Condensed Spin Excitation of Quantized Dirac Fermions in the Quasi-Two-Dimensional Semimetal
Phys. Rev. Lett. 136, 106601 – Published 10 March, 2026
DOI: https://doi.org/10.1103/kx86-56ww
Abstract
Dirac semimetals provide a new platform for the quantum Hall effect at low magnetic fields. In the presence of strong spin-orbit coupling, a spin-split Landau level is expected to enhance the bulk quasiparticle excitation. Here we report NMR spectroscopy that site selectively probes dynamic spin susceptibility on the magnetic semimetal . We find that spontaneous staggered fields from antiferromagnetic Mn moments are completely canceled at the Bi layer hosting Dirac fermions. The nuclear spin-lattice relaxation rate follows the cubic temperature dependence down to low temperatures under the in-plane field, manifesting the chemical potential close to the Dirac point. becomes constant below 20 K under the out-of-plane field, where the well-separated Laudau level appears. The strong anisotropy of exceeding 100 suggests spin-split Landau levels in the quantum Hall regime.
