Geometrical enhancement of the proximity effect in quantum wires with extended superconducting tunnel contacts

摘要: We study Andreev reflection in a ballistic one- dimensional channel coupled parallel to superconductor via tunnel barrier of finite length {\it L}. The dependence the low-energy probability R$_{A}$} on L} reveals existence characteristic scale $\xi$;$_{N}$} beyond which R$_{A}$(L)} is enhanced up unity despite low interfacial transparency. enhancement due strong mixing particle and hole states that builds contacts exceeding coherence $\xi$;$_{N}$}, leading small energy gap (minigap) density normal system. role geometry such hybrid discussed context experimental observation zero-bias anomalies resistance extended carbon nanotube/superconductor junctions field effect transistor setups.