Spectroscopic visualization of hard quasi-one-dimensional superconductivity induced in nanowires deposited on a quasi-two-dimensional indium film

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 hybrid platform for proximity-inducing superconductivity in InAs0.6Sb0.4 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 InAs0.6Sb0.4. 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.