Interaction Enabled Fractonic Higher-Order Topological Phases

TL;DR

This paper introduces new three-dimensional higher-order topological phases protected by subsystem symmetries, featuring gapless hinge modes and fractonic excitations, expanding understanding of strongly interacting topological matter.

Contribution

It constructs microscopic lattice models of HOSPTs with subsystem symmetry protection and fractonic quasiparticles, without relying on spatial symmetry.

Findings

Existence of HOSPTs with hinge modes protected by subsystem symmetries

Presence of fractonic quasiparticles confined to low-dimensional manifolds

Boundary anomalies indicating non-trivial topological phases

Abstract

In this work, we present a collection of three-dimensional higher-order symmetry protected topological phases (HOSPTs) with gapless hinge modes that exist only in strongly interacting systems subject to subsystem symmetry constraints. We use a coupled wire construction to generate three families of microscopic lattice models: insulators with helical hinge modes, superconductors with chiral Majorana hinge modes, and fractionalized insulators with helical hinge modes that carry fractional charge. In particular, these HOSPTs do not require spatial symmetry protection, but are instead protected by subsystem symmetries, and support "fractonic" quasiparticle excitations that move within only a low-dimensional sub-manifold of the system. We analyze the anomaly structure for the boundary theory and the entanglement Hamiltonian, and show that the side surfaces of these HOSPTs, despite being partially gapped, exhibit symmetry anomalies, and can only be realized as the boundary of three-dimensional HOSPT phases.