Order parameter of MgB2: A fully gapped superconductor

H. D. Yang*, Jiunn-Yuan Lin, H. H. Li, F. H. Hsu, C. J. Liu, S. C. Li, R. C. Yu, C. Q. Jin

*Corresponding author for this work

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We have measured the low-temperature specific heat C(T) for polycrystalline MgB 2 prepared by high pressure synthesis. C(T) below 10 K vanishes exponentially, which unambiguously indicates a fully opened superconducting energy gap. However, this gap is found to be too small to account for T c of MgB 2 . Together with the small specific heat jump ΔC/γ n T c = 1.09, scenarios such as anisotropic s-wave or multicomponent order parameter are called for. The magnetic field dependence of γ(H) is neither linear for a fully gapped s-wave superconductor nor H 1/2 for nodal order parameter. It seems that this intriguing behavior of γ(H) is associated with the intrinsic electronic properties other than flux pinning.

Original languageEnglish
Article number167003
JournalPhysical Review Letters
Issue number16
StatePublished - 15 Oct 2001


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