Visualization of Defect-Induced Interband Proximity Effect at the Nanoscale

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Most superconductors exhibit multiband superconductivity, but are often described by single-band theories due to strong interband coupling.
• The complex physics of multiband superconductivity remains experimentally challenging to study.

Purpose of the Study:

• To experimentally investigate and control the interband coupling in a clean limit multiband superconductor.
• To demonstrate the modification of superconducting order parameters by tuning interband coupling.

Main Methods:

• Utilized millikelvin scanning tunneling microscopy to study stacking fault tetrahedra in lead (Pb).
• Locally tuned interband coupling strength from weak to strong.

Main Results:

• Observed the transition of superconducting order parameters from two distinct gaps to a single merged gap.
• Demonstrated local control over interband coupling in a clean limit system.

Conclusions:

• The experiments provide a critical test for theories of multiband superconductivity.
• Offers a pathway to explore predicted quantum effects in multiband superconductors.