Topological insulators in three dimensions from spontaneous symmetry breaking

TL;DR

This paper introduces a new class of three-dimensional topological insulators arising from spontaneous symmetry breaking in strongly correlated systems, characterized by an order parameter and protected one-dimensional modes.

Contribution

It presents a microscopic model for topological Mott insulators with spontaneous spin-rotation symmetry breaking and identifies their unique topological features.

Findings

Topological Mott insulators possess an order parameter describing symmetry breaking.

Line defects host protected one-dimensional modes.

The phase is characterized as a strong topological insulator with unique bulk-boundary correspondence.

Abstract

We study three dimensional systems where strong repulsion leads to an insulating state via spontaneously generated spin-orbit interactions. We discuss a microscopic model where the resulting state is topological. Such topological `Mott' insulators differ from their band insulator counterparts in that they possess an additional order parameter, a rotation matrix, that describes the spontaneous breaking of spin-rotation symmetry. We show that line defects of this order are associated with protected one dimensional modes in the {\em strong} topological Mott insulator, which provides a bulk characterization of this phase.