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TT: Fachverband Tiefe Temperaturen

TT 89: Focus Session: Evolution of Topological Materials into Superconducting Nanodevices (joint session HL/TT)

TT 89.4: Invited Talk

Friday, March 22, 2024, 11:15–11:45, EW 202

Tunable Josephson coupling in HgTe nanodevices — •Martin P. Stehno — Physikalisches Institut EP3 und Institut für Topologische Isolatoren, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany

Mercury telluride offers access to a variety of topological phases in a single material system. This opens up opportunities for disentangling the complex interplay of band structure effects, interface preparation, and phase dynamics that characterize the Josephson effect in topological insulator nanodevices. We study a new generation of gate-tunable Josephson junctions with weak links fabricated from 2D and 3D topological insulator HgTe. These devices feature ballistic transport over a wide range of carrier densities and allow us to map out the Josephson coupling of topological states and bulk modes using a combination of quantum transport methods, supercurrent interference, and microwave spectroscopy. By adding a gated constriction into a 2D topological insulator weak link, we create a quantum point contact (QPC) that allows us to study the ac Josephson effect as a function of the number of open channels. As we deplete the constriction further, we explore proximity-induced superconductivity in the quantum spin Hall edge channels and in the regime of the recently discovered 0.5-anomaly in HgTe QPC devices.

Keywords: topological insulator; Josephson effect; quantum point contact; supercurrent; field-effect