Regensburg 2022 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 18: Topological Insulators

TT 18.9: Talk

Wednesday, September 7, 2022, 11:30–11:45, H23

Coulomb-blockade spectroscopy in topological insulator-superconductor hybrid devices — •Benedikt Frohn, Tobias W. Schmitt, Wilhelm Wittl, Dennis Heffels, Michael Schleenvoigt, Abdur R. Jalil, Detlev Grützmacher, and Peter Schüffelgen — Peter Grünberg Institut, Forschungszentrum Jülich & JARA Jülich-Aachen Research Alliance, D-52425 Jülich, Germany

In the search for fault tolerant quantum computing, Majorana zero modes resemble a promising platform [1]. We investigate an island of a topological insulator (TI) nanoribbon, (Bi,Sb)₂Te₃, proximitized with a superconductor (S) for signatures of these states using Coulomb-blockade spectroscopy. One possible signature would be a change in charge periodicity once the island is tuned into the topological regime. We successfully created tunneling barriers made from Al₂O₃ and obtained the characteristic Coulomb diamond structure. Nb provides excellent interface transparency towards TI and was capped insitu, yet we found no change in charge periodicity. Al, however, is known to show these signatures in comparable experiments. Since Al diffuses heavily into the TI when put directly into contact, we fabricated Josephson junctions (JJs) with different thin interlayers between (Bi,Sb)₂Te₃ and Al to characterize the influence of these diffusion barriers on the transport properties of the JJs. We find four possible interlayers that allow for engineering a transparent S-TI interface. These results will enable us to perform Coulomb-blockade experiments with Al as a S.

[1] A.Y. Kitaev, Ann. Phys. 303, 2 (2003)