Weyl semimetal is a topological state of matter, characterized by the presence of nondegenerate band-touching nodes, separated in momentum space, in its band structure. The consequences of breaking the inversion symmetry in particular realization of a Weyl semimetal: a superlattice heterostructure, made of alternating layers of topological insulator and normal insulator materials will be discussed. This generally moves the Weyl nodes to different energies, thus eliminating nodal semimetal and producing a state with electron and hole Fermi surfaces.
We demonstrate that a new phenomenon arises in this case, if an external magnetic field along the growth direction of the heterostructure is applied. Namely, this leads to an equilibrium dissipationless current, owing along the direction of the field, whose magnitude is proportional to the energy difference between the Weyl nodes and to the magnetic field, with a universal coefficient, given by a combination of fundamental constants.