Topological superconductivity in superconducting chiral topological semimetals with parallel spin-momentum locking

TL;DR

This paper investigates how chiral topological semimetals with specific spin textures can host various unconventional and topological superconducting phases, including Majorana states, through theoretical modeling.

Contribution

It reveals the emergence of topological superconducting phases in chiral Weyl semimetals with parallel spin-momentum locking, introducing new possibilities for intrinsic topological superconductivity.

Findings

Identification of a first-order time-reversal invariant topological superconductor.

Prediction of a superconductor with two Majorana cones on the Fermi surface.

Proposal of a second-order topological superconductor with chiral Majorana states.

Abstract

In contrast to conventional Weyl semimetals in achiral crystals, chiral topological semimetals in chiral crystals exhibit Weyl nodes at time-reversal-invariant momenta. A Fermi surface spin texture with parallel spin-momentum locking in these material has been observed by a recent experiment [Nat. Comm. 15,3720(2024)]. We find that the Weyl nodes location and the Fermi surface spin texture lead to gapped zero-momenta intranode superconductivity (SC), which is absent in achiral Weyl semimetals. Through self-consistent mean-field calculations, we find that a cubic lattice system in general favors a mixture of spin-singlet $s_\pm$ and $d+id$-wave pairings. In the presence of only the $s_\pm$-wave pairing, we identify a first-order time-reversal invariant topological SC phase. Notably, an SC phase with two Majorana cones for opened Fermi surfaces is energetically favorable. In addition, a second-order topological superconductor with chiral Majorana states can be realized in the presence of a mixture of $s\pm$- and $d+id$-wave pairing. We show that chiral topological semimetals in cubic lattice are fascinating platforms for exploring intrinsic unconventional superconductivity and topological superconductivity.