M. Truccato | Searcharxiv

arXiv2005

Evidence of ion diffusion at room temperature in microcrystals of the Bi2Sr2CaCu2O8+delta superconductor

We have studied Bi-2212 microcrystals aged at ambient conditions for 40 days. Combined x-ray absorption near edge structure and x-ray fluorescence measurements with micrometer space resolution show both an increase of Cu$^{+}$ with respect to Cu$^{2+}$ and an enrichment in Cu vs Bi and Sr cation content near the sample edges in the b-axis direction. A parallel study on an electrically contacted sample has indirectly detected the O loss, observing both a resistivity increase and an increase in sample thickness near the edges. We conclude that the O out-diffusion along the b-axis is accompanied by Cu cation migration in the same direction.

cond-mat.supr-con↗

arXiv2005

Evidence of a dominant Maki-Thompson process in the fluctuation conductivity of the Bi-2212 superconducting whiskers

We report the measurement of the a-axis fluctuation conductivity in zero field for Bi2Sr2CaCu2O8+x microcrystals. A good geometrical characterization and an original method for data analysis allow to determine its temperature behaviour to a high accuracy. The correct application of the complete fluctuation theory [A. A. Varlamov et al., Adv. Phys. 48, 655 (1999)], with a minor correction for the k_tilde factor, leads to the conclusion that the anomalous MT term is the most important contribution throughout the whole temperature range of interest. More traditional alternative interpretations of the experimental data are also investigated and their inconsistency is demonstrated. This implies an s-wave symmetry for the order parameter and could provide a physical mechanism for the preformed pair scenario.

cond-mat.supr-con↗