Spectroscopic Visualization of Hard Quasi-1D Superconductivity Induced in Nanowires Deposited on a Quasi-2D Indium film

TL;DR

This study introduces a novel hybrid platform combining InAsSb nanowires on a superconducting Indium film, enabling detailed spectroscopic analysis of quasi-1D superconductivity and its topological properties.

Contribution

The paper presents a new architecture for inducing superconductivity in nanowires, preserving their top facet for spectroscopic studies and demonstrating high Cooper-pair transparency.

Findings

High Cooper-pair transparency (~90%) at the interface

Anisotropic magnetic response indicating quasi-2D and quasi-1D superconductivity

Platform suitable for studying topological superconductivity

Abstract

Following significant progress in the visualization and characterization of hybrid superconducting-semiconducting systems, greatly propelled by reports of Majorana zero modes in nanowire devices, considerable attention has been devoted to investigating the electronic structure at the buried superconducting-semiconducting interface and the nature of the induced superconducting correlations. The properties of that interface and the structure of the electronic wave functions that occupy it determine the functionality and the topological nature of the induced superconducting state. Here, we introduce a novel hybrid platform for proximity-inducing superconductivity in InAs$_{0.6}$Sb$_{0.4}$ nanowires, leveraging a unique architecture and material combination. By dispersing these nanowires over a superconducting Indium film we exploit Indium's high critical temperature of 3.7~K and the anticipated high spin-orbit and Zeeman couplings of InAs$_{0.6}$Sb$_{0.4}$. This design preserves the pristine top facet of the nanowires, making it highly compatible with scanning tunneling spectroscopy. Using this architecture we demonstrate that the mechanical contact supports Cooper-pair transparency as high as 90\%, comparable with epitaxial interfaces. The anisotropic angular response to an applied magnetic field shows the quasi-two-dimensional nature of the parent superconductivity in the Indium film and the quasi-one-dimensional nature of the induced superconductivity in the nanowires. Our platform offers robust and advantageous foundations for studying the emergence of topological superconductivity and the interplay of superconductivity and magnetism using atomic-scale spectroscopic tools.