Wormhole Effect in a Strong Topological Insulator

TL;DR

This paper demonstrates that inserting a magnetic flux tube into a strong topological insulator creates protected one-dimensional fermionic modes, revealing a unique bulk topological effect with potential experimental implications.

Contribution

It introduces the 'wormhole' effect, showing that magnetic flux in a strong topological insulator induces protected gapless modes, confirmed through qualitative analysis and numerical modeling.

Findings

Magnetic flux induces gapless fermionic modes in topological insulators.

The effect is confirmed via numerical calculations in a lattice model.

Potential for experimental observation in nanostructures.

Abstract

An infinitely thin solenoid carrying magnetic flux Phi (a `Dirac string') inserted into an ordinary band insulator has no significant effect on the spectrum of electrons. In a strong topological insulator, remarkably, such a solenoid carries protected gapless one-dimensional fermionic modes when Phi=hc/2e. These modes are spin-filtered and represent a distinct bulk manifestation of the topologically non-trivial insulator. We establish this `wormhole' effect by both general qualitative considerations and by numerical calculations within a minimal lattice model. We also discuss the possibility of experimental observation of a closely related effect in artificially engineered nanostructures.