Inhomogeneous superconductivity induced in a ferromagnet by proximity effect

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Proximity effect in superconductor-ferromagnet heterostructures is crucial for understanding emergent phenomena.
• Superconducting order parameter modulation in magnetic materials is a key area of research.

Purpose of the Study:

• To investigate the behavior of the superconducting order parameter in ferromagnetic thin films induced by the proximity effect.
• To analyze the influence of spin-split bands in ferromagnets on Cooper pair dynamics.

Main Methods:

• Planar tunneling spectroscopy was employed to probe the superconducting properties.
• Analysis of damped oscillations in the superconducting order parameter.

Main Results:

• Damped oscillations of the superconducting order parameter were observed in ferromagnetic thin films.
• Oscillations are attributed to momentum transfer from spin-split bands in the ferromagnet.
• A "pi state" (inverted tunneling spectra) occurs for negative superconducting order parameter values.

Conclusions:

• The spin-split bands in ferromagnets directly influence Cooper pair momentum and induce oscillatory behavior.
• The observed "pi state" is a direct consequence of the interplay between superconductivity and ferromagnetism.
• Oscillation damping and period are governed by a spin-polarization-dependent length scale.