Geometry-controlled engineering of the low-temperature proximity effect in normal metal-superconductor junctions

Area of Science:

• Condensed matter physics
• Superconductivity
• Materials science

Background:

• The proximity effect describes the influence of a superconductor on an adjacent normal metal.
• At finite temperatures, proximity effect decays exponentially, but at low temperatures, it follows a power law dependent on dimensionality.
• Understanding factors influencing proximity effect is crucial for superconducting hybrid devices.

Purpose of the Study:

• To investigate the impact of normal metal-superconductor (NS) junction geometry on the proximity effect.
• To determine how interface curvature affects the spatial propagation of superconducting order.
• To explore the relationship between NS interface geometry, junction transparency, and the proximity effect.

Main Methods:

• Theoretical analysis of the proximity effect in ballistic NS junctions.
• Investigation of the role of interface curvature (positive and negative) on the Cooper pair wave function decay.
• Examination of how NS interface geometry influences junction transparency.

Main Results:

• Geometric factors, particularly interface curvature, significantly alter the decay exponent of the superconducting order.
• Negative interface curvature increases the proximity range exponent, extending the superconducting influence.
• Positive interface curvature shortens the proximity range exponent, reducing the superconducting influence.

Conclusions:

• NS junction geometry is a critical factor in modulating the proximity effect.
• Interface curvature directly influences the decay rate of superconductivity in adjacent normal metals.
• These findings are vital for optimizing the design and performance of superconducting hybrid devices.