Emergent topological semimetal from quantum criticality

The electronic topology of a material is generally described by its Bloch states and the associated band structure, and can be altered by electron–electron interactions. In metallic systems, the interactions are usually treated through the concept of quasiparticles. Here we investigate what happens if no well-defined quasiparticles are present and show that a topological semimetal phase can emerge from the material’s quantum critical state. Using the non-centrosymmetric heavy-fermion compound CeRu₄Sn₆, which is intrinsically quantum critical, we show that the topological phase exhibits a dome structure as a function of the magnetic field and pressure. To understand these results, we study a Weyl–Kondo semimetal model at a Kondo destruction quantum critical point. Indeed, it exhibits features in the spectral function that can define topological crossings beyond the quasiparticle picture. Our results outline the importance of the interplay of quantum critical fluctuations and symmetry to search for other emergent topological phases.