Control of topological phase transitions in Dirac semimetal films by exchange fields

The exchange field effects on topological Dirac semimetal(DSM) films are discussed in this article. A topological phase transition can be controlled by tuning the exchange field together with the quantum confinement effects. What is more interesting is that the system can transit into the quantum anomalous Hall(QAH) state from the topologically trivial state(Z_2 = 0) or from the topologically nontrivial state(Z_2 = 1), depending on the thickness of the DSM films. This provides a useful mechanism to realize the QAH state from the DSM.