Interacting anyonic fermions in a two-body color code model

Abstract

We introduce a two-body quantum Hamiltonian model of spin 1 2 on a two-dimensional spatial lattice with exact topological degeneracy in all coupling regimes. There exists a gapped phase in which the low-energy sector reproduces an effective color code model. High-energy excitations fall into three families of anyonic fermions that turn out to be strongly interacting. The model exhibits a Z2 × Z2 gauge-group symmetry and string-net integrals of motion, which are related to the existence of topological charges that are invisible to moving high-energy fermions. © 2009 The American Physical Society.