  A family of topological semimetallic phases where twofold degenerate gapless
points form linked rings is introduced. We refer to this phase as Weyl-link
semimetals. A concrete two-band model with two linked nodal lines is
constructed. We demonstrate that the Chern-Simons 3-form depends on the linking
number of rings in a generic two-band model. In addition, we show the emergence
of zero-energy modes in the Landau level spectrum can reveal the location of
nodal lines, providing a method of probing their linking number.
