Josephson Effect in Weak Links between URu₂Si₂ and Nb

Abstract

Josephson critical current density J_c between a single crystal URu₂Si₂ and an s-wave superconductor has been investigated for URu₂Si₂–Cu–Nb(SNS′) and URu₂Si₂–Nb(SS′) junctions. In contrast to the previous result for point-contacts, J_c is observed along the c-axis as well as the a-axis direction of URu₂Si₂. The J_c value in SS′ junctions is of the same order of magnitude independent of current direction or surface roughness of the (001) plane, suggesting that c-axis Josephson coupling is intrinsic.