(De)confinement of supercurrent in Z_2 Topological Insulators

TL;DR

This paper investigates how supercurrents behave in Z_2 topological insulators, revealing a transition between confined and deconfined states driven by spin-orbit interactions, with implications for dissipationless current flow.

Contribution

It demonstrates the conditions under which supercurrents are confined or deconfined in Z_2 topological insulators, highlighting the role of spin symmetry breaking.

Findings

Supercurrent flows in Z_2 topological insulators with combined gauge symmetries.

Breaking U_z(1) symmetry leads to confined but not dissipative currents.

Rashba spin-orbit interaction induces a transition between confining and deconfining states.

Abstract

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).