Breakthrough in altermagnetism reveals spin-split Fermi surface in CrSb
Breakthrough in altermagnetism reveals spin-split Fermi surface in CrSb
Breakthrough in altermagnetism reveals spin-split Fermi surface in CrSb
Scientists have uncovered strong evidence of a spin-split Fermi surface in the altermagnetic material CrSb. The breakthrough, published in Nature in 2022, was led by S. Khim's research team, including experts from the Max Planck Institute for Chemical Physics of Solids. Their findings confirm a key theoretical prediction and could shape the development of future electronic devices based on altermagnets.
The team used high magnetic fields and millikelvin temperatures to measure quantum oscillations in CrSb via the de Haas-van Alphen (dHvA) effect. These experiments revealed multiple oscillation frequencies, each linked to four distinct spin-non-degenerate bands. Magnetic torque measurements, carried out on flux-grown crystals with a micro cantilever at NIMS, further supported the observations.
Advanced calculations played a crucial role in the study. Researchers performed fully relativistic electronic band-structure simulations, incorporating spin-orbit coupling (SOC) through the PBE-GGA potential within the DFT+U framework, using the Wien2k code. The inclusion of SOC was vital, as it altered cyclotron orbits by opening gaps where Fermi surface sheets crossed nodal planes—matching the behaviour seen in CrSb.
The analysis showed that bands-1 and -2 featured tubular Fermi surfaces along the ΓA line, paired with closed pockets at the A point. These results aligned with earlier ARPES studies. Meanwhile, bands-3 and -4 displayed unique properties, contributing to the complex oscillation patterns detected. Electrical currents were applied along the c-axis for flux-grown crystals and the a-axis for CVT-grown samples, ensuring precise resistivity measurements.
The confirmation of a spin-split Fermi surface in CrSb provides a solid foundation for testing theoretical models of altermagnetism. It also opens up possibilities for designing new devices that exploit the unusual electronic properties of these materials. The study's combination of high-field experiments and detailed calculations sets a benchmark for future research in this emerging field.
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