The central bond sup 13 C double bond sup 13 C isotope effect for superconductivity in the high-T sub c. beta. *-(ET) sub 2 I sub 3 phase and its implications regarding the superconducting pairing mechanism in TTF-based organic superconductors

Conference · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7241746

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]

---

1. Argonne National Lab., IL (United States)
2. Argonne National Lab., IL (United States) California Univ., Irvine, CA (United States). Dept. of Chemistry
3. Sandia National Labs., Albuquerque, NM (United S

We report a new study, based on magnetization measurements, of the isotope effect for {sup 13}C substitution in the electronically active central double-bonded carbon atoms (C=C) of the TTF moiety of ET (bis(ethylenedithio)tetrathiafulvalene) in {beta}*-(ET){sub 2}I{sub 3} which is the crystallographically ordered form of {beta}-(ET){sub 2}I{sub 3} produced by application of pressure. A recent report by Merzhanov et al. (C. R. Acad. Sci., Paris, 314, 563 (1992)) has shown that this same {sup C} substitution leads to a giant'' isotope effect ({Delta}{Tc} = {minus} 0.6 K) in resistive determinations of {Tc} ({approximately} 8 K) for {beta}-(ET){sub 2}I{sub 3}, which lends experimental support to a theory by Yamaji (Solid State Common., 61, 413. (1987)) for salts of TTF-analogue donor molecules that includes optical phonons of symmetric intramolecular vibrations as a source of mediation for superconducting pairing of charge-carriers. In contrast to this result, our study shows the absence of an isotope effect within a precision of {plus minus} 0.1 K.({approximately} l%), indicating that the central atom C=C stretching motion ({approximately} 1500 cm{sup {minus}1}) of ET cannot be a dominant mechanism for phonon exchange. Our results are consistent with those of a very recent study of the same isotope effect for {kappa}-(ET){sub 2}Cu(N(CN){sub 2})Br and {kappa}-(ET){sub 2}Cu(NCS){sub 2} (Inorg. Chem., 32, 3356 (1992)).

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38; AC04-76DP00789
• OSTI ID: 7241746
• Report Number(s): ANL/CP-75668; CONF-920850--1; ON: DE92040725
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360607* -- Other Materials-- Superconducting Properties-- (1992-)
665411 -- Basic Superconductivity Studies-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BEDT-TTF
CARBON 13
CARBON ISOTOPES
CHEMICAL BONDS
DOUBLE BONDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
EVEN-ODD NUCLEI
HETEROCYCLIC COMPOUNDS
ISOTOPE EFFECTS
ISOTOPES
LIGHT NUCLEI
MAGNETIZATION
NUCLEI
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANIC SUPERCONDUCTORS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
STABLE ISOTOPES
SUPERCONDUCTIVITY
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE