We provide a direct proof of two-electron Andreev transitions in a superconductor–normal-metal tunnel junction by detecting them in a real-time electron counting experiment. Our results are consistent with ballistic Andreev transport with an order of magnitude higher rate than expected for a uniform barrier, suggesting that only part of the interface is effectively contributing to the transport. These findings are quantitatively supported by our direct current measurements in single-electron transistors with similar tunnel barriers.
|Number of pages||4|
|Journal||Physical Review Letters|
|Publication status||Published - 2011|
|MoE publication type||A1 Journal article-refereed|