Proximity Effect Transfer from NbTi into a Semiconductor Heterostructure via Epitaxial Aluminum

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Superconducting proximity effect enables the transfer of superconducting properties to non-superconducting materials.
• Indium Arsenide (InAs) is a promising material for topological quantum computing due to its strong spin-orbit coupling.
• Niobium Titanium (NbTi) is a high-critical-field superconductor suitable for robust superconducting properties.

Discussion:

• Demonstrated successful transfer of NbTi superconductivity into an InAs heterostructure using an epitaxial Aluminum (Al) interface layer.
• Utilized Josephson junctions and quantum point contacts to probe interface transparency and the proximity effect.
• Observed near-unity interface transparency and a significant induced superconducting gap (Δ* = 0.50 meV) in the InAs.

Key Insights:

• Multiple Andreev reflections in Josephson junctions confirm high transparency and superconductivity induction.
• Tunneling spectroscopy reveals a hard induced gap (Δ* = 0.43 meV) in InAs, with substructure indicating influence from both Al and NbTi.
• The two-step proximity effect through the Al layer is crucial for efficient superconductivity transfer.

Outlook:

• Potential for developing novel superconducting InAs-based devices for quantum technologies.
• Further investigation into optimizing the Al interface for enhanced proximity coupling.
• Exploration of this technique for other semiconductor heterostructures and superconductors.