Mechanisms of normal reflection at metal interfaces studied by Andreev-reflection spectroscopy

TL;DR

This study uses Andreev-reflection spectroscopy to investigate the mechanisms of normal reflection at metal interfaces, finding that Fermi-surface mismatch is not the main cause of reflection, thus constraining possible explanations.

Contribution

It provides a detailed analysis showing that Fermi-surface mismatch is not the dominant mechanism of normal reflection at metal interfaces, refining understanding of interface physics.

Findings

Normal reflection strength varies only slightly across different contacts.

Fermi-surface mismatch is not the primary reflection mechanism.

Implications for models of electron transport at interfaces.

Abstract

Andreev-reflection spectroscopy of elemental superconductors in contact with non-magnetic normal metals reveals that the strength of normal-reflection varies only slightly. This observation imposes strong constrictions on the three possible normal-reflection mechanisms: tunneling through a dielectric barrier, reflection due to the different electronic properties of the two electrodes, and diffusive transport caused by elastic scattering in the contact region. We discuss in detail the role played by Fermi-surface mismatch, represented by the different Fermi velocities on both sides of the contact interface. We find that it is at least not the dominant mechanism and possibly completely absent in the Andreev-reflection process.