Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 11: Electronic Structure of Surfaces: Spectroscopy, Surface States I

O 11.2: Talk

Monday, March 17, 2025, 15:15–15:30, H4

Excitation-Mediated Transport through Nano-scale Josephson Junctions in the Coulomb Blockade Regime — •Zhengyuan Liu, Sebastian Scherb, Werner M.J. van Weerdenburg, Daniel Wegner, Nadine Hauptmann, and Alexander A. Khajetoorians — IMM, Radboud University Nijmegen, the Netherlands

Josephson junctions (JJs) are essential for superconducting quantum computing and sensing technologies. It has been shown that superconductivity in elemental BCS superconductors, including those typically used for JJs [1], can persist down to the 2D limit. However, the effects of such quantum confinement on both the electronic structure of a JJ and its subsequent transport remains unclear, and fabricating conventional source-drain JJ devices at the nanometer scale is challenging. Here, we use low-temperature scanning tunneling microscopy and spectroscopy to study the electronic structure and transport of model nano-JJ stacks grown on Si(111) surface. We first characterize the quantum well states and superconducting gap of the underlying layer. Then, we explore how both the dielectric and overlying metallic layer affect the electronic and superconducting states. We study the tunneling transport in the Coulomb blockade limit for a number of JJ stacks, revealing that the conductance is dominated by an excitation mediated process. We also discuss the superconducting properties of these stacks, and the potential to detect superconductivity through their charge transport. [1] Werner M. J. van Weerdenburg et al. Sci. Adv. 9, eadf5500 (2023).

Keywords: Josephson junctions; Coulomb blockade; Quantum confinement; Excitations; Electron transport