Local Tunneling Study of ThreeDimensional Order Parameter in the piband of Aldoped MgB.pdfVIP

APS/123-QED Local Tunneling Study of Three-Dimensional Order Parameter in the π-band of Al-doped MgB2 Single Crystals F. Giubileo, F. Bobba, A. Scarfato, and A.M. Cucolo CNR-INFM Laboratorio Regionale SUPERMAT e Dipartimento di Fisica ”E.R. Caianiello”, 6 Universita` degli Studi di Salerno, via Salvador Allende, 84081 Baronissi (SA), Italy. 0 0 A. Kohen and D. Roditchev 2 Institut des Nanosciences de Paris, INSP, Universite´ P. et M. Curie Paris 6, CNRS, UMR 75-88, Paris, France r p N. Zhigadlo and J. Karpinski A Solid State Physics Laboratory, ETH Zurich, CH-8093 Zurich, Switzerland 3 1 We have performed local tunneling spectroscopy on high quality Mg1−x Alx B2 single crystals by means of Variable Temperature Scanning Tunneling Spectroscopy (STS) in magnetic field up to 3 ] Tesla. Single gap conductance spectra due to c-axis tunneling were extensively measured, probing n different amplitudes of the three-dimensional ∆π as a function of Al content. Temperature and o magnetic field dependences of the conductance spectra were studied in S-I-N configuration: the c effect of the doping resulted in a monotonous reduction of the locally measured TC down to 24K for - r x=0.2. On the other hand, we have found that the gap amplitude shows a maximum value ∆π