Topological order in a correlated three-dimensional topological insulator

TL;DR

This paper theoretically explores a three-dimensional topological insulator with strong correlations, revealing a novel topologically ordered phase with unique quantum properties and potential experimental realizations.

Contribution

It introduces a new fermionic symmetry-enriched topological phase in correlated 3D insulators with detailed effective field theory and model calculations.

Findings

Identifies a fully gapped, topologically ordered state with eight-fold degeneracy.

Describes a quantized magnetoelectric response and nontrivial braiding statistics.

Provides a specific lattice model realization on the pyrochlore lattice.

Abstract

Motivated by experimental progress in the growth of heavy transition metal oxides, we theoretically study a class of lattice models of interacting fermions with strong spin-orbit coupling. Focusing on interactions of intermediate strength, we derive a low-energy effective field theory for a fully gapped, topologically ordered, fractionalized state with an eight-fold ground-state degeneracy. This state is a fermionic symmetry-enriched topological phase with particle-number conservation and time-reversal symmetry. The topological terms in the effective field theory describe a quantized magnetoelectric response and nontrivial mutual braiding statistics of dynamical extended vortex loops with emergent fermions in the bulk. We explicitly compute the expected mutual statistics in a specific model on the pyrochlore lattice within a slave-particle mean-field theory. We argue that our model also provides a possible condensed-matter realization of oblique confinement.