Realizing topological superconductivity in stoichiometric materials is a key challenge in condensed matter physics. Here, we report the discovery of ternary germanide superconductors, MIrGe (M = Ti, Hf), as prime candidates for topological superconductivity, predicted to exhibit nonsymmorphic symmetry-protected hourglass Dirac chains. Using comprehensive thermodynamic and muon-spin rotation/relaxation (μSR) measurements, we establish these materials 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 MIrGe, 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 Z2 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 establishes MIrGe as a rare and robust platform to realize topological superconductivity, opening new avenues for next-generation quantum technologies.
@article{arxiv.2502.07475,
title = {Topological superconductivity in hourglass Dirac chain metals (Ti, Hf)IrGe},
author = {Pavan Kumar Meena and Dibyendu Samanta and Sonika Jangid and Roshan Kumar Kushwaha and Rhea Stewart and Adrian D. Hillier and Sudeep Kumar Ghosh and Ravi Prakash Singh},
journal= {arXiv preprint arXiv:2502.07475},
year = {2025}
}