a, Low-field oscillations of Rxx. The inset shows the corresponding Landau fan diagrams, the fitting curves of which have the same slope. The oscillation frequency is unchanged when measured at different terminals, as indicated by the parallel dashed black lines, suggesting that the Landau-level shift is not induced by the change in the size of the Fermi surface. The low-field oscillations are used to extract the Landau-level index. b, Hall resistance as a function of 1/B. c, Comparison of the Hall resistance Rxy at positive and negative magnetic fields for terminals 1–2, which is field-symmetric. d, Temperature dependence of Rxx. Small oscillation features are observed at very low temperature (below 1 K). Considering their periodicity and carrier mobility, and given that there is no corresponding feature in Rxy, these oscillations are not from the fractional quantum Hall effect. They probably come from regimes with different thickness, the Landau levels of which are shifted by the thickness-dependent phase term. e, Stack view of bulk quantum oscillations with in-plane magnetic field measured at different terminals of sample 1.