The bismuth-based half-Heusler materials host a nontrivial topological band structure, unconventional superconductivity, and large spin-orbit coupling in a system with very low electron density. In particular, the inversion of p-orbital-derived bands with an effective angular momentum j of up to 3/2 is thought to play a central role in anomalous Cooper pairing in the cubic half-Heusler semimetal YPtBi, which is thought to be the first "high-spin" superconductor. Here, we report an extensive study of the angular dependence of quantum oscillations (QOs) in the electrical conductivity of YPtBi, revealing an anomalous Shubnikov-de Haas effect consistent with the presence of a coherent j=3/2 Fermi surface. The QO signal in YPtBi manifests an extreme anisotropy upon rotation of the magnetic field from the  to  crystallographic direction, where the QO amplitude vanishes. This radical anisotropy for such a highly isotropic system cannot be explained by trivial scenarios involving changes in effective mass or impurity scattering, but rather is naturally explained by the warping feature of the j=3/2 Fermi surface of YPtBi, providing direct proof of active high angular momentum quasiparticles in the half-Heusler compounds.
H. Kim et al., "Quantum Oscillations of the J=3/2 Fermi Surface in the Topological Semimetal Yptbi," Physical Review Research, vol. 4, no. 3, article no. 033169, American Physical Society, Jul 2022.
The definitive version is available at https://doi.org/10.1103/PhysRevResearch.4.033169
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01 Jul 2022