Work at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Divisions of Chemistry and Materials Sciences, under Contract No. W-31-109-ENG-38. Work at Portland State University was supported by NSF (Grant No. Che-9632815) and the Petroleum Research Fund (ACS-PRF Grant No. 31099-AC1).
Physical Review B
Organic superconductors, Specific heat -- Measurement, Magnetization
We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. The jump of the specific heat C at Tc and the exact form of the specific heat difference between C in the superconducting (B=0 T) and in the normal (B=3.5 T) state can be well described by BCS theory with strong coupling. We estimate an electron-phonon coupling parameter λ≈1.1. From measurements of C in magnetic fields we extract the upper critical field Bc₂(T). Low-field dc-magnetization measurements were used to determine the temperature dependence of the lower critical field Bc₁. From Tc down to ~3 K the characteristic suppression of Bc1(T) below the sensitivity limit is observed.
Gard, Gary, Wanka, S., Hagel, J., Beckmann, D., Wosnitza, J., Schlueter, J.A., Williams, J.M., Nixon, P.G., and Winter, R.W. (1998) Specific heat and critical fields of the organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3, Physical Review B, 57, 3084