Emergent Heavy-Fermion Physics in a Family of Topological Insulators R AsS ( R = Y, La, and Sm)

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 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 SmB₆ and YbB₁₂ as a material that exemplifies how the Kondo effects pin the correlated f-electron states near the Fermi energy and, consequently, renormalize the energy and mass scales of topological surface states without destroying their crystalline protection. This tunability establishes SmAsS as a bridge between weakly correlated topological materials and Kondo insulators. 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.