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Tunable topological Weyl semimetal from simple cubic lattices with staggered fluxes

Three-dimensional Weyl fermions are found to emerge from simple cubic lattices with staggered fluxes. The mechanism is to gap the quadratic band touching by time-reversal-symmetry-breaking hoppings. The system exhibits rich phase diagrams where the number of Weyl fermions and their topological charge are tunable via the plaquette fluxes. The Weyl semimetal state is shown to be the intermediate phase between non-topological semimetal and quantum anomalous Hall insulator. The transitions between those phases can be understood through the evolution of the Weyl points as Berry flux insertion processes. As the Weyl points move and split (or merge) through tuning the plaquette fluxes, the Fermi arcs and surface states undergo significant manipulation. We also propose a possible scheme to realize the model in ultracold fermions in optical lattices with artificial gauge fields.