Unidirectional subsystem symmetry in a hole-doped honeycomb-lattice Ising magnet

TL;DR

This paper demonstrates a nearly exact unidirectional subsystem symmetry in a hole-doped honeycomb Ising magnet, where single holes are localized but pairs move freely along one direction, revealing a new type of symmetry in quantum materials.

Contribution

It introduces a model showing nearly exact dipole conservation and unidirectional subsystem symmetry in a hole-doped honeycomb lattice, combining numerical and analytical methods.

Findings

Single holes are localized due to symmetry constraints.

Hole pairs (dipoles) can move freely along one direction.

Subsystem symmetry persists at low hole concentrations.

Abstract

We study a model of a hole-doped collinear Ising antiferromagnet on the honeycomb lattice as a route toward the realization of subsystem symmetry. We find nearly exact conservation of dipole symmetry verified both numerically with exact diagonalization (ED) on finite clusters and analytically with perturbation theory. The emergent symmetry forbids the motion of single holes -- or fractons -- but allows hole pairs -- or dipoles -- to move freely along a one-dimensional line, the antiferromagnetic direction, of the system; in the transverse direction, both fractons and dipoles are completely localized. This presents a realization of a `unidirectional' subsystem symmetry. By studying interactions between dipoles, we argue that the subsystem symmetry is likely to continue to persist up to finite (but probably small) hole concentrations.