Tunnelling evidence for predominantly electron-phonon coupling in superconducting Ba[sub 1 [minus] x]K[sub x]BiO[sub 3] and Nd[sub 2 [minus] x]Ce[sub x]CuO[sub 4 [minus] y]

Journal Article · Thu Sep 27 04:00:00 EDT 1990 · Nature (Paris); (France)

OSTI ID:7165548

Huang, Q; Gray, K E; Hinks, D G ^[1]; Zasadzinski, J F; Tralshawala, N ^[2]; Peng, J L; Greene, R L ^[3]

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1. Argonne National laboratory, IL (United States)
2. Illinois Inst. of Technology, Chicago (United States)
3. Univ. of Maryland, College Park (United States)

Among the superconducting oxides, the cubic, copper-free Ba[sub 1 [minus]]K[sub x]BiO[sub 3] (BKBO) and the electron-doped compound Nd[sub 2 [minus] x]Ce[sub x]CuO[sub 4 [minus] y] (NCCO) stand out as being somewhat different from the rest. Nevertheless, an understanding of the pairing mechanism in BKBO (transition temperature, T[sub c] [approx] 23 K) may give important insights into the mechanisms of the higher-T[sub c] superconductors. Here the authors report tunnelling spectroscopy measurements on BKBO and NCCO. Reasonably symmetric and reproducible structures are observed in the high bias tunnelling conductances which are characteristic of phonon effects as seen in conventional superconductors. They have inverted the tunnelling data and obtained the Eliashberg functions, [alpha][sup 2]F([omega]), where F([omega]) is the phonon density of states at energy [Dirac h][omega]. For BKBO, [alpha][sup 2]F([omega]) bears a close resemblance to the available phonon density of state determined by inelastic neutron scattering, most importantly consistently reproducing the minima. The fact that the [alpha][sup 2]F([omega]) are not identical for different junctions leads to come uncertainty, but the calculated values of T[sub c] are in good agreement with experiment for both BKBO and NCCO. Also, there is a good match between the calculated values of the total electron-phonon coupling constant [lambda] and the measured 2[Delta]/at[sub c], consistent with predominantly phonon-mediated pairing mechanisms in these compounds.

• OSTI ID: 7165548
• Journal Information: Nature (Paris); (France), Journal Name: Nature (Paris); (France) Vol. 347:6291; ISSN 0369-3392; ISSN NATRAJ
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
COUPLING
DATA
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON-PHONON COUPLING
EXPERIMENTAL DATA
HIGH-TC SUPERCONDUCTORS
INFORMATION
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
RARE EARTH COMPOUNDS
SPECTROSCOPY
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
TRANSITION TEMPERATURE
TUNNEL EFFECT