(De)confinement of supercurrent in Z₂ Topological Insulators

It is shown that the electric supercurrent flows in a Z_2 topological insulator with U_em(1) X U_z(1) (electromagnetic and spin) gauge symmetries. When U_z(1) is broken, a dissipationless electric current is still possible to flow locally but net charge transfer is absent, i.e., current is confined. In the Kane-Mele model for graphene, this confining-deconfining (superconducting) transition is driven by the Rashba spin-orbit interaction, which breaks U_z(1).