The symmetric and antisymmetric superexchange interactions in spin-Peierls system

The influences of Dzyaloshinskii--Moriya (DM) interaction andKaplan--Shekhtman--Entinwohlman--Aharony (KSEA) interaction on thedimerization of a spin-Peierls system are investigated theoreticallyby using the Lanczos numerical method. The ground state of thespin-Peierls system is still dimerized phase when both of the DM andthe KSEA interactions have the same value with Heisenberginteraction. It is found that the KSEA interaction and uniform DMinteraction are always against systemic dimerization, but thestaggered DM interaction acts in favour of dimerization. Furthermore,the influences of the DM and the KSEA interactions are also studiedin terms of the ground state index rate and the energy gap index rateof the dimerized Heisenberg system. The results show that the DMinteraction makes the index rates larger, while the KSEA interactionmakes them smaller.