2010/01/31 by G. Rosenberg, Marcel Franz, M. Franz · 3 citations
Mathematics · Physics and Astronomy · #Advanced Condensed Matter Physics #Axion #Charge (physics) #Combinatorics #Coupling (piping) #Electric charge #Magnetic monopole #Magnetism #Mathematics #Particle physics #Physics #Quantum and electron transport phenomena #Quantum mechanics #Topological Materials and Phenomena #Topological insulator #Topology (electrical circuits) #cond-mat.mes-hall #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.82.035105
published as Phys.Rev.B82:035105,2010 · 7 pages, 2 figures. Version to appear in PRB; minor changes, discussion of several issues expanded
arxiv created 2010/05/21 · openalex publication_date 2010/07/07 · arxiv updated 2014/11/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
It has been noted a long time ago that a term of the form \ensuremathθ(e2/2\ensuremathπh)B\ensuremath⋅E may be added to the standard Maxwell Lagrangian without modifying the familiar laws of electricity and magnetism. \ensuremathθ is known to particle physicists as the ``axion'' field and whether or not it has a nonzero expectation value in vacuum remains a fundamental open question of the standard model. A key manifestation of the axion term is the Witten effect: a unit magnetic monopole placed inside a medium with \ensuremathθ\ensuremath≠0 is predicted to bind a (generally fractional) electric charge \ensuremath-e(\ensuremathθ/2\ensuremathπ+n) with n integer. Here we conduct a test of the Witten effect based on the recently established fact that the axion term with \ensuremathθ=\ensuremathπ emerges naturally in the description of the electromagnetic response of a class of crystalline solids called topological insulators---materials distinguished by strong spin-orbit coupling and nontrivial band structures. Using a simple physical model for a topological insulator we demonstrate the existence of a fractional charge bound to a monopole by an explicit numerical calculation. We also propose a scheme for generating an ``artificial'' magnetic monopole in a topological insulator film that may be used to facilitate an experimental test of Witten's prediction.