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

Related Subjects

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