Altermagnetic Magnons in Twisted van der Waals Antiferromagnets

Area of Science:

• Condensed Matter Physics
• Spintronics
• Materials Science

Background:

• Magnonics offers low-dissipation information processing but requires external fields for spin-polarized transport.
• Altermagnets possess spin-polarized electronic states without net magnetization, yet achieving significant magnon spin splitting and currents is difficult.

Purpose of the Study:

• To explore twisted van der Waals antiferromagnets as a tunable platform for altermagnetic magnons.
• To investigate methods for achieving large magnon spin splitting and robust magnonic spin currents without external magnetic fields.

Main Methods:

• Utilized symmetry analysis of twisted van der Waals antiferromagnets (CrPS4 and CrI3 bilayers).
• Investigated the impact of breaking specific symmetries on magnon spin splitting.
• Characterized field-free spin currents, including spin Seebeck and spin Nernst effects.

Main Results:

• Demonstrated symmetry-tunable nonrelativistic magnon spin splitting in twisted bilayers lacking inversion and horizontal mirror symmetries.
• Showed that breaking out-of-plane rotational symmetries enhances low-energy magnon splittings.
• Observed pronounced field-free spin currents in twisted CrPS4, with spin transport efficiently tuned by twist angle and exceeding conventional altermagnets.

Conclusions:

• Twisted van der Waals antiferromagnets provide a novel platform for controlling altermagnetic magnons.
• This approach enables efficient, field-free spin transport, significantly advancing altermagnetic spintronics.
• The findings deepen the fundamental understanding of magnon control and spintronic applications.