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Magneto-optical reflectivity of superconducting MgB2 single crystals

A. Perucchi·L. Degiorgi·J. Jun·M. Angst·J. Karpinski
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Abstract

We present magneto-optical reflectivity results in the basal-plane of the hexagonal $MgB_2$. The data were collected on a mosaic of $MgB_2$ single crystals with $T_{c}=38 ~K$ from the ultraviolet down to the far infrared as a function of temperature and magnetic field oriented along the c-axis. In the far infrared there is a clear signature of the superconducting gap with a gap-ratio $2Δ/k_{B}T_{c}\sim 1.2$, well below the weak-coupling value. The gap is suppressed in an external magnetic field, which is a function of temperature. We extract the upper critical field $H_{c2}$ along the c-axis. The temperature dependence of $H_{c2}$ is compatible with the Helfand-Werthamer behaviour.

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A. Perucchi, L. Degiorgi, J. Jun, M. Angst, J. Karpinski. 2002-05-28. Magneto-optical reflectivity of superconducting MgB2 single crystals. https://doi.org/10.1103/physrevlett.89.097001

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