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Transport in Superconductor-Topological Insulator-Superconductor 2D Arrays - Vincent Humbert

University of Illinois at Urbana-Champaign

LPS – amphi Moyen

Once coupled to s-wave superconducting material, three-dimensional topological insulators (TIs) – providing spin momentum locking of the electrons and spin polarized current at the surface – are expected to show novel properties and unconventional superconductivity. To probe the interplay between TI surface properties and superconductivity, we fabricated 2D superconducting island arrays on exfoliated flakes of the 3D TI Bi2Se3. Such two-dimensional junction arrays have been shown to undergo Kosterlitz-Thouless transitions toward a superconducting state.

During this seminar, I will present transport and Fraunhofer spectroscopy measurements carried out on our devices. These show unusual, asymmetric behavior. In particular, our measurements provide evidence of charged vortices on the topological surface. These are expected in TIs due to a variant of the Witten effect. Finally, I will expose follow up experiments we carried out confirming this picture and allowing to perform analogies between measurements performed in other systems.

This work was supported by the DOE Basic Energy Sciences under DE-SC0012649 and NSF DMR 17-10437


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