Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 15: Topology: Majorana Physics

TT 15.5: Vortrag

Montag, 9. März 2026, 16:00–16:15, HSZ/0105

Characterization of side-contacted topological-insulator-nanowire junctions — •Ella Nikodem, Jakob Schluck, and Yoichi Ando — II. Physikalisches Institut, Universität zu Köln

Superconducting hybrid devices based on topological insulator (TI) nanowires are a promising platform for realizing topological superconductivity and hosting Majorana zero modes (MZMs). We report our recent efforts to realize high-quality Josephson junctions based on etched BiSbTeSe2 nanowires laterally sandwiched with superconducting Nb. This device architecture enables full surface proximitization and forms an intrinsic columnar nano-SQUID, in which the top and bottom surfaces act as parallel SNS junctions. Upon threading a magnetic flux, we observe two key phenomena: (1) robust SQUID-like oscillations of the critical current with the periodicity of the superconducting flux quantum, confirming surface-dominated supercurrent [1]; and (2) a large gate- and field-tunable Josephson diode effect [2]. Conceptually, this device geometry allows for individual tuning of the phase difference of the top and bottom junctions, enabling the creation of a discrete vortex at the end of the nanowire that hosts a MZM [3]. This is substantiated by theoretical considerations based on both a phenomenological approach and full 3D tight-binding simulations. Preliminary tunnel spectroscopy results further pave the way towards detecting Majorana bound states in this platform.
[1] E. Nikodem et al., https://arxiv.org/abs/2412.07993
[2] E. Nikodem et al., Sci. Adv. 11 (2025) eadw4898
[3] L. Fu and C. Kane, Phys. Rev. Lett. 100 (2008) 096407

Keywords: Topological superconductivity; Nanotransport; Majorana