Scientists report a theoretical route to topological superconductivity in recently discovered high-temperature bilayer nickelate films. Using calculations guided by first-principles electronic structure, the authors show that thin films placed on a substrate can develop a time-reversal-invariant topological superconducting state. That state is protected by a diagonal mirror symmetry and would host special low-energy boundary states called Majorana Kramers pairs.

The team built a simple two-orbital model that captures the low-energy bands of a LaNiO-based bilayer grown on a SrLaAlO substrate. Important ingredients in the model are a layer-asymmetric potential and a layer-staggered Rashba spin-orbit coupling. Spin-orbit coupling is an interaction that ties an electron’s spin to its motion; Rashba spin-orbit coupling appears when inversion symmetry is broken and, in this case, it acts with opposite sign on the two layers. With these substrate-induced effects and a dominant interlayer pairing (pairing that links electrons in the two layers), the model enters a topological phase over a broad parameter range.

At a physical level the topology comes from a reversal of the superconducting pairing sign on one of the spin-split bonding Fermi surfaces. In other words, electrons on different parts of the Fermi surface have pairings with opposite signs, and the spin splitting produced by the layer-staggered spin-orbit coupling makes this sign change topologically nontrivial. The authors characterize the phase by a nonzero mirror winding number along the diagonal direction, predict a Majorana Kramers pair localized on the [11] edge, and find bulk gap nodes slightly off the diagonal that carry chiral charge and produce zero‑energy flat bands on a different edge.

This proposal matters because it links the unusual pairing believed to be present in bilayer nickelates to topology. If realized, the Majorana boundary modes would provide a phase-sensitive probe of the pairing symmetry and a platform for studying Majorana physics at relatively high temperatures compared with other candidate materials. The mechanism also suggests practical tuning knobs: the substrate, strain, and charge transfer can change the layer potential and spin-orbit strength and thus drive or remove the topological phase.