Evidence for single-gap superconductivity in Mg(B1−xCx)2 single crystals with x=0.132 from point-contact spectroscopy

R. S. Gonnelli; D. Daghero; A. Calzolari; G. A. Ummarino; Valeria Dellarocca; V. A. Stepanov; S. M. Kazakov; N. Zhigadlo; J. Karpinski

doi:10.1103/PhysRevB.71.060503

Evidence for single-gap superconductivity in Mg(B1−xCx)2 single crystals with x=0.132 from point-contact spectroscopy

R. S. Gonnelli, D. Daghero, A. Calzolari, G. A. Ummarino, Valeria Dellarocca, V. A. Stepanov, S. M. Kazakov, N. Zhigadlo, J. Karpinski

DOI 10.1103/PhysRevB.71.060503 · Physical Review B

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Abstract

We report the results of the first directional point-contact measurements in Mg(B1−xCx)2 single crystals with 0.047⩽x⩽0.132. The two-gap superconductivity typical of MgB2 persists up to x=0.105. In this region, the values of the gaps Δσ and Δπ were determined by fitting the Andreev-reflection conductance curves with a two-band Blonder-Tinkham-Klapwijk (BTK) model, and confirmed by the single-band BTK fit of the σ- and π-band conductances, separated by means of a magnetic field. At x=0.132, when Tc=19K, we clearly observed the merging of the two gaps into one of amplitude Δ≃3meV.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
Mg(B1-xCx)2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	19	Pressure not reported	unknown
MgB2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	39	Pressure not reported	unknown