Fig. 1
Sketch of the bilayer system and phase diagram. a Illustration of the superconductor/topological insulator/superconductor (SC/TI/SC) heterostructure under an in-plane magnetic field Bx (big green arrow) possessing Majorana zero mode (MZM) chain (marked by the green spheres) at the boundary. b Illustration of the two Fermi surfaces with opposite spin textures (green arrows) for bilayer TI thin films with m0 = m1 = 0 in Eq. (2) under an in-plane magnetic field Bx. c Phase diagram of superconducting TI film in the absence of magnetic field, as a function of intra-layer interaction U and inter-layer interaction V. It consists of one metallic phase and three superconducting phases: the intra-layer A1g pairing \(\hat c_{t \uparrow }\hat c_{t \downarrow } + \hat c_{b \uparrow }\hat c_{b \downarrow }\), the inter-layer A1u pairing \(\hat c_{t \uparrow }\hat c_{b \downarrow } - \hat c_{b \uparrow }\hat c_{t \downarrow }\), and the intra-layer A2u pairing \(\hat c_{t \uparrow }\hat c_{t \downarrow } - \hat c_{b \uparrow }\hat c_{b \downarrow }\)
