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Order parameter of MgB_2: a fully gapped superconductor

H. D. Yang·J. -Y. Lin·H. H. Li·F. H. Hsu·C. J. Liu·S. -C. Li·R. -C. Yu·C. -Q. Jin
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Abstract

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 Tc of MgB_2. Together with the small specific heat jump DeltaC/gamma_nTc=1.13, scenarios like anisotropic s-wave or multi-component order parameter are called for. The magnetic field dependence of gamma(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 gamma(H) is associated with the intrinsic electronic properties other than flux pinning.

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H. D. Yang, J. -Y. Lin, H. H. Li, F. H. Hsu, C. J. Liu, S. -C. Li, R. -C. Yu, C. -Q. Jin. 2001-09-21. Order parameter of MgB_2: a fully gapped superconductor. https://doi.org/10.1103/physrevlett.87.167003

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