Multiflavor String-Net Models

We generalize the string-net construction to multiple flavors of strings, each of which is labeled by the elements of an Abelian group ${G}_{i}$. The same flavor of strings can branch, while different flavors of strings can cross one another and thus they form intersecting string nets. We systematically construct the exactly soluble lattice Hamiltonians and the ground-state wave functions for the intersecting string-net condensed phases. We analyze the braiding statistics of the low-energy quasiparticle excitations and find that our model can realize all the topological phases as the string-net model with group $G={\ensuremath{\prod}}_{i}{G}_{i}$. In this respect, our construction provides various ways of building lattice models which realize topological order $G$, corresponding to different partitions of $G$ and thus different flavors of string nets. In fact, our construction concretely demonstrates the K\"unneth formula by constructing various lattice models with the same topological order. As an example, we construct the $G={\mathbb{Z}}_{2}\ifmmode\times\else\texttimes\fi{}{\mathbb{Z}}_{2}\ifmmode\times\else\texttimes\fi{}{\mathbb{Z}}_{2}$ string-net model which realizes a non-Abelian topological phase by properly intersecting three copies of toric codes.