Optical spectra of La sub 2 minus x Sr sub x CuO sub 4 : Effect of carrier doping on the electronic structure of the CuO sub 2 plane

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.7942· OSTI ID:5562096

Uchida, S ^[1]; Ido, T; Takagi, H ^[2]; Arima, T; Tokura, Y ^[3]; Tajima, S ^[4]

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1. Engineering Research Institute, University of Tokyo, Yayoi, Tokyo 113, Japan (JP)
2. Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113, (Japan)
3. Department of Physics, University of Tokyo, Hongo, Tokyo 113, (Japan)
4. Superconducting Research Laboratory, International Superconductivity Technology Center, Shinonome, Tokyo, (Japan)

Optical reflectivity spectra are studied for single crystals of the prototypical high-{ital T}{sub {ital c}} system La{sub 2{minus}{ital x}}Sr{sub {ital x}}CuO{sub 4} over a wide compositional range 0{le}{ital x}{le}0.34, which covers insulating, superconducting, and normal metallic phases. The measurements are made at room temperature over an energy range from 0.004 to 35 eV for the polarization parallel to the CuO{sub 2} planes. They are also extended to the perpendicular polarization to study anisotropy and to discriminate the contribution from the CuO{sub 2} plane. The present study focuses on the {ital x} dependence of the optical spectrum, which makes it possible to sort out the features of the excitations in the CuO{sub 2} plane and thus to characterize the electronic structure of the CuO{sub 2} plane in the respective phase. Upon doping into the parent insulator La{sub 2}CuO{sub 4} with a charge-transfer energy gap of about 2 eV the spectral weight is rapidly transferred from the charge-transfer excitation to low-energy excitations below 1.5 eV. The low-energy spectrum is apparently composed of two contributions; a Drude-type one peaked at {omega}=0 and a broad continuum centered in the midinfrared range. The high-{ital T}{sub {ital c}} superconductivity is realized as doping proceeds and when the transfer of the spectrum weight is saturated. The resulting spectrum in the high-{ital T}{sub {ital c}} regime is suggestive of a strongly itinerant character of the state in the moderately doped CuO{sub 2} plane while appreciable weight remains in the charge-transfer energy region. The spectrum exhibits a second drastic change for heavy doping ({ital x}{similar to}0.25) corresponding to the superconductor-to-normal-metal transition and becomes close to that of a Fermi liquid.

• OSTI ID: 5562096
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:10; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTALS
DOPED MATERIALS
ELECTRICAL EQUIPMENT
ELECTRICAL INSULATORS
ELECTRONIC STRUCTURE
ENERGY GAP
EQUIPMENT
HIGH-TC SUPERCONDUCTORS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
MATERIALS
MEDIUM TEMPERATURE
OPTICAL REFLECTION
OXIDES
OXYGEN COMPOUNDS
RARE EARTH COMPOUNDS
REFLECTION
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS