MagDirac · Magnetic Doping of 3D Dirac Semimetals

A new field in condensed matter physics has emerged, dealing with new quantum states of matter originating from non-trivial topologies of the electronic band structure. Topological insulators were the first class of such materials. Dirac and Weyl semimetals are becoming the focus of the next major waive of research on topological matter. In these materials, the bulk valence band and conduction band touch at discrete points and disperse linearly (3D analogues of graphene). This project aims to answer a key fundamental question in this field: can time-reversal symmetry (TRS) breaking induce a Weyl state in a Dirac semimetal? The originality of our project resides on the idea of switching between Dirac and Weyl states using magnetism (TRS breaking), as the ON-OFF switch, instead of inferring the role of TRS by investigating Dirac and Weyl states in different compounds. We will synthesize epitaxial thin films of Cd3As2, the model 3D TDS, and induce a ferromagnetic state via magnetic doping. Subsequently we will perform a thorough investigation of the band structure (Dirac/Weyl cones, surface states and Fermi arcs), aiming to understand the coupling between magnetic and topological states, in particular, the switching between Dirac and Weyl states by breaking and restoring of TRS. In addition to its fundamental interest, this work has the potential to open a new research field dedicated to electrical switching between topological states, to be exploited in Dirac/Weyl-based electronic devices.