Anomalous optical absorption in the normal state of overdoped cuprates near the charge-ordering instability.
We argue that the hump observed in the optical conductivity at or below a few hundreds of cm(-1), in overdoped cuprates such as the electron-doped Nd(2-x)Ce(x)CuO(4-y) at x > or approximately equal to 0.15 and the hole-doped Bi2Sr2CuO6 and La2-xSrxCuO4, cannot be accounted for within a single-fluid description. We propose instead an interpretation based on the direct excitation of charge collective modes, which become nearly critical in the proximity to a charge-ordering instability. Their critical character entails a peculiar temperature dependence and a pseudoscaling form of the optical spectra, which agree with the experimental data.
Caprara
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INFM and SMC, Unità di Roma 1, and Dipartimento di Fisica-Università di Roma "La Sapienza," Piazzale Aldo Moro 2, I-00185 Roma, Italy.
Di Castro
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C
Fratini
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S
Grilli
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