Dimerization process and elementary excitations in spin–Peierls chains coupled byfrustrated interactions

Abstract

We consider the ground state and the elementary excitations of an array of spin–Peierlschains coupled by elastic and magnetic interactions. It is expected that the effect of themagnetic interchain coupling will be to reduce the dimerization amplitude and that of theelastic coupling will be to confine the spin one-half solitons corresponding to each isolatedchain. We show that this is the case when these interactions are not frustrated. On theother hand, in the frustrated case we show that the amplitude of dimerization in theground state is independent of the strength of the interchain magnetic interactionin a broad range of values of this parameter. We also show that free solitonscould be the elementary excitations when only nearest neighbour interactions areconsidered. The case of an elastic interchain coupling is analysed on a generalenergetic consideration. To study the effect of the magnetic interchain interaction theproblem is simplified to a two-leg ladder, which is solved using density matrixrenormalization group (DMRG) calculations. We show that the deconfinement mechanismis effective even with a significantly strong antiferromagnetic interchain coupling.