Double Dirac Semimetals in Three Dimensions

TL;DR

This paper explores the theoretical existence of double Dirac semimetals in three dimensions, identifying specific space groups capable of hosting such states and analyzing their topological properties and potential material realizations.

Contribution

It introduces explicit models for double Dirac semimetals in certain space groups and demonstrates their topological phases and defect-bound modes.

Findings

7 space groups can host double Dirac points

Space group 135 can host an intrinsic double Dirac semimetal

Uniaxial strain induces topologically distinct insulating phases

Abstract

We study a class of Dirac semimetals that feature an eightfold-degenerate double Dirac point. We show that 7 of the 230 space groups can host such Dirac points and argue that they all generically display linear dispersion. We introduce an explicit tight-binding model for space groups 130 and 135, showing that 135 can host an intrinsic double Dirac semimetal -- one with no additional degeneracies at the Fermi energy. We consider symmetry-lowering perturbations and show that uniaxial compressive strain in different directions leads to topologically distinct insulating phases. In addition, the double Dirac semimetal can accommodate topological line defects that bind helical modes. Potential materials realizations are discussed.