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TT: Fachverband Tiefe Temperaturen

TT 15: Focus Session: Evolution of Topological Materials into Superconducting Nanodevices (joint session HL/TT)

TT 15.3: Vortrag

Montag, 18. März 2024, 15:30–15:45, EW 202

Andreev spectrum of Josephson junctions with topological insulator nanostructures — •Dennis Heffels, Peter Schüffelgen, Kristof Moors, and Detlev Grützmacher — Peter Grünberg Institute 9, Forschungszentrum Jülich, 52425 Jülich, Germany

Josephson junctions and the presence of Andreev bound states play an important role in quantum information and quantum materials research, forming an integral part of SQUIDs and superconducting qubits, for example. The bound states within a Josephson junction have a phase-dependent spectrum known as the Andreev spectrum. The investigation of this spectrum with phase-sensitive measurements can be used to characterize exotic types of superconductivity, such as topological superconductors with Majorana bound states. Here we present a method to efficiently calculate numerically detailed Andreev spectra, based on a scattering matrix method and (3D) tight binding, for different junction geometries, chemical potential and disorder profiles, etc. We apply this method to proximitized topological insulator (TI) nanostructure-based junctions in which Majorana bound states are expected upon application of an external magnetic field. In this setup, the spin-momentum-locked topological surface states give rise to highly unconventional Andreev spectra and corresponding current-phase relationships, both in the topologically trivial and nontrivial superconducting regimes.

Keywords: Andreev spectrum; Andreev bound state; Josephson junction; Topological insulator; Majorana bound states