Magnetic-field regulation of nodal topological superconducting states in monolayer Ising superconductor NbSe${}_2$

The nodal topological superconducting (NTSC) state with Majorana flat bands (MFBs) is an exotic matter of state hosting Majorana fermions that obey non-Abelian statistics. Recently, monolayer Ising superconductor NbSe${}_2$ is shown to be an ideal platform for realizing an NTSC state. Through tight-binding calculations based on the Bogoliubov-de-Gennes Hamiltonian, it is demonstrated that the in-plane magnetic field B combined with superconducting pairing Δ${}_s$, Rashba spin-orbit coupling (SOC) V${}_r$, and chemical potential µ can regulate the topological properties of the NTSC state. First, B larger than Δ${}_s$ effectively induces an NTSC state with nodal points (NPs) located on the high-symmetry line of the Brillouin zone. The length of the resulting MFBs in the ribbon increases with B. Second, Rashba SOC greatly affects the number and locations of NPs by tilting bands near Fermi level (E${}_F$), leading to unidirectional Majorana edge states. Finally, when B > Δ${}_s$, µ affects the bulk band structure at E${}_F$, resulting in an NTSC state with 6, 12, 18, 24 NPs and 0, 2, 3, 4 MFBs. These results are important to clarifying the behavior of the NTSC state under a B and designing a quantum computing platform based on exotic Majorana fermions. (© 2023 Wiley‐VCH GmbH)