Hourglass Dirac chains enable intrinsic topological superconductivity in nonsymmorphic silicides

TL;DR

This paper discovers that nonsymmorphic symmetries in silicides like TaPtSi lead to intrinsic topological superconductivity, featuring hourglass Dirac chains, unconventional triplet pairing, and Majorana modes, opening new avenues for topological quantum materials.

Contribution

It demonstrates that nonsymmorphic symmetries can stabilize intrinsic topological superconductivity with hourglass Dirac chains and triplet pairing in silicides, supported by experimental and theoretical evidence.

Findings

TaPtSi is a new superconducting nonsymmorphic silicide.

Time reversal symmetry is broken below T_c in TaPtSi.

Majorana surface modes are supported by the identified pairing state.

Abstract

Nonsymmorphic crystalline symmetries provide a robust route to symmetry-protected electronic topology, yet their role in stabilizing intrinsic topological superconductivity remains largely unexplored. Here, we report \ch{TaPtSi} as a new member of the superconducting nonsymmorphic silicide family, characterized via AC transport, magnetization, heat capacity, and muon spin rotation/relaxation ($\mu$SR) measurements. Zero field $\mu$SR reveals spontaneous internal magnetic fields below $T_{\rm c}$, establishing time reversal symmetry breaking in \ch{TaPtSi}. First principles calculations on \ch{TaPtSi} and its isostructural nonsymmorphic superconducting analogues reveal the presence of symmetry-protected hourglass dispersions. The "necks" of these dispersions form Dirac nodal rings and chains that reside near or intersect the Fermi level. Guided by Ginzburg Landau symmetry analysis, we identify an internally antisymmetric non unitary triplet pairing state as the unique ground state consistent with the experimental phenomenology. Based on Bogoliubov de Gennes calculations, we further demonstrate that this state supports Majorana surface modes, establishing its intrinsically topological nature. These results reveal a systematic route by which nonsymmorphic symmetry drives the interplay between hourglass Dirac chain topology and unconventional triplet pairing, positioning equiatomic silicides as a unified materials platform for intrinsic topological superconductivity.