Zeeman splitting and quantum-limit magnetoresistance anomaly in the topological insulator β-Ag2Se

Topological insulators (TIs) represent a unique class of materials with significant potential for both fundamental research and future applications. The characteristic band inversion in TIs gives rise to unique properties in their bulk states. In this paper, we report exotic features of nontrivial bulk states in a TI beta-Ag2Se. The investigated crystals exhibit resistivity-temperature behavior characteristic of doped semiconductors, with a band gap that aligns well with theoretical electronic structure calculations. Systematic magnetotransport measurements reveal a three-dimensional (3D) anisotropic Fermi pocket resulting from electron doping, indicating that bulk states predominantly contribute to the observed properties. Under parallel magnetic and electric fields, Zeeman splitting is observed, giving a Land & eacute; g factor of similar to 10. Furthermore, we detect anomalous longitudinal magnetoresistance (MR) dips in the quantum limit when only the lowest Landau level is occupied, which are closely related to the field-induced topological phase transition and reminiscent of the forbidden backscattering in TIs due to the spinor orthogonality. These intriguing transport phenomena combined with theoretical calculations elucidate the topological nature of beta-Ag2Se as a TI and offer a promising foundation for developing TI-based devices.