Orbital-spin Locking and its Optical Signatures in Altermagnets

• Main Authors: Vila, Marc, Sunko, Veronika, Moore, Joel E
• Format: Journal Article
• Language: English
• Published: 30-10-2024
• Subjects: Physics - Materials Science; Physics - Mesoscale and Nanoscale Physics
• DOI: 10.48550/arxiv.2410.23513

Altermagnets, magnetic materials with zero magnetization and spin-split band
structure, have gained tremendous attention recently for their rich physics and
potential applications. Here, we report on a microscopic tight-binding model
that unveils a unique coupling between orbitals and spins in $d$-wave
altermagnets which gives rise to momentum-dependent and spin-selective optical
absorption. This coupling promotes the controlled optical excitation of up or
down spins depending on the polarization direction of linearly polarized light.
Such an effect originates from the coupling of orbitals to the sublattice
degree of freedom through the crystal field, which is then coupled to spins
through the antiferromagnetic interaction. Our crystal field analysis, which is
general to any type of altermagnet, helps understand the onset of
altermagnetism from a microscopic point of view, and we use our results to
propose clear magneto-optical signatures of our predictions. Our findings shine
light on the interplay between orbitals and spins in altermagnets, thus paving
the way towards novel orbitronic and opto-spintronic devices.