1212.4202 (Jing-Min Hou)

Protection of Weyl Semimetals in Optical Lattices by
Gauge-Color-Translation Symmetry    [PDF]

Jing-Min Hou

We study three tight-binding models of two-dimensional fermionic optical lattices. We find that these systems have a novel composite symmetry, i.e. gauge-color-translation (GCT) symmetry, which consists of a fixed translation transformation, a color transformation and a fixed local U(1) gauge transformation. The corresponding symmetry operator is antiunitary. We predict that, due to the protection of GCT symmetry, the conduction and valence bands are degenerate at some isolated momenta. These degenerate points form Weyl nodes in the Brillouin zone. The quasiparticles and quasiholes near the Weyl nodes can be considered as Weyl fermions and have chirality characterized by a winding number. With the protection of GCT symmetry and the winding number, the Weyl nodes occur in a very large range of parameters.

View original: http://arxiv.org/abs/1212.4202