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Sum rules and energy scales in BiSrCaCuO

A. F. Santander-Syro·R. P. S. M. Lobo·N. Bontemps
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Abstract

From very high accuracy reflectivity spectra, we have derived the optical conductivity and estimated the spectral weight up to various cut-off frequencies in underdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (Bi-2212). We show that, when evaluating the optical spectral weight over the full conduction band (1 eV), the kinetic energy decreases in the superconducting state, unlike in conventional BCS superconductors. As a consequence, the Ferrell-Glover-Tinkham sum rule is not satisfied up to this energy scale. This stands as a very unconventional behavior, contrasted with the overdoped Bi-2212 sample.

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A. F. Santander-Syro, R. P. S. M. Lobo, N. Bontemps. 2004-04-13. Sum rules and energy scales in BiSrCaCuO. https://arxiv.org/abs/cond-mat/0404290

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