Spontaneous coherent phonons in the ground state of strong spin-phonon interaction

Abstract

By the use of a simple model, the structure of the ground state of the strong spin-phonon interaction is studied. It is shown that the ground state of the system is very different from the state with no spin-phonon excitations. By second-order perturbation theory among degenerate states it is possible to see that the new ground state is populated by coherent running lattice waves associated to correlated spin waves. Some of the physical implications of this structure are discussed. It is suggested that the validity of the model is not limited to magnetoelastic problems.