Identification of Lifshitz transition, quantum oscillations, and metal-insulator transition in a composite topological matter Bi₄(Br_0.2I_0.8)₄

Exploring the electronic transport behavior in the topological matter is of crucial interest in the region of both fundamental research and potential applications. In this work, we perform a systematical investigation of the transport properties of the new discovered topological material with both high-order topological insulating order and strong topological insulating order, Bi₄(Br_0.2I_0.8)₄, by applying the physical properties measurement system. A sign change of charge carriers with the variation of temperature is observed, which is ascribed to the Lifshitz transition and confirmed by the temperature-dependent angle-resolved photoemission spectroscopy measurements. The behavior of Shubnikov-de Hass oscillations occurs at a lower magnetic field region compared to the undoped Bi₄Br₄ parent phase, inferring the shrunk Fermi surface by introducing I dopant. After entering the extreme quantum limit, the metal-insulator transition is evoked by the possible finite electron-electron interaction with the further increment of magnetic field. The relationship among the Lifshitz transition, quantum oscillations, and metal-insulator transition is discussed to resolve the potential mechanism of quantum transport behaviors in Bi₄(Br_0.2I_0.8)₄. Our work provides the important references for modulating the quantum transport properties of topological matters in the future.