Disorder-Free Localization and Many-Body Quantum Scars from Magnetic Frustration

TL;DR

This paper demonstrates that magnetic frustration can naturally produce models with disorder-free localization and quantum many-body scars, leading to anomalous thermalization in high energy states of non-integrable systems.

Contribution

It introduces three classes of frustrated spin models that exhibit disorder-free localization and quantum many-body scars, expanding understanding of thermalization breakdown due to frustration.

Findings

Certain frustrated models show inhibited information propagation.

Models exhibit eigenstates with low entanglement entropy.

Frustration enables systematic construction of non-thermalizing systems.

Abstract

The concept of geometrical frustration has led to rich insights into condensed matter physics, especially as a mechansim to produce exotic low energy states of matter. Here we show that frustration provides a natural vehicle to generate models exhibiting anomalous thermalization of various types within high energy states. We consider three classes of non-integrable frustrated spin models: (I) systems with local conserved quantities where the number of symmetry sectors grows exponentially with the system size but more slowly than the Hilbert space dimension, (II) systems with exact eigenstates that are singlet coverings, and (III) flat band systems hosting magnon crystals. We argue that several 1D and 2D models from class (I) exhibit disorder-free localization in high energy states so that information propagation is dynamically inhibited on length scales greater than a few lattice spacings. We further show that models of class (II) and (III) exhibit quantum many-body scars -- eigenstates of non-integrable Hamiltonians with finite energy density and anomalously low entanglement entropy. Our results demonstrate that magnetic frustration supplies a means to systematically construct classes of non-integrable models exhibiting anomalous thermalization in mid-spectrum states.