Fundamental characteristics of three-terminal thin-film microbridges

Current-voltage characteristics of a new type of superconducting weak link are investigated in which three bulk superconductors are coupled via a common weak-order-parameter region, in contrast to the usual weak links, where the coupling is limited to two superconductors. The indium three-terminal weak links studied in this experiment were made by using an electron beam lithography technique. The weak link length is typically shorter than the Ginzburg-Landau coherence length at the bath temperature, allowing strong interactions between phase-slip centers to occur inside the weak link. Pronounced structure in the I-V curves can be understood in terms of quasiparticle-exchange interactions between the phase-slip centers and order parameter variation due to current depairing. An aluminum three-terminal weak link was also investigated, showing behavior somewhat different from that of the indium weak links.