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Specific heat of the 38-K superconductor MgB2 in the normal and superconducting state: bulk evidence for a double gap

Alain Junod, Yuxing Wang, Frederic Bouquet, Pierre Toulemonde

cond-mat.supr-conarXiv:cond-mat/0106394

Abstract

The specific heat of two polycrystalline samples of MgB2 is presented and analyzed (2 - 300 K, 0 - 16 T), together with magnetic properties. The main characteristics are a low density of states at the Fermi level, high phonon frequencies, and an anomalous temperature- and field- dependence of the specific heat at T < Tc. A two-gap model with a gap ratio of 3:1 fits the specific heat in zero field. The smaller gap is washed out by a field of 0.5 T.

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