Magneto-optical study of the superconducting gap of MgB(2) single crystals.
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 2 Delta/k(B)T(c) approximately 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 behavior.
Laboratorium für Festkörperphysik, ETH Zürich, CH-8093 Zürich, Switzerland.
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A
Perucchi
L
L
Degiorgi
J
J
Jun
M
M
Angst
J
J
Karpinski