ANOMALOUS RE-ENTRANT SUPERCONDUCTIVITY IN Sr 0.4 K 0.6 BiO 3: RECOVERY OF SUPERCONDUCTIVITY WITH ELECTRIC AND MAGNETIC FIELD

Anomalous re-entrant superconducting-normal resistive transition was observed in Sr 0.4 K 0.6 BiO 3 superconductor i.e., normal – supernormal behavior as temperature is increased. Contrary to previously reported re-entrant resistive behaviors in other compounds, the re-entrant resistivity appearing at zero magnetic field in Sr 0.4 K 0.6 BiO 3 is suppressed to zero by applying an external magnetic field (H) or increasing the electrical transport current (I): an observation of a zero resistive superconducting state induced by H or I. Comparisons of the normal-state resistivity data in different samples indicate an important role that disorder in the junction barriers between superconducting grains might play on the observed re-entrant resistivity behavior. Possible physical origins of this anomalous phenomenon are discussed.