We investigate the spontaneous decay of an atom in a cavity constructed by topological insulators. The method of Green's function in stratified cavities has been used and expressions of atomic decay rates in two directions parallel and perpendicular to cavity mirrors are derived. It is shown that when an atom is embedded closely to a topological insulator with a strong axion field, the spontaneous decay of the dipole parallel to the surface will be suppressed due to the high anisotropy of the vacuum. The appearance of indirect quantum interference of two orthogonal dipoles representing the dif...
