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The effect of magnetic impurities in a two-band superconductor: A point-contact study of Mn-substituted MgB2 single crystals

R. S. Gonnelli·D. Daghero·G. A. Ummarino·A. Calzolari·M. Tortello·V. A. Stepanov·N. D. Zhigadlo·K. Rogacki·J. Karpinski·F. Bernardini·S. Massidda
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Abstract

We present the first results of directional point-contact measurements in Mg_{1-x}Mn_{x}B_2 single crystals, with x up to 0.015 and bulk T_c down to 13.3 K. The order parameters Delta_{sigma} and Delta_{pi} were obtained by fitting the conductance curves with the two-band Blonder-Tinkham-Klapwijk (BTK) model. Both Delta_{pi} and Delta_{sigma} decrease with the critical temperature of the junctions T_c^A, but remain clearly distinct up to the highest Mn content. Once analyzed within the Eliashberg theory, the results indicate that spin-flip scattering is dominant in the sigma band, as also confirmed by first-principle band structure calculations.

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R. S. Gonnelli, D. Daghero, G. A. Ummarino, A. Calzolari, M. Tortello, V. A. Stepanov, N. D. Zhigadlo, K. Rogacki, J. Karpinski, F. Bernardini, S. Massidda. 2006-03-10. The effect of magnetic impurities in a two-band superconductor: A point-contact study of Mn-substituted MgB2 single crystals. https://doi.org/10.1103/physrevlett.97.037001

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