Maisi, V. F. and Saira, O. -P. and Pashkin, Yuri and Tsai, J. S. and Averin, D. V. and Pekola, J. P. (2011) Real-time observation of discrete Andreev tunneling events. Physical review letters, 106 (21): 217003. -. ISSN 0031-9007
Abstract
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.