Electric field manipulation of spin texture and magnetic response in Dirac semimetals

Dr Son Ho, Research Fellow, RMIT University

Three-dimensional Dirac semimetals (3D DSM) such as Cd₃As₂, Na₃Bi show great potential as the next-generation platform for spintronic devices. The capability of these materials is derived from their key properties including a sizable gap allowing thermal stability at room temperature, and a helical spin texture for non-magnetic manipulation of spin/charge with low energy consumption. Therefore, in realizing the application the DSMs, a systematic understanding of how to control and optimize the above properties is essential.

In this work, in framework of eight-band Kane k.p and variational approach, we establish the effective model to describe the Dirac semimetal films in terms of the underlying factors, i.e., bulk bandstructure (multi-orbital contribution), and tunable heterostructure properties (inversion symmetry breaking, gate voltage, film thickness). Based on the effective model, the topological phase diagram of the system is constructed by deriving the Z2 invariant and the corresponding gap. We find that there exists critical values of thickness and gate voltage for reversing the gap, which corresponds to a phase transition between topologically trivial (Z2=0) and non-trivial (Z2=1) states. Especially, such transition can occur in thin film of few layers, opening possibilities for application in topological transistor devices. Furthermore, the spin texture can be manipulated, leading to tunable spin-charge conversion for spintronics application.