Topological Insulator-to-Weyl Semimetal Transition in Strongly Correlated Actinide System UNiSn

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 a full exploration. Here, we use a modern electronic structure method, combining the 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 exotic phase transitions in strongly correlated systems.