated by constructing appropriate local imbalance operators that display nonzero long-time averages for N\'eel and vacuum initial states. We also study the fidelity and Shannon entropy for such dynamics which, along with the presence of long-time finite imbalance, brings out the qualitatively different nature of QMBS in PXP ladders with $\Delta \sim 1$ from those in the PXP chain. Finally, we identify additional exact mid-spectrum zero modes that stay unchanged as a function of $\Delta$ and violate ETH.