Nanoscale Domain Wall Engineered Spin-Triplet Josephson Junctions and SQUID

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Spin-singlet Cooper pairs can transform into spin-triplet Cooper pairs at superconductor/ferromagnet interfaces.
• Theoretical models predicted triplet supercurrent generation via ferromagnetic domain walls, but experimental evidence was lacking.
• Accessing single domain walls in ferromagnets for study is challenging.

Purpose of the Study:

• To experimentally demonstrate the generation and transport of spin-triplet supercurrents through a single ferromagnetic domain wall.
• To develop a method for isolating and utilizing a single domain wall as a Josephson barrier.
• To fabricate and test a novel superconducting spintronic device based on this phenomenon.

Main Methods:

• Fabrication of a nanoscale superconductor/ferromagnet/superconductor (S/F/S) planar junction using a patterned ferromagnetic nanoconstriction.
• Utilizing a pinned domain wall within the nanoconstriction as a Josephson barrier.
• Measurement of supercurrent transport across the ferromagnetic barrier.

Main Results:

• Successful demonstration of long-range spin-triplet supercurrents across a ferromagnetic barrier exceeding 70 nm.
• Realization of a single domain wall acting as a functional Josephson barrier.
• Fabrication of a ferromagnetic planar nano-SQUID device comprising two spin-triplet Josephson junctions.

Conclusions:

• The study provides the first experimental evidence of triplet supercurrents mediated by ferromagnetic domain walls.
• The developed nanoconstriction technique allows for the controlled use of domain walls in superconducting devices.
• This work paves the way for advanced superconducting spintronics and quantum information technologies.