The central bond [sup 13]C=[sup 13]C isotope effect for superconductivity in high-[Tc] [beta]*-(ET)[sub 2]I[sub 3] and its implications regarding the superconducting pairing mechanism

Journal Article · Wed Dec 02 04:00:00 EST 1992 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00051a054· OSTI ID:6444417

Carlson, K D; Williams, J M; Geiser, U; Kini, A M; Wang, H H; Klemm, R A; Kumar, S K; Schlueter, J A; Ferraro, J R; Lykke, K R; Wurz, P; Sutin, J D.B. ^[1]; Parker, D H ^[2]; Schirber, J E; Venturini, E L ^[3]; Stout, P ^[4]

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1. Argonne National Lab., IL (United States)
2. Argonne National Lab., IL (United States) Univ. of California, Irvine (United States)
3. Sandia National Laboratories, Albuquerque, NM (United States)
4. Bio-Rad, Cambridge, MA (United States)

The authors report a new study, based on dc magnetization measurements, of the superconducting isotope effect for [sup 13]C-substitution in the central C=C atoms of ET [bis(ethylenedithio)tetrathiafulvalene] in [beta]*-(ET)[sub 2]I[sub 3] [or [beta][sub H]-(ET)[sub 2]I[sub 3]], the crystallographically ordered form of [beta]-(ET)[sub 2]I[sub 3] produced by pressure. The large shift reported by Merzhanov et al., [Delta][Tc] = -0.6 K, if correct, would clearly indicate that the central C=C stretching motion in the TTF moiety is a dominant exchange mechanism for superconducting pairing, because the BCS isotope effect for acoustic vibrations of the ET molecule as a whole predicts a shift, [Delta][Tc] = [Tc][sup 12]C[(386/384)[sup [minus]1/2]-1] = -0.02 K, where [Tc]([sup 12]C) refers to the salt with natural isotopes. In contrast, our study shows the absence of an isotope effect within [+-]0.1 K, indicating that the C=C stretching motion of ET is not a dominant exchange mechanism. These results are consistent with those of our very recent study of the same [sup 13]C isotope effect for the highest [Tc] ambient pressure organic superconductors, viz., [kappa]-(ET)[sub 2]Cu[N-(CN)[sub 2]]Br and [kappa]-(ET)[sub 2]Cu(NCS)[sub 2]. 22 refs., 1 fig.

• DOE Contract Number: W-31109-ENG-38; AC04-76DP00789
• OSTI ID: 6444417
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 114:25; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360607* -- Other Materials-- Superconducting Properties-- (1992-)
CARBON 13
CARBON ISOTOPES
CHEMICAL PREPARATION
EVEN-ODD NUCLEI
HIGH-TC SUPERCONDUCTORS
ISOTOPE EFFECTS
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
MAGNETIZATION
NUCLEI
ORGANIC SUPERCONDUCTORS
STABLE ISOTOPES
SUPERCONDUCTORS
SYNTHESIS