Tunable double-Weyl Fermion semimetal state in the SrSi2 materials class

We discuss first-principles topological electronic structure of noncentrosymmetric SrSi 2 materials class based on the hybrid exchange-correlation functional. Topological phase diagram of SrSi 2 is mapped out as a function of the lattice constant with focus on the semimetal order. A tunable double-Weyl Fermion state in Sr 1− x Ca x Si 2 and Sr 1− x Ba x Si 2 alloys is identified. Ca doping in SrSi 2 is shown to yield a double-Weyl semimetal with a large Fermi arc length, while Ba doping leads to a transition from the topological semimetal to a gapped insulator state. Our study indicates that SrSi 2 materials family could provide an interesting platform for accessing the unique topological properties of Weyl semimetals.