Theory of the magnetic excitations in the Cu-O superconductors

Abstract

We show that the recent neutron-scattering data of Shirane et al. on large, superconducting ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ single crystals can be explained in a model with bosonic spins. A part of the spin system Bose condenses at incommensurate k points, resulting in a spiral spin structure. The rest of the spin system goes into a pair condensate, whose excitations describe the spin excitations of the spiral state. Some suggestions for experimental tests are given.