The effect of interaction and gauge field in topological semimetals

Topological semimetals possess topologically protected nodal points or lines with exotic physical properties. Here I focus on the effects of interaction and gauge field on topological Weyl or Dirac semimetals. I will first show that in a nanowire made of Dirac semimetals, interaction enables the emergence of boundary Majorana zero modes that are protected by rotation symmetry under magnetic fields. Therefore, the Dirac semimetal nanowire provides an ideal platform for the realization of 1D interacting topological phase with Majorana physics, which does not require superconductivity and is thus number-conserving. Next I will describe the influence of generalized gauge fields in Weyl semimetals. Due to the chirality of Weyl nodes, it was realized that more general form of gauge fields beyond conventional electromagnetic fields can be induced by magnetic fluctuation or strain in Weyl semimetals. As a consequence of gauge fields, zeroth Landau levels can be induced and only propagate in one direction (chiral). The presence of chiral zeroth Landau levels is the origin of chiral anomaly and allows for a robust bulk transport. Such generalization of gauge fields is recently demonstrated in an inhomogeneous Weyl metamaterial experimentally.

I acknowledge the support from ONR under No. N00014-18-1-2793, DOE under award No. DE-SC0019064 and Charles E. Kaufman Foundation.