Quantum anomalous Hall effect with field-tunable Chern number near Z2 topological critical pointWei-Feng Tsai1,2,3*, Le Quy Duong2,3, Hsin Lin2,3, Y. P. Feng2,31Physics, National Sun Yat-sen University, Kaohsiung, Taiwan2Physics, National University of Singapore, Singapore, Singapore3Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore* presenting author:Wei-Feng Tsai, email:wftsai@mail.nsysu.edu.twWe study the practicability of achieving quantum anomalous Hall (QAH) effect with field-tunable Chern number in a magnetically doped, topologically trivial insulating thin film. Specifically in a candidate material, TlBi(S$_{1-\delta}$Se$_{\delta}$)$_2$, we demonstrate that the QAH phases with different Chern numbers can be achieved by means of tuning the exchange field strength or the sample thickness near the Z2 topological critical point. Our physics scenario successfully reduces the necessary exchange coupling strength for a targeted Chern number. This QAH mechanism differs from the traditional QAH picture with a magnetic topological insulating thin film, where the“surface” states must involve and sometimes complicate the realization issue. Furthermore, we find that a given Chern number can also be tuned by a perpendicular electric field, which naturally occurs when a substrate is present.Keywords: topological insulator, quantum anomalous Hall effect, Chern number