Josephson Currents Induced by the Witten Effect

Condensed Matter Seminars

Speaker: Jeroen van den Brink, Institute for Theoretical Solid State Physics, IFW Dresden
Date & Time: November 24, 2016 2:00 - 3:00
Location: Hennings 318
Local Contact: Mona Berciu
Intended Audience: Graduate

We reveal the existence of a new type of topological Josephson effect involving type II superconductors and three-dimensional topological insulators as tunnel junctions. We predict that vortex lines induce a variant of the Witten effect that is the consequence of the axion electromagnetic response of the topological insulator: at the interface of the junction each flux quantum attains a fractional electrical charge of e/4. As a consequence, if an external magnetic field is applied perpendicular to the junction, the Witten effect induces an ac Josephson effect in the absence of any external voltage. We derive a number of further experimental consequences and propose potential setups where these quantized, flux induced Witten effects may be observed [1].

[1] Physical Review Letters 117, 167002 (2016)