Superconductivity in Hourglass Dirac Chain Metals (Ti, Hf)IrGe

Abstract Realizing superconductivity in stoichiometric topological materials is a major focus in condensed matter physics, as it paves the way to achieve topological superconductivity. Here, it is reported that the discovery of ternary germanide superconductors, M IrGe ( M = Ti, Hf), predicted to exhibit non‐symmorphic symmetry‐protected hourglass Dirac chains, can be prime candidates for topological superconductivity. Using comprehensive thermodynamic and muon‐spin rotation/relaxation (µSR) measurements, these materials are established as conventional bulk type‐II superconductors with transition temperatures of 2.24(5) K for TiIrGe and 5.64(4) K for HfIrGe, featuring a full gap and preserved time‐reversal symmetry. First‐principles calculations reveal striking topological features in M IrGe, including hourglass‐shaped bulk dispersions and a Dirac chain ‐ a ring of fourfold ‐ degenerate Dirac points protected by nonsymmorphic symmetry. Each Dirac point corresponds to the neck of the hourglass dispersion, while the Dirac chain gives rise to drumhead ‐ like surface states near the Fermi level. Additionally, nontrivial topology leads to isolated Dirac surface states with helical spin textures that disperse across the Fermi level, forming an ideal platform for proximity‐induced topological superconductivity. The coexistence of conventional bulk superconductivity, symmetry‐protected hourglass topology, and helical spin‐textured surface states suggests M IrGe as a rare platform to achieve topological superconductivity, opening new avenues for next‐generation quantum technologies.