beta. -(ET)/sub 2/X organic superconductors: linear-anion control of structure and ambient-pressure superconductivity, and the first point-contact tunneling studies of. beta. -(ET)/sub 2/AuI/sub 2/ implying extremely strong coupling

Conference · Wed Jan 01 04:00:00 EST 1986

OSTI ID:5282324

Williams, J M; Schultz, A J; Wang, H H; Carlson, K D; Beno, M A; Emge, T J; Geiser, U; Hawley, M E; Gray, K E; Venturini, E L

Three ambient-pressure organic superconductors have been reported for linear-anion-containing 20 metallic ..beta..-(ET)/sub 2/X systems: X = I/sub 3//sup -/ (T/sub c/'s approx. = 1.5 K and 8 K under > 0.6 kbar pressure), IBr/sub 2//sup -/ (T/sub c/ approx. = 2.8 K), and AuI/sub 2//sup -/ (T/sub c/ approx. = 5 K). These systems form the basis for structure-property correlations because the T/sub c/'s scale with unit cell volume, which increases with increasing anion length. When the linear anion length becomes approximately 14 to 20% shorter than that of the longest member, I/sub 3//sup -/, as is the case for ICI/sub 2//sup -/ and AuCl/sub 2//sup -/, the electrical properties become those of a 1D metallic system in which spin-density-wave insulating ground states dominate at low temperature. In the case of the highest ambient-pressure T/sub c/ material, X = AuI/sub 2//sup -/, we report the first unambiguous point-contact tunneling measurements of the superconducting energy gap, ..delta.., which reveals a BCS temperature dependence but with a gap 5 times larger than the weak-coupling value, implying extremely strong coupling. 13 refs., 7 figs.

• Research Organization: Argonne National Lab., IL (USA); Sandia National Labs., Albuquerque, NM (USA); North Carolina State Univ., Raleigh (USA). Dept. of Chemistry
• DOE Contract Number: AC04-76DP00789; W-31109-ENG-38
• OSTI ID: 5282324
• Report Number(s): CONF-8605146-6; ON: DE86014597
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical & Physicochemical Properties-- (-1987)
BAND THEORY
BEDT-TTF
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRONIC STRUCTURE
HETEROCYCLIC COMPOUNDS
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PHYSICAL PROPERTIES
STRUCTURE-ACTIVITY RELATIONSHIPS
SUPERCONDUCTORS
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE
TUNNEL EFFECT