Experimental Realization of a Three-Dimensional Dirac Semimetal

Understand

The three dimensional (3D) Dirac semimetal, which has been predicted theoretically, is a new electronic state of matter.

• It can be viewed as 3D generalization of graphene, with a unique electronic structure in which conduction and valence band energies touch each other only at isolated points in momentum space (i.e.
• the 3D Dirac points), and thus it cannot be classified either as a metal or a semiconductor.
• In contrast to graphene, the Dirac points of such a semimetal are not gapped by the spin-orbit interaction and the crossing of the linear dispersions is protected by crystal symmetry.