Josephson Currents Induced by the Witten Effect

Speaker: 
Jeroen van den Brink, Institute for Theoretical Solid State Physics, IFW Dresden, Germany
Event Date and Time: 
Thu, 2016-11-24 14:00 - 15:00
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) 

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