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Temperature Evolution of the Pseudogap State in the Infra-Red Response of Underdoped La_(2-x)Sr_xCuO_4

T. Startseva·T. Timusk·A. V. Puchkov·D. N. Basov·H. A. Mook·M. Okuya·T. Kimura·K. Kishio
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Abstract

The ab-plane optical spectra of two single crystals of underdoped La_(2-x)Sr_xCuO_4 were investigated. The reflectivity of La_(1.87)Sr_(0.13)CuO_4 has been measured in the frequency range 30- 9,000 cm-1 (0.004 -- 1 eV) both parallel and perpendicular to the CuO_2 planes, whereas La_(1.86)Sr_(0.14)CuO_4 was studied only in the ab-plane. The extended Drude model shows that the frequency-dependent effective scattering rate 1/tau(omega)is strongly suppressed below the high-frequency straight-line extrapolation, a signature of the pseudogap state. This suppression can be seen from temperatures below the superconducting transition up to 400 K. In the case of underdoped LSCO the straight-line extrapolation is temperature independent below 200 K, whereas above 200 K there is a strong temperature dependence of the high-frequency 1/tau(omega,T). The out-of-plane direction is also examined for evidence of the pseudogap state.

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T. Startseva, T. Timusk, A. V. Puchkov, D. N. Basov, H. A. Mook, M. Okuya, T. Kimura, K. Kishio. 1998-12-09. Temperature Evolution of the Pseudogap State in the Infra-Red Response of Underdoped La_(2-x)Sr_xCuO_4. https://doi.org/10.1103/physrevb.59.7184

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