Induced half-metallicity and gapless chiral topological superconductivity in the CrI3-Pb interface

We study a two-dimensional heterostructure comprised of a monolayer of the magnetic insulator chromium triiodide (CrI3) on a superconducting lead (Pb) substrate. Through first-principles computation and a tight-binding model, we demonstrate that charge transfer from the Pb substrate dopes the CrI3 into an effective half-metal, allowing for the onset of a gapless topological superconductivity phase via the proximity effect. This phase, in which there exists a superconducting gap only in part of the Fermi surface, is shown to occur generically in two-dimensional (2D) half-metal-superconductor heterostructures which lack twofold in-plane rotational symmetry. However, a sufficiently large proximity-induced pairing amplitude can bring such a system into a fully gapped topological superconducting (TSC) phase. As such, these results are expected to better define the optimal 2D component materials for future proposed TSC heterostructures.