Abstract
The intrinsic antiferromagnetic topological insulator MnBi2Te4 undergoes a metamagnetic transition in a c-axis magnetic field. It has been predicted that ferromagnetic MnBi2Te4 is an ideal Weyl semimetal with a single pair of Weyl nodes. Here we report measurements of quantum oscillations detected in the field-induced ferromagnetic phase of MnBi2−xSbxTe4, where Sb substitution tunes the majority carriers from electrons to holes. Single-frequency Shubnikov–de Haas oscillations were observed in a wide range of Sb concentrations (0.54≤x≤1.21). The evolution of the oscillation frequency and the effective mass shows reasonable agreement with the Weyl semimetal band structure of ferromagnetic MnBi2Te4 predicted by density functional calculations. Intriguingly, the quantum oscillation frequency shows a strong temperature dependence, indicating that the electronic structure depends sensitively on magnetism.
