Nontrivial Berry's phase and exotic quantum phenomena in the vicinity of the quantum limit in the three-dimensional Dirac system Bi0.97Sb0.03

Quantum oscillations are known as the manifestation of the Fermi surface of metals in the presence of a strong magnetic field and of associated geometrical phases such as Berry's phase, playing a critical role in topological quantum materials. This study reports quantum oscillations on the three-dimensional (3D) Dirac material Bi0.97Sb0.03 single crystals in pulsed magnetic fields up to 50 T with three possible orientations. Under a magnetic field, we observe very pronounced Shubnikov-de Haas (SdH) oscillations originating from the Landau quanti-zation of T-point holes. The SdH oscillations were well indexed with a large Lande ' g factor. The anisotropic behaviors of the Lande ' g factor were also deduced based on a detailed analysis of SdH oscillations. The Landau fan diagram revealed a nontrivial Berry's phase. Beyond the quantum limit (QL) under an extremely strong magnetic field, unusual quantum oscillations (UQO) were found. The possible origin of this phenomenon may be electronic instability caused by interactions. These results offer insights into the unusual electronic properties under the extremely strong fields caused by the unique band topology in this case.