Dissipationless conductance in a topological coaxial cable

We present a dynamical mechanism leading to dissipationless conductance, whose quantized value is controllable, in a (3+1)-dimensional electronic system. The mechanism is exemplified by a theory of Weyl fermions coupled to a Higgs field--also known as an axion insulator. We show that the insertion of an axial gauge flux can induce vortex lines in the Higgs field, similarly to the development of vortices in a superconductor upon the insertion of magnetic flux. We further show that the necessary axial gauge flux can be generated using Rashba spin-orbit coupling or a magnetic field. Vortex lines in the Higgs field are known to bind chiral fermionic modes, each of which serves as a one-way channel for electric charge with conductance $e^2/h$. Combining these elements, we present a physical picture, the "topological coaxial cable," illustrating how the value of the quantized conductance could be controlled in such an axion insulator.