Discovery of Fractionalized Neutral Spin-1/2 Excitation of Topological Order

Abstract

After the discovery of fraction quantum Hall states in the 1980s,[1] it became more and more clear that Landau symmetry breaking theory does not describe all possible quantum phases of matter. The new quantum phases of matter were called topologically ordered phases[2,3] (for gapped cases) or quantum ordered phases[4] (for gapless cases), which correspond to patterns of many-body entanglement.[5–7] One may wonder: besides quantum Hall systems, are there other systems that realize the new topological/quantum order?