Strong Correlation Effects on Topological Quantum Phase Transitions in Three Dimensions

TL;DR

This study explores how short-range electron interactions influence topological phase transitions in 3D insulators, revealing a critical interaction strength that changes the nature of the transition and the emergence of a Mott-like topological state.

Contribution

It provides new insights into the effects of Coulomb and Hund's interactions on topological phase transitions using dynamical mean-field theory.

Findings

Identification of a critical U value separating continuous and first-order transitions.

Discovery of a Mott insulator stabilized at large U with topological properties.

Observation of a Mott-like topological state near the Mott transition.

Abstract

We investigate the role of short-ranged electron-electron interactions in a paradigmatic model of three dimensional topological insulators, using dynamical mean-field theory and focusing on non magnetically ordered solutions. The non-interacting band-structure is controlled by a mass term M, whose value discriminates between three different insulating phases, a trivial band insulator and two distinct topologically non-trivial phases. We characterize the evolution of the transitions between the different phases as a function of the local Coulomb repulsion U and find a remarkable dependence of the U -M phase diagram on the value of the local Hund's exchange coupling J. However, regardless the value of J, following the evolution of the topological transition line between a trivial band insulator and a topological insulator, we find a critical value of U separating a continuous transition from a first-order one. When the Hund's coupling is significant, a Mott insulator is stabilized at large U . In proximity of the Mott transition we observe the emergence of an anomalous "Mott-like" strong topological insulating state.