Destruction of Néel order in the cuprates by electron doping

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

Motivated by the evidence in Pr_2-xCeₓCuO_4-y and Nd_2-xCeₓCuO_4-y of a magnetic quantum critical point at which N\'eel order is destroyed, we study the evolution with doping of the $T=0$ quantum phases of the electron-doped cuprates. At low doping, there is a metallic N\'eel state with small electron Fermi pockets, and this yields a fully gapped d_x²-y² superconductor with coexisting N\'eel order at low temperatures. We analyze the routes by which the spin-rotation symmetry can be restored in these metallic and superconducting states. In the metal, the loss of N\'eel order leads to a topologically ordered ``doublon metal'' across a deconfined critical point with global O(4) symmetry. In the superconductor, in addition to the conventional spin-density wave transition, we find a variety of unconventional possibilities, including transitions to a nematic superconductor and to valence-bond supersolids. Measurements of the spin-correlation length and of the anomalous dimension of the N\'eel order by neutron scattering or NMR should discriminate these unconventional transitions from spin-density wave theory.