Correlation Driven Topological Insulator-to-Weyl Semimetal Transition in Actinide System UNiSn

TL;DR

This paper predicts a topological insulator to Weyl semimetal transition in the actinide compound UNiSn driven by strong electronic correlations, revealing a new type of phase transition in strongly correlated topological matter.

Contribution

It introduces a combined density functional and dynamical self-energy approach to identify topological phases in UNiSn, linking the insulator-metal transition to a topological phase change.

Findings

UNiSn exhibits TI and WSM phases in different magnetic states.

The insulator-metal transition is a TI-to-WSM transition.

Multiple energy gaps with topological properties are identified.

Abstract

Although strong electronic correlations are known to be responsible for some highly unusual behaviors of solids such as, metal--insulator transitions, magnetism and even high--temperature superconductivity, their interplay with recently discovered topological states of matter awaits full exploration. Here we use a modern electronic structure method combining density functional theory of band electrons with dynamical self-energies of strongly correlated states to predict that two well-known phases of actinide compound UNiSn, a paramagnetic semiconducting and antiferromagnetic metallic, correspond to Topological Insulator (TI) and Weyl semimetal (WSM) phases of topological quantum matter. Thus, the famous unconventional insulator-metal transition observed in UNiSn is also a TI-to-WSM transition. Driven by a strong hybridization between U f-electron multiplet transitions and band electrons, multiple energy gaps open up in the single-particle spectrum whose topological physics is revealed using the calculation of Z2 invariants in the strongly correlated regime. A simplified physical picture of these phenomena is provided based on a periodic Anderson model of strong correlations and multiple band inversions that occur in this fascinating compound. Studying the topology of interacting electrons reveals interesting opportunities for finding new exotic phase transitions in strongly correlated systems.