Probing k-Space Alternating Spin Polarization via the Anomalous Hall Effect.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Altermagnets are a novel class of collinear magnets with alternating magnetic moments and k-space spin polarization.
• Existing experimental techniques for probing k-space spin polarization in altermagnets are limited.

Purpose of the Study:

• To propose a novel experimental approach for probing the k-space spin polarization of altermagnets.
• To establish Dirac fermions on topological insulator surfaces as a sensitive probe for altermagnet spin characteristics.

Main Methods:

• Interfacing an altermagnet with the surface of a topological insulator.
• Observing the momentum-dependent, sign-alternating Dirac mass imprinted on topological insulator surface states.
• Measuring the Hall conductance to extract local k-space magnetic moments.
• Tuning the Dirac point position with an in-plane magnetic field to map global magnetic moment distribution.

Main Results:

• The altermagnet's k-space spin polarization induces a sign-alternating Dirac mass on topological insulator surface states, breaking time-reversal symmetry.
• An alternating half-quantized anomalous Hall effect is observed as a direct consequence of the engineered Dirac mass.
• The method allows for the extraction of local and mapping of global k-space spin density in altermagnets.

Conclusions:

• The proposed method provides a powerful new tool for characterizing the spin properties of altermagnets.
• Dirac fermions on topological insulator surfaces serve as an effective probe for unveiling the spin characters of altermagnets and other unconventional antiferromagnets.
• This work opens new avenues for exploring and utilizing altermagnetic materials in spintronic devices.