Weyl semimetals in optical lattices: moving and merging of Weyl points, and hidden symmetry at Weyl points

摘要

We propose to realize Weyl semimetals in a cubic optical lattice. We findthat there exist three distinct Weyl semimetal phases in the cubic opticallattice for different parameter ranges. One of them has two pairs of Weylpoints and the other two have one pair of Weyl points in the Brillouin zone.For a slab geometry with (010) surfaces, the Fermi arcs connecting theprojections of Weyl points with opposite topological charges on the surfaceBrillouin zone is presented. By adjusting the parameters, the Weyl points canmove in the Brillouin zone. Interestingly, for two pairs of Weyl points, as onepair of them meet and annihilate, the originial two Fermi arcs coneect intoone. As the remaining Weyl points annihilate further, the Fermi arc vanishesand a gap is opened. Furthermore, we find that there always exists a hiddensymmetry at Weyl points, regardless of anywhere they located in the Brillouinzone. The hidden symmetry has an antiunitary operator with its square being$-1$.