  Weyl semimetals and nodal line semimetals are characterized by linear band
touching at zero-dimensional points and one-dimensional lines, respectively. We
predict that a circularly polarized light drives nodal line semimetals into
Weyl semimetals. The Floquet Weyl points thus obtained are tunable by the
incident light, which enables investigations of them in a highly controllable
manner. The transition from nodal line semimetals to Weyl semimetals is
accompanied by the emergence of a large and tunable anomalous Hall
conductivity. Our predictions are experimentally testable by transport
measurement in film samples or by pump-probe angle-resolved photoemission
spectroscopy.
