MARCH 27, 2026 -- In modern physics, two ideas have transformed our understanding of matter: topology and emergence. Topology describes global, robust properties of materials that remain unchanged under continuous deformations, giving rise to protected electronic states that are immune to disorder. Emergence, on the other hand, captures how complex collective behavior - such as magnetism or strong correlations - arises from simple microscopic ingredients. When these two concepts meet, they open the door to entirely new forms of quantum matter.

An international research team has now identified a family of materials, RAsS (R = Y, La, Sm), that exemplifies this powerful combination. These compounds crystallize in a newly refined structure and host robust topological surface states protected by crystalline symmetries, making them promising platforms for exploring symmetry-protected quantum phenomena. What makes this discovery particularly exciting is the behavior of the Sm-based compound. Experimental signatures point to strong mass enhancement, a hallmark of electronic correlations and heavy-fermion physics. To understand this interplay between topology and correlations, the team combined first-principles electronic structure calculations with a slave-boson theoretical framework, a powerful method to capture many-body effects. Their results demonstrate that, remarkably, the topological surface states survive even in the presence of strong correlations.

This work establishes RAsS materials as a new class of systems where topology and heavy-fermion physics coexist, adding to a very small and highly sought-after family of materials with thess properties. This not only deepens our understanding of quantum matter but also paves the way toward future technologies based on robust, correlation-driven electronic states.

This work was published earlier this month in the Journal of the American Chemical Society.