Two pieces of work on cuprates

Just to highlight them here, because they seemingly represent something defying the cliche.
1. Electron-spin excitation coupling in an electron-doped copper oxide superconductor [Nphy, 7:719(2011)]

High-temperature (high-Tc) superconductivity in the copper oxides arises from electron or hole doping of their antiferromagnetic (AF) insulating parent compounds. The evolution of the AF phase with doping and its spatial coexistence with superconductivity are governed by the nature of charge and spin correlations, which provides clues to the mechanism of high-Tc superconductivity. Here we use neutron scattering and scanning tunnelling spectroscopy (STS) to study the evolution of the bosonic excitations in electron-doped superconductor Pr0:88LaCe0:12CuO4􀀀 with different transition temperatures (Tc) obtained through the oxygen annealing process.We find that spin excitations detected by neutron scattering have two distinct modes that evolve with Tc in a remarkably similar fashion to the low-energy electron tunnelling modes detected by STS. These results demonstrate that antiferromagnetism and superconductivity compete locally and coexist spatially on nanometre length scales, and the dominant electron–boson coupling at low energies originates from the electron-spin excitations.

2. Intense paramagnon excitations in a large family of high-temperature superconductors [Nphy 7:725(2011)]

In the search for the mechanism of high-temperature superconductivity, intense research has been focused on the evolution of the spin excitation spectrum on doping from the antiferromagnetic insulating to the superconducting state of the cuprates. Because of technical limitations, the experimental investigation of doped cuprates has been largely focused on low-energy excitations in a small range of momentum space. Here we use resonant inelastic X-ray scattering to show that a large family of superconductors, encompassing underdoped YBa2Cu4O8 and overdoped YBa2Cu3O7, exhibits damped spin excitations (paramagnons) with dispersions and spectral weights closely similar to those of magnons in undoped cuprates. The comprehensive experimental description of this surprisingly simple spectrum enables quantitative tests of magnetic Cooper pairing models. A numerical solution of the Eliashberg equations for the magnetic spectrum of YBa2Cu3O7 reproduces its superconducting transition temperature within a factor of two, a level of agreement comparable to that of Eliashberg theories of conventional superconductors.