Specific heat of the ambient-pressure organic superconductor β-di[bis(ethylenedithio)tetrathiafulvalene] triiodide [β-(BEDT-TTF)2I3]

Abstract

We have measured the specific heat of single crystals of the ambient-pressure superconductor β-(BEDT-TTF)2I3, abbreviated β-(ET)2I3, from 0.7 to 18 K in zero and applied magnetic fields. No bulk specific-heat anomaly in the vicinity of Tc was observed, although Meissner-effect measurements (H∥c*) performed on these same crystals yield a volume percent superconductivity of at least 25% at 0.8 K. We find a γ=24±3 mJ/mol K2, which is larger than the value for the only previously known ambient-pressure superconductor, the Se-based (TMTSF)2ClO4 (TMTSF denotes tetramethyltetraselenafulvalene). This difference is due primarily to the greater density of S atoms in β-(ET)2I3 compared to the density of Se atoms in (TMTSF)2ClO4. The response of the low-temperature specific heat to fields up to 10 T aligned along c* was 0 to ±3%, in sharp contrast to previous reports of a 20% increase in the specific heat of (TMTSF)2ClO4 in a field of 2 T. No evidence for a high-field magnetic or insulating state similar to that observed in (TMTSF)2ClO4 was found for β-(ET)2I3. New results on the specific heat in applied fields for (TMTSF)2ClO4 are presented.

Source-reported materials — not catalogue approval

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