Until the late 1980s, phases of matter were understood in terms of Landau's symmetry breaking theory. Following the discovery of the quantum Hall effect the introduction of a second class of phases, those with topological order, was necessary. Phase transitions within the first class of phases involve a change in symmetry, whereas those between topological phases require a change in topological order. However, in rare cases transitions may occur between the two classes in which the vanishing of the topological order is accompanied by the emergence of a broken symmetry. Here, we report the existence of such a transition in a two-dimensional electron gas hosted by a GaAs/AlGaAs crystal. When tuned by hydrostatic pressure, the ν=5/2 fractional quantum Hall state, believed to be a prototype non-Abelian topological phase, gives way to a quantum Hall nematic phase. Remarkably, this nematic phase develops spontaneously, in the absence of any externally applied symmetry breaking fields.
@article{arxiv.1509.03658,
title = {Observation of a transition from a topologically ordered to a spontaneously broken symmetry phase},
author = {N. Samkharadze and K. A. Schreiber and G. C. Gardner and M. J. Manfra and E. Fradkin and G. A. Csáthy},
journal= {arXiv preprint arXiv:1509.03658},
year = {2016}
}