2006/08/31 by D. Daghero, D. Delaude, Arrigo Calzolari +12
Materials Science · Physics and Astronomy · #MXene and MAX Phase Materials #Magnesium Alloys: Properties and Applications #Superconductivity in MgB2 and Alloys #cond-mat.mtrl-sci #cond-mat.supr-con
paper · pdf · doi:10.1088/0953-8984/20/8/085225
published as J. Phys.: Condens. Matter 20 (2008) 085225 · 22 pages, 9 eps figures, Elsevier style. Theoretical details added in appendix. Characterization of crystals included
openalex publication_date 2008/02/07 · arxiv created 2008/02/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30
We present new results of point-contact Andreev-reflection (PCAR) spectroscopy in single-phase Mg 1− x Al x B 2 single crystals with x up to 0.32. Fitting the conductance curves of our point contacts with the two-band Blonder–Tinkham–Klapwijk model allowed us to extract the gap amplitudes Δ σ and Δ π . The gap values agree rather well with other PCAR results for Al-doped crystals and polycrystals up to x = 0.2 reported in the literature, and extend them to higher Al contents. In the low-doping regime, however, we observed an increase in the small gap Δ π on increasing x (or decreasing the local critical temperature of the junctions, T c A ) which is not as clearly found for other samples. On further decreasing T c A below 30 K, both the gaps decrease and, up to the highest doping level x = 0.32 and down to T c A = 12 K, no gap merging is observed. A detailed analysis of the data within the two-band Eliashberg theory shows that this gap trend can be explained as being mainly due to the band filling and to an increase in the interband scattering which is necessary to account for the increase in Δ π at low Al contents ( x <0.1). We suggest interpreting the following decrease of Δ π for T c A <30 K as being governed by the onset of the inhomogeneity and disorder in the Al distribution that partly mask the intrinsic effects of doping and are not taken into account in standard theoretical approaches.