Giant Spin Splitting and Anisotropic Spin Polarization in 2D Altermagnet Cr<sub>2</sub>O.
basic_science · Level V
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- Record sourced from PubMed, PMID 41187109.
- Also identified by DOI 10.1021/acs.nanolett.5c04779.
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Abstract
In this work, we theoretically propose a novel 2D nonvan der Waals (non-vdW) monolayer Cr<sub>2</sub>O, exfoliated from the bulk CrO along the [001] direction. Combining first-principles calculations, spin group symmetry analysis, and Monte Carlo simulations, we reveal that Cr<sub>2</sub>O has exceptional altermagnetic metallic characteristics, featuring a record nonrelativistic spin splitting of 1.83 eV, a high Néel temperature of 507 K, and full spin polarization along specific Γ-X/Γ-Y paths. The spin splitting feature in Cr<sub>2</sub>O exhibits an anisotropic <i>d</i>-wave-like pattern, arising from nontrivial spin-group symmetry operations <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>[</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msub><mo>∥</mo><msubsup><mrow><mover><mi>C</mi><mo>¯</mo></mover></mrow><mrow><mn>4</mn><mi>z</mi></mrow><mrow><mo>±</mo></mrow></msubsup><mo>]</mo></math> that govern direction-dependent spin polarization. Moreover, Boltzmann transport calculations show that the spin polarization <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>S</mi><mi>P</mi></mrow><mrow><mover><mi>n</mi><mo>^</mo></mover></mrow></msub></math> reaches up to 95.2% along principal axes and follows a cosine-like angular dependence in the 2D plane. It remains above 80% across a wide energy range, ensuring robust spin filtering. These results establish Cr<sub>2</sub>O as a promising platform for spin-symmetry-engineered transport in 2D non-vdW altermagnets.