Prediction of topological superconductivity from type-IV, -III, -II, and -I′ nodal points induced by Rashba spin-orbit coupling

Topological superconductivity (TSC) has received great theoretical and experimental attention recently. Type-I Rashba nodal point (RNP) with isotropic band dispersions and point Fermi surface (FS) induced by the Rashba spin-orbit coupling (SOC) provides a promising route to the artificial TSC, because the inherent interspin coupling (ISC) shares identical form as the p-wave pairing (k(x)sigma(y)-k(y)sigma(x)) exactly. Here we discuss the potential TSC of other types of RNPs with different ISC forms. By constructing a generic tight-binding model with Rashba SOC, we demonstrate type-IV, -III, -II, and -I' RNPs can be achieved on two-dimensional (2D) Bravais lattices, whose FS consists of only a hole (electron) pocket, two contacted hole (electron) pockets, contacted hole and electron pockets, and point of tangency, respectively. With the coorpration of s-wave pairing and Zeeman gaps, these new types of RNP will evoke TSC phases with chiral Majorana edge modes (MEMs), where the Chern number will be larger than 1 for multiple symmetry-equivalent RNPs. The Chern number can be further composited when the energies of unequivalent RNPs are equal, leading to edge-dependent MEMs. Moreover, by using first-principles calculations, we demonstrate the BiSb monolayer is an ideal platform for realizing TSC with Chern number 6 from type-II, -I, or -IV RNP. This work enriches the types of nodal point induced by Rashba SOC and offers a generic guidance on realizing multiple and edge-dependent MEMs from the abundantly synthesized 2D surface metal layers.

Automated summary

Topological superconductivity (TSC) has received significant attention recently, with researchers exploring the potential of different types of Rashba nodal points (RNPs) to induce TSC. By constructing tight-binding models with Rashba spin-orbit coupling (SOC), researchers have demonstrated the possibility of achieving various types of RNPs on 2D Bravais lattices, leading to TSC phases with chiral Majorana edge modes (MEMs). Furthermore, first-principles calculations have shown that the BiSb monolayer could serve as an ideal platform for realizing TSC with high Chern numbers.