Sr14Cu24O41: a complete model for the chain sub-system
Tóm tắt
A second neighbor t-J+V model for the chain subsystem of
the Sr14Cu24O41 was extracted from ab-initio
calculations. This model does not use periodic approximation but
describes the entire chain through the use of the four-dimensional
crystallographic description. Second neighbors interactions are found
to be of same order than the first neighbors ones. The computed values
of the second neighbors magnetic interactions are coherent with
experimental estimations of the intra-dimer magnetic interactions,
even if slightly smaller. The reasons of this underestimation are
detailed. The computed model allowed us to understand the origin of
the chain dimerisation and predicts correctly the relative occurrence
of dimers and free spins. The orbitals respectively supporting the
magnetic electrons and the holes have been found to be essentially
supported by the copper 3d orbitals (spins) and the surrounding
oxygen 2p orbitals (holes), thus giving a strong footing to the
existence of Zhang-Rice singlets.