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TT: Fachverband Tiefe Temperaturen

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

TT 89.1: Hauptvortrag

Freitag, 22. März 2024, 09:30–10:00, EW 202

Tunneling spectroscopy of a phase-tunable topological insulator Josephson junction — •Jakob Schluck¹, Ella N. Nikodem¹, Anton Montag², Alexander Ziesen², Mahasweta Bagchi¹, Zhiwei Wang¹, Fabian Hassler², and Yoichi Ando¹ — ¹Institute of Physics II, University of Cologne — ²JARA-Institute for Quantum Information, RWTH Aachen University

Topological superconductivity is predicted to be realized in a topological insulator proximitized by an s-wave superconductor [1]. In such a system, vortices host Majorana zero modes - quasiparticle excitations obeying non-Abelian exchange statistics that could have important applications as topological qubits.

Here we present our experimental findings concerning the bound state spectrum of topological insulator Josephson junctions. We locally probe the density of states through tunnel contacts made on top of the junction, while tuning the phase difference across it by applying an external magnetic field.

We find a periodic filling of the induced gap, with states reaching zero energy for a local phase difference of π. Taking the phase gradient along the junction into account, we interpret those as signatures of Majorana zero modes bound to the π-phase boundary [2]. We will discuss their stability with respect to the chemical potential and possible trivial origins.

[1] Liang Fu and C. L. Kane, Phys. Rev. Lett. 100, 096407 (2008) [2] A. C. Potter and L. Fu, Phys. Rev. B 88, 121109 (2013).

Keywords: Topological insulators; Nanodevices; Majorana zero modes