Friday, April 12, 2013

1304.3354 (Sheng Li et al.)

Strong coupling superconductivity and prominent superconducting
fluctuations in the new superconductor Bi4O4S3
   [PDF]

Sheng Li, Huan Yang, Delong Fang, Zhenyu Wang, Jian Tao, Xiaxin Ding, Hai-Hu Wen
Electric transport and scanning tunnelling spectrum (STS) have been investigated on polycrystalline samples of the new superconductor Bi4O4S3. A weak insulating behavior in the resistive curve has been induced in the normal state when the superconductivity is suppressed by applying a magnetic field. Interestingly, a kink appears on the temperature dependence of resistivity at about 4 K at all high magnetic fields when the bulk superconductivity is completely suppressed. This kink can be well traced back to the upper critical field in the low field and high temperature region, and is explained as the possible evidence of residual Cooper pairs. A superconducting gap of about 3 meV is frequently observed yielding a ratio of 2\Delta/kBTc ~ 17. This value is much larger than the one predicted by the BCS theory in the weak coupling regime (2\Delta/kBTc ~ 3.53), which suggests the strong coupling superconductivity in the present system. Furthermore, the superconducting feature persists on the spectra until 14 K, which demonstrates a prominent fluctuation region of superconductivity. Such superconducting fluctuation can survive at very high magnetic fields when the bulk superconductivity is completely suppressed as inferred both from electric transport and tunnelling measurements. Our results provide strong evidence for unconventional superconductivity in Bi4O4S3.
View original: http://arxiv.org/abs/1304.3354

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