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.
Highlights
Correlated systems are known for a whole range of spectacular phenomena such as, e.g., colossal magnetoresistance of manganese oxides [1], high-temperature superconductivity of cuprates [2] and iron arsenides [3], enormous volume expansions in elemental cerium [4] and plutonium [5], heavy electron-mass renormalizations in compounds containing f and, sometimes, d electrons [6], etc
The theme of strong correlations has come into play with the notion of topology in electronic band structures, whose robust quantum states are insensitive to perturbations and are currently attracting a great interest in materials such as topological insulators (TIs) [7] and Weyl semimetals (WSMs) [8]
Given the fact that the uranium sites arrange themselves on an inversion symmetric face-centered cubic sublattice with their odd-parity localized 5f electrons lying in close proximity to the Fermi level, it is interesting to speculate whether the possibility of inversion with the evenparity U 6d band is taking place
Summary
Correlated systems are known for a whole range of spectacular phenomena such as, e.g., colossal magnetoresistance of manganese oxides [1], high-temperature superconductivity of cuprates [2] and iron arsenides [3], enormous volume expansions in elemental cerium [4] and plutonium [5], heavy electron-mass renormalizations in compounds containing f and, sometimes, d electrons [6], etc. Fermions in particle physics and the associated Fermi-arc surface states [9], the field has been enriched by the discoveries of topological Kondo insulator [10] behavior in SmB6 [11] and filled skutterudites [12] and plutonium and americium TIs based on rocksalt structure [13], as well as heavy-fermion Weyl-Kondo semimetals [14] These systems, representing a merge between paradigms of correlations and topology, could serve as the basis for studying yet-unknown electronic phases, transitions, and functionalities and may lead to interesting applications in the future. Signatures of localized electronic states originating from atomic multiplet transitions, known as Hubbard bands, as well as strongly renormalized quasiparticle bands in the vicinity of the Fermi level, often both appear in materials with strong correlations Such competition between localization and delocalization is at the heart of the Mott transition problem [15], which has been well understood through the development of the dynamical meanfield theory (DMFT) [16].
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