Hidden order in the cuprates

This is the authors' abstract. We don't add key points for this paper.

We propose that the enigmatic pseudogap phase of cuprate superconductors is characterized by a hidden broken symmetry of d_x²-y²-type. The transition to this state is rounded by disorder, but in the limit that the disorder is made sufficiently small, the pseudogap crossover should reveal itself to be such a transition. The ordered state breaks time-reversal, translational, and rotational symmetries, but it is invariant under the combination of any two. We discuss these ideas in the context of ten specific experimental properties of the cuprates, and make several predictions, including the existence of an as-yet undetected metal-metal transition under the superconducting dome.