What it is
Researchers show that magnetic quantum oscillation measurements provide a high-resolution, bulk-sensitive, 3D mapping of the order parameter in the unconventional magnet CrSb. Rotating a magnetic field through high- and low-symmetry directions of the CrSb Brillouin zone reveals that the altermagnetic band structure reduces the symmetry of each spin-split Fermi sheet away from nodal orientations. In momentum space, the exchange splitting between up- and down-spins follows the profile of the yz(3x²-y²) real spherical harmonic, the pattern of a hydrogen g-orbital. The work establishes CrSb as a prototypical g-wave metallic altermagnet.
Why it matters
Order parameter symmetry is notoriously difficult to resolve in unconventional superconductors, leaving the analogous symmetry of altermagnets, in which up- and down-spin species have non-degenerate Fermi surfaces, hard to measure directly. Quantum oscillatory quasiparticle spectroscopy provides a bulk-sensitive probe that maps this symmetry across the 3D Brillouin zone.
How to read this
It demonstrates that the order parameter symmetry of unconventional magnets can be precisely mapped by quantum oscillation measurements, giving a route to characterize g-wave and other altermagnets by the shape of their spin splitting.
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