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Josephson effect in MgB_2 break junctions

R. S. Gonnelli·A. Calzolari·D. Daghero·G. A. Ummarino·V. A. Stepanov·G. Giunchi·S. Ceresara·G. Ripamonti
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Abstract

We present the first observation of the DC and AC Josephson effect in MgB_2 break junctions. The junctions, obtained at 4.2 K in high-quality, high-density polycrystalline metallic MgB_2 samples, show a non-hysteretic DC Josephson effect. By irradiating the junctions with microwaves we observe clear Shapiro steps spaced by the ideal $ΔV$ value. The temperature dependence of the DC Josephson current and the dependence of the height of the steps on the microwave power are obtained. These results are a direct prove for the existence of pairs with charge 2e in this new metallic superconductor and give evidence of the superconductor-normal metal-superconductor weak link character of these junctions.

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R. S. Gonnelli, A. Calzolari, D. Daghero, G. A. Ummarino, V. A. Stepanov, G. Giunchi, S. Ceresara, G. Ripamonti. 2001-05-11. Josephson effect in MgB_2 break junctions. https://doi.org/10.1103/physrevlett.87.097001

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