Scar-induced imbalance in staggered Rydberg ladders

We demonstrate that the kinematically-constrained model of Rydberg atoms on a two-leg ladder with staggered detuning, $\mathrm{\Delta }\in [0,1]$, 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 Néel and Rydberg vacuum initial states around $\mathrm{\Delta }=1$. 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 Néel 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 $\mathrm{\Delta }\sim 1$ from those in the PXP chain. Finally, we identify additional exact mid-spectrum zero modes that stay unchanged as a function of $\mathrm{\Delta }$ and violate ETH.