Granovskii-Zhedanov Scars of XYZ Models: Modern Algebraic Perspectives and Realization in Higher Dimensional Lattices

TL;DR

This paper explores the algebraic structure of Granovskii-Zhedanov scars in XYZ models, extending understanding through group theory, perturbation, and numerical optimization, and investigates their realization in higher-dimensional lattices.

Contribution

It introduces new algebraic approaches to analyze GZ scars, including perturbative extrapolation, direct construction, and numerical optimization of the spectrum-generating algebra.

Findings

GZ scars can be described using spectrum-generating algebra in the XXZ limit.

Optimized SGA generators are local operators on two sites for most q-values.

Lattice-independent GZ scars are possible only in specific uniform and non-uniform lattices.

Abstract

In a work by Granovskii and Zhedanov, a surprising family of scar states exhibiting zero entanglement was discovered in the XYZ spin chain, remarkably, nearly three decades before the concept of many-body scars became a subject of active research. Despite its significance, these states have largely gone unnoticed within the physics community. In this study, we uncover the origin of the family of Granovskii-Zhedanov (GZ) scars within the framework of the modern algebraic understanding of quantum many-body scars. We demonstrate that the scar subspace can be effectively described using the spectrum-generating algebra (SGA) framework, as well as through a group-theoretical formulation of the XXZ Hamiltonian. This description, however, is strictly applicable only in the XXZ limit, where a quasi-U(1) symmetry exists within the scar subspace. In contrast, the absence of such quasi-U(1) symmetry in the GZ scar subspace restricts the direct applicability of these standard formulations. To address this, we adopt three alternative approaches. First, we perturbatively extrapolate an approximate SGA for the XYZ system from the XXZ system. Second, we construct the standard SGA directly from the GZ states in the XYZ limit. In the third approach, we numerically optimize the SGA generator and demonstrate that, apart from special q-values, the optimized generator is a local operator with support on two nearest-neighbor sites. Employing these algebraic constructions, we identify the scar subspaces of the XXZ and XYZ systems and clarify their interrelationships. We further explore the possibility of constructing lattice-independent GZ scars in higher-dimensional uniform spin-exchange systems with centrosymmetry, using graphical rules developed for GZ scar construction. Our results indicate that lattice-independent GZ scars can only be supported for specific spatially uniform and non-uniform lattices.