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Published online by Cambridge University Press: 28 February 2011
One potential objection to virtual “sandwich excitons” as a pairing mechanism is that the transition densities may not be large enough to overcome the inherent disadvantage of a large energy denominator . In model calculations, we find that some of the transition densities and matrix elements can be large even if the dielectric constant is sizeable for, e.g., LaO excitons in La2‐xSrxCuO4