A new kind of topological quantum order: A dimensional hierarchy of quasiparticles built from stationary excitations

Exactly solvable models often provide valuable insights in theoretical studies of topological phases. Here the authors introduce exactly solvable models of interacting Majorana fermions each with extensive topological ground-state degeneracy and a hierarchy of pointlike, topological excitations that are only free to move within submanifolds of the full lattice. These very different models make up a new kind of topological quantum order.