Spin-Polarized Josephson Supercurrent in Nodeless Altermagnets

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Long-range propagation of equal-spin triplet Cooper pairs is typically observed in ferromagnet-superconductor junctions, relying on net magnetization.
• Existing Josephson junctions primarily utilize spin-singlet pairing or require magnetic fields.

Purpose of the Study:

• To propose and investigate a novel mechanism for Josephson supercurrents mediated exclusively by spin-triplet pairings.
• To identify suitable material platforms for achieving magnetization-free spin-triplet supercurrents.

Main Methods:

• Theoretical proposal of Josephson junctions based on collinear altermagnets, specifically nodeless altermagnets.
• Analysis of spin-split Fermi surfaces and spin-valley polarization in these materials.
• Investigation of Cooper pair correlations and control over 0-π transitions.

Main Results:

• Identified nodeless altermagnets as ideal platforms for generating Josephson supercurrents via spin-triplet pairing without net magnetization.
• Demonstrated that these junctions sustain supercurrents through spin-up and spin-down Cooper pairs from different valleys.
• Showcased robust 0-π transitions and tunable singlet-triplet mixing by controlling interface properties and junction orientation.

Conclusions:

• Nodeless altermagnets provide a unique platform for realizing magnetization-free, spin-polarized supercurrents.
• This work establishes a new paradigm for spintronic devices and superconducting applications.
• The findings pave the way for novel functionalities in Josephson junctions based on altermagnetic materials.