Interplay of Tilt and Axion Fields in Topological Superconductors: Anisotropy in the Meissner Effect

Abstract: The surface states of topological superconductors significantly influence electromagnetic fields within these materials. The interaction between gapless boundary states and electromagnetic fields induces a Berry phase, coupling electric and magnetic fields and introducing the axion term into the effective Lagrangian . In this paper, we utilize a model of a topological superconductor, represented as a Weyl superconductor-topological insulator-Weyl superconductor structure with a {\pi} phase difference between superconductors. By incorporating tilting of Weyl cones, we study the Meissner effect, demonstrating that the interplay between tilt and the axion field enhances surface state contributions. Furthermore, we show that an anisotropy in the Meissner effect arises from the anisotropic nature of the tilt vector. This anisotropy manifests as directional dependence in the magnetic response of the material. We derive a universal equation for magnetic penetration in topological superconductors and explore the impact of tilt on the planar Hall current at the surface.