Electromagnetic response of topological superconductors

We resolve several puzzles related to the electromagnetic response of topological superconductors in 3+1 dimensions. In particular we show by an analytical calculation that the interface between a topological and normal superconductor does not exhibit any quantum Hall effect as long as time reversal invariance is preserved. We contrast this with the analogous case of a topological insulator to normal insulator interface. The difference is that in the topological insulator the electromagnetic vector potential couples to a vector current in a theory with a Dirac mass, while in the superconductor a pair of Weyl fermions is gapped by Majorana masses and the electromagnetic vector potential couples to its axial currents.

Automated summary

The study reveals that the interface between a topological superconductor and a normal superconductor does not exhibit quantum Hall effect, in contrast to the case of a topological insulator to normal insulator interface. This difference is attributed to the different theoretical models in the coupling of electromagnetic vector potential in the two systems.