Inducing Z2 topology in twisted nodal superconductors

This is the authors' abstract. We don't add key points for this paper.

Twisted nodal superconductors have been shown to exhibit chiral topological superconductivity under broken time-reversal symmetry. Here we show how a time-reversal preserving topological superconductivity can be induced in nodal triplet superconductor multilayers. For a bilayer system, the application of a Josephson spin current in triplet superconductors induces a nonzero spin Chern number per node in momentum space. However, we show that stabilizing a nontrivial global Z₂ invariant requires an odd number of layers. As a specific example, we consider trilayers with three forms of twist: chiral, alternating, and single-layer. For chiral and single-layer case, we find that a gap opening in the dispersion leads to a nontrivial Z₂ topological invariant. For single-layer twists, we show how this invariant is nontrivial when extended to an arbitrary odd number of layers.