Clean and Dirty Superconductivity in Pure, Al doped, and Neutron Irradiated MgB2: a Far-Infrared Study

M. Ortolani; D. Di Castro; P. Postorino; I. Pallecchi; M. Monni; M. Putti; P. Dore

doi:10.1103/PhysRevB.71.172508

paper

Clean and Dirty Superconductivity in Pure, Al doped, and Neutron Irradiated MgB2: a Far-Infrared Study

arXiv:cond-mat/0411616 · doi:10.1103/PhysRevB.71.172508

Abstract

The effects of Al substitution and neutron irradiation on the conduction regime (clean or dirty) of the $I ¨ $ - and $I ¨ $ -band of MgB $_{2}$ have been investigated by means of far-infrared spectroscopy. The intensity reflected by well characterized polycrystalline samples was measured up to 100 cm $^{- 1}$ in both normal and superconducting state. The analysis of the superconducting to normal reflectivity ratios shows that only the effect of the opening of the small gap in the dirty $I ¨ $ -band can be clearly observed in pure MgB $_{2}$ , consistently with previous results. In Al-doped samples the dirty character of the $I ¨ $ -band is increased, while no definitive conclusion on the conduction regime of the $I ¨ $ -band can be drawn. On the contrary, results obtained for the irradiated sample show that the irradiation-induced disorder drives the $I ¨ $ -band in the dirty regime, making the large gap in $I ¨ $ -band observable for the first time in far-infrared measurements.

11 pages, 1 figure