Spectroscopic Visualization of a Robust Electronic Response of Semiconducting Nanowires to Deposition of Superconducting Islands

Abstract

Following significant progress in the visualization and characterization of Majorana end modes in hybrid systems of semiconducting nanowires and superconducting islands, much attention is devoted to the investigation of the electronic structure at the buried interface between the semiconductor and the superconductor. The properties of that interface and the structure of the electronic wavefunctions that occupy it determine the functionality and the topological nature of the superconducting state induced therein. Here we study this buried interface by performing spectroscopic mappings of superconducting aluminum islands epitaxially grown in-situ on indium arsenide nanowires. We find unexpected robustness of the hybrid system as the direct contact with the aluminum islands does not lead to any change in the chemical potential of the nanowires, nor does it induce a significant band bending in their vicinity. We attribute this to the presence of surface states bound to the facets of the nanowire. Such surface states, that are present also in bare nanowires prior to aluminum deposition, pin the Fermi-level thus rendering the nanowires resilient to surface perturbations. The aluminum islands further display Coulomb blockade gaps and peaks that signify the formation of a resistive tunneling barrier at the InAs-Al interface. At low energies we identify a potential energy barrier that further suppresses the transmittance through the interface. A corresponding barrier exists in bare semiconductors between surface states and the accumulation layer, induced to maintain charge neutrality. Our observations elucidate the delicate interplay between the resistive nature of the InAs-Al interface and the ability to proximitize superconductivity and tune the chemical potential in semiconductor-superconductor hybrid nanowires.

arXiv comment32 pages, 10 figures

References in corpus (21)

• Signatures of Majorana fermions in hybrid superconductor-semiconductor nanowire devices
• Majorana Fermions and a Topological Phase Transition in Semiconductor-Superconductor Heterostructures
• Helical liquids and Majorana bound states in quantum wires
• Evidence of Majorana fermions in an Al - InAs nanowire topological superconductor
• Realizing Majorana zero modes in superconductor-semiconductor heterostructures
• Scalable Designs for Quasiparticle-Poisoning-Protected Topological Quantum Computation with Majorana Zero Modes
• Epitaxy of Semiconductor-Superconductor nanowires
• Andreev bound states versus Majorana bound states in quantum dot-nanowire-superconductor hybrid structures: Trivial versus topological zero-bias conductance peaks
• Hard gap in epitaxial semiconductor-superconductor nanowires
• Effects of gate-induced electric fields on semiconductor Majorana nanowires
• Roadmap to Majorana surface codes
• Hybridization at superconductor-semiconductor interfaces
• Effective theory approach to the Schrodinger-Poisson problem in semiconductor Majorana devices
• Density of states and supercurrent in diffusive SNS junctions: role of nonideal interfaces and spin-flip scattering
• Detecting Majoranas in 1D wires by charge sensing
• Superconducting parity effect across the Anderson limit
• Universal Quenching of Superconductivity in Two-dimensional Nano-islands
• Effects of the electrostatic environment on superlattice Majorana nanowires
• Quantum confinement effects in Pb Nanocrystals grown on InAs
• Hot Electrons Regain Coherence in Semiconducting Nanowires
• Low-temperature scanning tunneling microscopy of ring-like surface electronic structures around Co islands on InAs(110) surfaces

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• Tunable proximity effects and topological superconductivity in ferromagnetic hybrid nanowires
• Improved effective equation for the Rashba spin-orbit coupling in semiconductor nanowires
• Coulomb Blockade Effects in a Topological Insulator Grown on a High-Tc Cuprate Superconductor
• Honing in on a topological zero-bias conductance peak
• Dynamical Coulomb Blockade as a Signature of the Sign-Reversing Cooper Pairing Potential
• Imaging asymmetric Coulomb blockade phenomena across metallic nanoislands