Emergent heavy-fermion physics in a new family of topological insulators RAsS (R = Y, La, and Sm)

TL;DR

This paper discovers a new family of topological insulators with strong electron correlations, revealing hourglass fermions and heavy-fermion behavior, and models their surface states under Kondo physics.

Contribution

It identifies a new RAsS series with topological and heavy-fermion features, and develops a minimal model to describe their correlated surface states.

Findings

YAsS and SmAsS host hourglass fermions protected by glide symmetry.

SmAsS exhibits strong effective-mass enhancement, linking it to known heavy-fermion materials.

Surface states are predicted to persist under Kondo correlations, shifted in energy.

Abstract

Realizing topological phases in strongly correlated materials has become a major impetus in condensed matter physics. Although many compounds are now classified as topological insulators, $f$-electron systems (with their strong electron correlations) provide an especially fertile platform for emergent heavy-fermion phenomena driven by the interplay of topology and many-body effects. In this study, we examine the crystalline topology of a new RAsS series (R = Y, La, Sm), revealing a structural variant from previous reports. We demonstrate that YAsS and SmAsS host hourglass fermions protected by glide symmetry. SmAsS notably exhibits a strong effective-mass enhancement, placing it alongside SmB${}_6$ and YbB${}_{12}$ as a material that couples topological surface states with emergent Kondo physics, yet distinguished by its crystalline symmetry constraints and $f$-$p$ orbital hybridization. To capture these features, we construct a minimal model incorporating $f$-electron degrees of freedom, which reproduces the observed topological properties and predicts that the surface states survive in the correlated regime, albeit shifted in energy. Our work thus introduces a new family of correlated topological materials and forecasts the robustness of their surface states under Kondo correlations.