We use a local model to study the formation and the structure of the low energy charge transfer excitations in the insulating Cu-O2 plane. The elementary excitation is a bound exciton of spin singlet, consisting of a Cu+ and a neighboring spin singlet of Cu-O holes. The exciton can move through the lattice freely without disturbing the antiferromagnetic spin background, in contrast to the single hole motion. There are four eigen-modes of excitons with different symmetry. The p-wave-like exciton has a large dispersion width. The s-wave-like exciton mixes with p-state at finite momentum, and its dipole transition intensity is strongly anisotropic. The model is in excellent agreement with the electron energy loss spectra in the insulating Sr2CuO2Cl2.
@article{arxiv.cond-mat/9804072,
title = {Theory of Excitons in Insulating Cu-Oxide Plane},
author = {Fu Chun Zhang and Kwai-Kong Ng},
journal= {arXiv preprint arXiv:cond-mat/9804072},
year = {2007}
}
Comments
5 pages, 5 figures and 1 table. Submitted to Phys. Rev. B