Quantum breathers in ferromagnetic chains with on-site easy axis anisotropy

Abstract

Quantum breathers in one-dimensional ferromagnetic chains with on-site easy axis anisotropy are investigated analytically. Based on the Hartree approximation, we can work out the case of quantum breathers with a large number of quanta. By using the multiple-scale method combined with the semidiscrete approximation, the nonlinear Schrödinger equation is derived. It is shown that quantum breathers can exist in the Heisenberg ferromagnetic chain. In addition, we obtain the energy level formula of quantum breathers, which indicates that the energy of such quantum breathers is quantized.