Evidence for magnon bound-state excitations in the quantum chain system (C6H11N3)CuCl3

Abstract

Ferromagnetic resonance measurements are presented on the quasi-one-dimensional S=1/2ferromagnetic compound (C6H11NH3)CuCl3(CHAC), indicating the existence of magnon bound-state resonances (MBR). In addition to the normal ferromagnetic resonances several extra modes were observed in the temperature region 1.2K<T<4.2K and at various frequencies (18 GHz< nu <75 GHz). It is shown that these extra resonances can be interpreted in terms of Delta m=+or-1 transitions between magnon bound states. The experimental results are compared with three theoretical models: the S=1/2ferromagnetic xxz and xyz models and a semiclassical model which shows the possibility of inducing transitions between envelope soliton states in ferromagnetic resonance experiments. The three models give qualitatively similar results for the low-lying excited states of the magnetic chains in CHAC. The experimental results can be described best by the S=1/2ferromagnetic xyz model.