Absence of an energy gap in measurements of Cu-O superconductors with high-resolution electron-energy-loss spectroscopy

We report extensive measurements of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] (Bi 2:2:1:2) and YBa[sub 2]Cu[sub 3]O[sub 7] (Y 1:2:3) single crystals with high-resolution electron-energy-loss spectroscopy (HREELS). Both as-grown and oxygen-annealed Bi 2:2:1:2 samples were studied. In all cases, peaks due...

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Bibliographic Details
Published in:Physical review. B, Condensed matter Condensed matter, 1994-09, Vol.50 (9), p.6526-6529
Main Authors: Phelps, RB, Akavoor, P, Kesmodel, LL, Barr, AL, Markert, JT, Ma, J, Kelley, RJ, Onellion, M
Format: Article
Language:English
Subjects:
665411 - Basic Superconductivity Studies- (1992-)
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
COPPER COMPOUNDS
COPPER OXIDES
CRYSTALS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY GAP
ENERGY-LOSS SPECTROSCOPY
HIGH-TC SUPERCONDUCTORS
MONOCRYSTALS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
SPECTROSCOPY
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
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Summary:We report extensive measurements of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] (Bi 2:2:1:2) and YBa[sub 2]Cu[sub 3]O[sub 7] (Y 1:2:3) single crystals with high-resolution electron-energy-loss spectroscopy (HREELS). Both as-grown and oxygen-annealed Bi 2:2:1:2 samples were studied. In all cases, peaks due to surface optical phonons were observed at loss energies from 24 to 80 meV. We see no evidence for the weak feature near 60 meV which has been previously reported and attributed to the superconducting energy gap. Our results demonstrate that the optical conductivity of high-temperature superconductors deduced from HREELS, like that deduced from infrared spectroscopy, does not exhibit the gaplike structure expected for a BCS superconductor.
ISSN:0163-1829
1095-3795
DOI:10.1103/PhysRevB.50.6526