Resonance peak and incommensurate response as direct manifestations of magnetism

It is argued that both the resonance peak and low-energy incommensurate res ponse observed in high-T-c cuprate superconductors have a common magnetic o rigin. These physical quantities represent universal signatures of an under lying incommensurate spin state both below and above the superconducting tr ansition temperature. In this framework the resonance peak is the reflectio n of commensurate antiferromagnetism. Our theoretical scenario gives an acc ount of the main universal features observed in various families of superco nductors and predicts those that have not been observed yet experimentally. (C) 2001 Elsevier Science B.V. All rights reserved.