Universal properties of modulated antiferromagnetic systems
  Magnetism and superconductivity are physical phenomena whose foundations are rooted in quantum mechanics and whose technological applications do not cease to surprise us. In this article we describe a class of magnetic materials, we call modulated antiferromagnetic systems (MAS), that has a prominent representative in the copper-oxide high-temperature superconductors. The class, however, is not exclusive to these superconductors. Indeed, several materials that belong to that class are insulators. The magnetic spectral weight of MAS displays the following universal properties: a local intensity maximum (resonance peak) at the commensurate antiferromagnetic wave vector; peaks at the nearly-antiferromagnetic wave vectors for excitation energies well below the resonance, and at wave vectors rotated by 45 degrees for energies above resonance. Moreover, we predict an observable rotation by 45 degrees of the peaks immediately below the resonance. All these universal signatures, condensed in a twisted hour-glass-like spectrum, are merely consequences of the unique topological characteristics of the single-particle magnetic dispersion relation. We thus provide a unifying scenario that explains the phenomenology that has been observed in inelastic neutron scattering experiments of the high-temperature superconductors. 
C.D. Batista, G. Ortiz, and A.V. Balatsky