Dimerization process and elementary excitations in spin-Peierls chains coupled by frustrated interactions

TL;DR

This paper investigates how frustrated and non-frustrated interchain couplings affect dimerization and elementary excitations in spin-Peierls chains, revealing that frustration can lead to deconfined solitons even with strong magnetic interactions.

Contribution

It demonstrates that frustration in interchain interactions stabilizes dimerization amplitude and allows free solitons as elementary excitations, using DMRG calculations on a simplified ladder model.

Findings

Frustration prevents dimerization amplitude from decreasing with magnetic coupling.

Free solitons can exist as elementary excitations in frustrated chains.

Deconfinement persists even with strong antiferromagnetic interchain coupling.

Abstract

We consider the ground state and the elementary excitations of an array of spin-Peierls chains coupled by elastic and magnetic interactions. It is expected that the effect of the magnetic interchain coupling will be to reduce the dimerization amplitude and that of the elastic coupling will be to confine the spin one-half solitons corresponding to each isolated chain. We show that this is the case when these interactions are not frustrated. On the other hand, in the frustrated case we show that the amplitude of dimerization in the ground state is independent of the strength of the interchain magnetic interaction in a broad range of values of this parameter. We also show that free solitons could be the elementary excitations when only nearest neighbor interactions are considered. The case of an elastic interchain coupling is analyzed on a general energetic consideration. To study the effect of the magnetic interchain interaction the problem is simplified to a two-leg ladder which is solved using DMRG calculations. We show that the deconfinement mechanism is effective even with a significantly strong antiferromagnetic interchain coupling.