Plasmons in cuprate superconductors

Journal Article · Wed Aug 01 00:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.42.1969· OSTI ID:6386796

Bozovic, I ^[1]

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1. Varian Research Center, 611 Hansen Way, Palo Alto, CA (USA)

The customary way of determining the complex dielectric constant from the measured reflectance spectra suffers from large uncertainties because of the extrapolations required for the Kramers-Kronig transformation. To avoid these, a method is introduced in which reflectance and ellipsometric data on single crystals and epitaxial films are combined. Utilizing this approach, the spectral functions of YBa{sub 2}Cu{sub 3}O{sub 7} (Y-Ba-Cu-O) and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} (Bi-Sr-Ca-Cu-O) are determined with substantially improved accuracy. This enables the unambiguous identification of optic plasmons at 1.4 eV in Y-Ba-Cu-O and at 1.1 eV in Bi-Sr-Ca-Cu-O. No other low-lying optic plasmons are detected, which likely rules out most plasmon-mediated superconductivity models. Next, the bare plasma frequency is found to be {h bar}{omega}{sub {ital p}}=3.2{plus minus}0.3 eV in Y-Ba-Cu-O and {h bar}{omega}{sub {ital p}}=2.4{plus minus}0.3 eV in Bi-Sr-Ca-Cu-O. These values support ascribing the strong infrared absorption to charge carriers which, however, are not free-electron-like, but rather show characteristic polaronic behavior. Finally, in both Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O, it is found that Im({minus}1/{epsilon})={beta}{omega}{sup 2} for small {omega}, and this law is conjectured to be universal for all layered cuprate superconductors. It is again not Drude-like; it may be compatible with the layered electron-gas model. The latter implies existence of a broad band of acoustic plasmon branches.

• OSTI ID: 6386796
• Journal Information: Physical Review, B: Condensed Matter; (USA), Vol. 42:4; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
PLASMONS
SUPERCONDUCTIVITY
BISMUTH OXIDES
CALCIUM OXIDES
COPPER OXIDES
HIGH-TC SUPERCONDUCTORS
STRONTIUM OXIDES
YTTRIUM OXIDES
CHARGE CARRIERS
DIELECTRIC PROPERTIES
ELLIPSOMETRY
EXPERIMENTAL DATA
INFRARED SPECTRA
SPECTRAL REFLECTANCE
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BISMUTH COMPOUNDS
CALCIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
DATA
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
INFORMATION
MEASURING METHODS
NUMERICAL DATA
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
QUASI PARTICLES
SPECTRA
STRONTIUM COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity