Optical properties of single-crystal La{sub 2}CuO{sub 4+{delta}}
- Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)
- AT&T Bell Laboratories, Murray Hill, New Jersey 07974 (United States)
The {ital c}-axis and {ital ab}-plane optical reflectance of an electrochemically oxidized single crystal of La{sub 2}CuO{sub 4+{delta}} ({ital T}{sub {ital c}}{similar_to}40 K; {delta}{similar_to}0.12) have been measured over a wide frequency range (30--40 000 cm{sup {minus}1}) and at temperatures between 10 and 300 K. The {ital ab}-plane optical conductivity shows metallic behavior at low frequency with weak phonon features whereas the {ital c}-axis spectrum is typical of an insulator, showing only phonons. Estimates of the carrier density and the oxygen concentration suggest that each excess oxygen contributes just over one mobile hole. The {ital ab}-plane midinfrared conductivity obtained when the wave vector {bold q} of the light is perpendicular to the CuO{sub 2} planes in the sample exhibits structure that is absent when {bold q} is parallel to the basal planes. The {ital ab}-plane conductivity shows a strong departure from Drude metallic response; fits to midinfrared models with frequency-dependent damping require also an additional bound-carrier contribution. A superconducting condensate is evident in the low-frequency {ital ab}-plane data; the oscillator strength of this condensate contains about 18% of the doping induced or 80% of the free carrier spectral weight in the normal state. Finally, an anomalous temperature dependence is found in the visible/ultraviolet region of the spectrum.
- Research Organization:
- Ames National Laboratory
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 132867
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 52, Issue 21; Other Information: PBD: 1 Dec 1995
- Country of Publication:
- United States
- Language:
- English
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