Creation of equal-spin triplet superconductivity at the Al/EuS interface

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Conventional superconductors feature Cooper pairs with opposite electron spins.
• Exotic spin-triplet superconductivity can emerge at interfaces between superconductors and ferromagnets.
• Equal-spin triplet pairs are key for advancing low-dissipation spintronics.

Purpose of the Study:

• To provide spectroscopic evidence for the existence of equal-spin triplet pairs.
• To identify a unique signature for detecting these exotic pairs.
• To investigate spin-mixing effects at superconductor-ferromagnet interfaces.

Main Methods:

• Development of a theoretical model predicting a characteristic gap structure.
• Utilizing scanning tunneling spectroscopy to measure the local density of states.
• Experimental demonstration of spin-mixing at the Aluminum/Europium Sulfide (Al/EuS) interface.

Main Results:

• A theoretical model identified a distinct gap structure in the quasiparticle density of states as a signature for equal-spin triplet pairs.
• Scanning tunneling spectroscopy confirmed this signature, providing direct evidence for their presence.
• The Al/EuS interface demonstrated strong and tunable spin-mixing due to spin-dependent transmission.

Conclusions:

• The study provides the first spectroscopic evidence for equal-spin triplet pairs.
• The findings pave the way for novel spintronic devices utilizing these exotic superconducting states.
• Interface engineering, like that in Al/EuS, is crucial for controlling and utilizing spin-triplet superconductivity.