Observation of Vortex Lattice Related Anomalies in Polycrystalline YBasub2/subCusub3/subOsub7-x/subNear the Superconducting Transition

摘要

The d.c. I-V characteristic of polycrystalline YBa2Cu3O7-x high temperature superconductors (HTSC) is measured near the transition temperature (Tc). The Tc was found to be 90 K with a width of 2 K. The voltage was measured at various current values and with reversing the current. A difference in voltage was found for forward and reverse current directions near Tc. The observed directionality of the I-V characteristic can be understood in terms of quantized magnetic flux by the self-field of the current and the proximity junctions in these materials. This can also be understood qualitatively as due to the d-wave superconductivity. The measured dc voltage showed increased noise near Tc which is possibly related to 1/f noise due to the motion of Abrikosov flux lines.