Charge order in the incommensurate compounds Sr14-xCaxCu24O41

The present paper studies, using ab initio calculations, the influence of the incommensurate structural modulations on the low-energy physics of the Sr14-xCaxCu24O41 oxides. On-site, nearest-neighbor and next-nearest-neighbor effective parameters were computed within a t - J + V model based on the copper oxide layers. The structural modulations appear to be the key degree of freedom, responsible for the low-energy properties such as the electron localization, the formation of dimers in the x = 0 compound or the anti-ferromagnetic order in the x = 13.6 compound. (c) 2005 Elsevier B.V. All rights reserved.