Two superconducting gaps and electron-phonon coupling in YBa sub 2 Cu sub 4 O sub 8

Journal Article · Sat Jun 01 04:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.43.12958· OSTI ID:5622873

Heyen, E T; Cardona, M ^[1]; Karpinski, J; Kaldis, E; Rusiecki, S ^[2]

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1. Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-7000 Stuttgart 80, Federal Republic of Germany (DE)
2. Laboratorium fuer Festkoerperphysik, Eidgenoessische Technische Hochschule Zuerich-Hoenggerberg, 8093 Zuerich, Switzerland (CH)

We report measurements of the superconducting gaps and the electron-phonon coupling in untwinned YBa{sub 2}Cu{sub 4}O{sub 8} (Y 1:2:4) single crystals by electronic and phononic Raman scattering. For {ital xx}- and, to a lesser extent, also for {ital yy}-polarized light, a scattering continuum that decreases in the superconducting state below 325 cm{sup {minus}1} (thus signaling a gap 2{Delta}{sub 2} such that 2{Delta}{sub 2}/{ital kT}{sub {ital c}}{approx}6.5) is observed. We measure, in {ital yy} polarization only, another sharp decrease of the electronic scattering below 113 cm{sup {minus}1}, indicating a second gap 2{Delta}{sub 1}, such that 2{Delta}{sub 1}/{ital kT}{sub {ital c}}{approx}2.3. The existence and the size of both gaps are confirmed by the observation of phonon anomalies at {ital T}{sub {ital c}} for nearly all {ital A}{sub {ital g}} phonons. We conjecture that the smaller gap {Delta}{sub 1} occurs at the chain bands and probably also exists in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (Y 1:2:3) but cannot be observed by Raman scattering.

• OSTI ID: 5622873
• Journal Information: Physical Review, B: Condensed Matter; (USA), Journal Name: Physical Review, B: Condensed Matter; (USA) Vol. 43:16; 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
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTALS
ELECTRON-PHONON COUPLING
ENERGY GAP
HIGH-TC SUPERCONDUCTORS
MONOCRYSTALS
OXIDES
OXYGEN COMPOUNDS
POLARIZATION
RAMAN SPECTRA
SPECTRA
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES