Destruction of Neel order in the cuprates by electron-doping

TL;DR

This paper investigates how Neel antiferromagnetic order is suppressed in electron-doped cuprates, revealing complex quantum phase transitions and proposing experimental ways to distinguish these from traditional spin density wave scenarios.

Contribution

It introduces new theoretical pathways for the destruction of Neel order in cuprates, including topologically ordered phases and unconventional superconducting transitions.

Findings

Identification of a topologically ordered 'doublon metal' phase.

Proposal of unconventional transitions to nematic and valence bond supersolid states.

Guidance for experimental discrimination of these phases via neutron scattering and NMR.

Abstract

Motivated by the evidence in PCCO and NCCO of a magnetic quantum critical point at which Neel 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 Neel state with small electron Fermi pockets, and this yields a fully gapped d_{x^2-y^2} superconductor with co-existing Neel 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 Neel 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 Neel order by neutron scattering or NMR should discriminate these unconventional transitions from spin density wave theory.