Enhanced Superconductivity in Layers of Ga Fine Particles

抄録

In layers of Ga fine particles prepared by gas evaporation technique, the temperature dependence of dc electric resistance was measured for average diameters of 22–56 nm. The resistance versus temperature curve of a layer has two superconducting transition points near 6 K and less than 2 K. The resistance of the layer decreases first at slightly higher temperature than the bulk transition of β phase Ga and the value of resistance does not fall to zero. The second sharp transition to zero resistance occurs at higher temperature than that of α phase bulk Ga. These results suggest an enhancement of the transition temperature T_c in α and β phase Ga fine particles. The observed values of T_c for α and β phase fine particles increase with decreasing average diameter of α phase particles in the layer. The enhanced T_c can be explained by change in phonon spectrum due to the surface of fine particle.