Electron Correlation Effects on Topological Phases

TL;DR

This paper explores how electron correlations can induce topological phases like topological Mott insulators and Weyl semimetals, revealing rich phase diagrams and robust domain wall states in pyrochlore materials.

Contribution

It demonstrates the role of electron Coulomb repulsion in generating topological phases and analyzes the properties of magnetic domain walls in pyrochlore iridates.

Findings

Electron correlation can induce topological Mott insulators.

Magnetic domain walls host robust gapless excitations.

Theoretical predictions align with experimental observations.

Abstract

Topological insulators are found in materials that have elements with strong spin orbit interaction. However, electron Coulomb repulsion also potentially generates the topological insulators as well as Chern insulators by the mechanism of spontaneous symmetry breaking, which is called topological Mott insulators. The quantum criticality of the transition to the topological Mott insulators from zero-gap semiconductors follows unconventional universality distinct from the Landau-Ginzburg-Wilson scenario. On the pyrochlore lattice, the interplay of the electron correlation and the spin orbit interaction provides us in a rich phase diagram not only with simple topological insulators but also with Weyl semimetal and topologically distinct antiferromagnetic phases. Magnetic domain wall of the all-in-all-out type antiferromagnetic order offers a promising candidate of magnetically controlled transport, because, even when the Weyl points disappears, the domain wall maintains robust gapless excitations with Fermi surfaces around it embedded in the bulk insulator and bears uniform magnetization simultaneously. The ingap state is protected by a mechanism similar to the solitons in polyacetylene. Puzzling experimental results of pyrochlore iridates are favorably compared with the prediction of the domain wall theory.