Electronic factors leading to Peierls and spin-Peierls distortions: Effects of pairing-distortion on the electronic properties of the metallic and the insulating states of a half-filled band

Abstract

A common theoretical link between Peierls and spin-Peierls distortions was explored in the present work by studying the effects of pairing-distortion on the electronic properties of the metallic and insulating states of a half-filled band. It is possible to discuss the cause for a spin-Peierls distortion in terms of the electronic energy as in the case of a Peierls distortion if the ground electronic state of a Heisenberg antiferromagnetic chain is approximated by the Slater antiferromagnetic state of a very narrow band. The present work suggests that a spin-Peierls distortion can be regarded to originate from a bond density wave developed on top of an antiferromagnetic state, just as a Peierls distortion can be considered to result from a bond density wave created on top of a metallic state. Formation of a bond density wave in a regular chain is found to be independent of the on-site repulsion but enhanced by the intersite repulsion. The potentials exerting on the two sides of each lattice site of a regular chain become inequivalent upon introducing a bond density wave, so that the leading term of the energy variation with the lattice distortion becomes linear in the lattice displacement.