arXiv subjects

A. J. S. Machado

Publications and source records attributed to A. J. S. Machado.

21 records · Page 2Linked to original sources

arXiv2006

Observation of double superconducting transition in Y0.55Pr0.45Ba2Cu3O7-d polycrystalline sample by Hall effect measurement

This work reports longitudinal (RXX) and transverse (RXY) resistance as a function of the temperature measured at low magnetic fields for a Y0.55Pr0.45Ba2Cu3O7-d polycrystalline sample. It is observed nonzero transverse voltage at zero external magnetic below superconducting transition and above no such voltage was detected. Comparing RXX (T) and RXY (T) curves it was possible to observe a correlation between Hall resistance and double resistive superconducting transition. Magneto-resistance RXX(H) measurements showed that the dissipation is dominated by weak coupling between superconducting clusters. I-V and R(T) curves of both components suggest that the positive Hall voltage at superconducting state must be related to quasiparticle currents.

cond-mat.supr-con↗

arXiv2006

Two-Fluid Model for Granular Superconductors

A two-fluid model is proposed to describe the transport properties of granular superconductors. Using the resistively shunted junction model and some aspects of the two-level system theory, a statistical model is developed which takes into account the ratio between the number of normal and superconducting electrons carrying the applied current. The theoretical model reveals excellent agreement when compared to transport properties of four high-Tc superconductors. The results suggest that the two-fluid model is independent of the sample composition, critical temperature and whether the superconducting compound is electron or hole-doped.

cond-mat.supr-con↗

arXiv2001

Current-Induced Superconductor-Insulator Transition in Granular High-T_c Superconductors

In this work we report a systematic study of electrical current effects on superconducting properties of granular Y$_{1-x}$Pr$_{x}$Ba$_{2}$Cu$_{3}$O$_{7-δ}$ samples with x close to the critical Pr concentration above which the superconductivity vanishes. The results indicate the occurrence of superconductor-insulator quantum phase transition (SIT) driven by the applied electrical current, and suggest that the current-induced SIT can be considered as the dynamical counterpart of the magnetic-field- tuned SIT.

cond-mat.supr-con↗