Transport study of the wormhole effect in three-dimensional topological insulators

Inside a three-dimensional strong topological insulator, a tube with $h/2e$ magnetic flux carries a pair of protected one-dimensional linear fermionic modes. This phenomenon is known as the ``wormhole effect.'' In this work, we find that the wormhole effect, as a unique degree of freedom, introduces exotic transport phenomena and thus manipulates the transport properties of topological insulators. Our numerical results demonstrate that the transport properties of a double-wormhole system can be manipulated by the wormhole interference. Specifically, the conductance and local density of states both oscillate with the Fermi energy due to the interference between the wormholes. Furthermore, by studying the multiwormhole systems, we find that the number of wormholes can also modulate the differential conductance through a ${\mathbb{Z}}<sub>2</sub>$ mechanism. Finally, we propose two types of topological devices in real applications, the ``wormhole switch'' device and the ``traversable wormhole'' device, which can be finely tuned by controlling the wormhole degree of freedom.