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Theory of Excitons in Insulating Cu-Oxide Plane

Fu Chun Zhang·Kwai-Kong Ng
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Abstract

We use a local model to study the formation and the structure of the low energy charge transfer excitations in the insulating Cu-O$_2$ 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 Sr$_2$CuO$_2$Cl$_2$.

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Fu Chun Zhang, Kwai-Kong Ng. 1998-04-06. Theory of Excitons in Insulating Cu-Oxide Plane. https://arxiv.org/abs/cond-mat/9804072

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