Relativistic Spin-Momentum Locking in Altermagnets

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Spin-momentum locking, crucial for spintronics, has been studied in the nonrelativistic limit.
• Altermagnets exhibit unique magnetic and electronic properties due to their crystal structure and magnetic ordering.
• Spin-orbit coupling introduces antisymmetric exchange interactions, leading to spin canting in magnetic materials.

Purpose of the Study:

• To investigate relativistic spin-momentum locking in altermagnets by including spin-orbit coupling.
• To analyze the impact of antisymmetric exchange interactions and spin canting on spin-momentum locking.
• To explore the specific characteristics of relativistic spin-momentum locking in orthorhombic YVO3 and hexagonal MnTe.

Main Methods:

• Theoretical investigation of spin-momentum locking in altermagnetic systems.
• Analysis of spin-orbit coupling effects on electronic band structure and spin polarization.
• Characterization of spin-momentum locking in terms of different angular momentum components (s-, d-waves).

Main Results:

• Relativistic spin-momentum locking in YVO3 comprises s-, dxy-, and dxz-wave components.
• In MnTe, the dominant Sy component retains nonrelativistic g-wave locking, but symmetry breaking lowers it to d-wave.
• Relativistic spin-momentum locking in MnTe is composed of dxz-, dyz-, and s-wave components.
• Canted spin components, though small in real space, significantly contribute to k-space properties.

Conclusions:

• Spin-orbit coupling and antisymmetric exchange fundamentally alter spin-momentum locking in altermagnets, leading to relativistic effects.
• The symmetry of the crystal structure and the orientation of the Néel vector dictate the specific form of relativistic spin-momentum locking.
• Relativistic spin-momentum locking in altermagnets has significant implications for charge and spin transport phenomena, including spin-Hall conductivity and spin photocurrents.