Infrared studies of the superconducting energy gap and normal-state dynamics of the high- T sub c superconductor YBa sub 2 Cu sub 3 O sub 7

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.41.11237· OSTI ID:6815683

Schlesinger, Z; Collins, R T; Holtzberg, F; Feild, C; Koren, G; Gupta, A ^[1]

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1. IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598 (US)

A detailed study of infrared properties (reflectivity, conductivity, and dielectric response), emphasizing reproducible results from fully oxygenated YBa{sub 2}Cu{sub 3}O{sub 7} crystals ({ital T}{sub {ital c}}{congruent}93 K) and films, is presented. The extrapolated values of {sigma}{sub 1}({omega}) at low frequency are roughly consistent with the measured temperature-dependent dc resistivity. Although not well understood, this infrared conductivity can be interpreted in terms of a frequency-dependent scattering rate of {similar to}{ital kT}+{h bar}{omega}, with a low-frequency mass enhancement of roughly 2 to 4 associated with a carrier-spin related interaction. Infrared measurements polarized along the {ital c} axis suggest a conductivity anisotropy of roughly 40:1 near {ital T}{sub {ital c}} in the normal state. In the superconducting state an energy scale of 2{Delta}{sub {ital c}}{congruent}3{ital kT}{sub {ital c}} is suggested by {ital c}-axis polarized measurements, while a much larger characteristic energy of 2{Delta}{sub {ital a}-{ital b}}{congruent}8{ital kT}{sub {ital c}} is evident in the ({ital a}-{ital b})-plane conductivity. From the area missing from the conductivity up to this very large gap, a reasonable estimate ({congruent}1700 A) for the ({ital a}-{ital b})-plane penetration depth is obtained. Evidence for non-BCS temperature dependence, strong pair breaking scattering, and possible fluctuation effects is discussed. A comparison to infrared data from Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8{minus}{ital y}} shows a similarly large energy scale, 2{Delta}{sub {ital a}-{ital b}}{congruent}8{ital kT}{sub {ital c}}; for the cubic Ba{sub 0.6}K{sub 0.4}BiO{sub 3} superconductor a more conventional energy scale, 2{Delta}{congruent}4{ital kT}{sub {ital c}} is observed.

• OSTI ID: 6815683
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 41:16; ISSN PRBMD; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTALS
DIELECTRIC PROPERTIES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROMAGNETIC RADIATION
ENERGY GAP
FILMS
INFRARED RADIATION
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RADIATIONS
REFLECTIVITY
SUPERCONDUCTORS
SURFACE PROPERTIES
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES