Problem of Two Spin Deviations in a Linear Chain with Next-Nearest-Neighbor Interactions

Abstract

The problem of two spin deviations from the fully aligned state is studied in a linear chain for the Hamiltonian [J(i,j) > 0]: H=−½ ∑ (nn)J(i,j)Si·Sj−½α ∑ (nnn)J(i,j)Si·Sj,where (nn) and (nnn) mean nearest- and next-nearest-neighbor interactions, respectively. The behavior of the bound state, which is found to exist for α ≥ 0 only, is discussed.