The horizon of Josephson point contacts

AbstractJosephson point contacts can have rather small dynamic capacitances of order 0.1 fF and huge plasma frequenciesu1*1ps~1. The quantum-mechanical zero-point #uctuations of the Josephson plasma interact with the electromag-netic "eld only inside the horizon & c /u1of the junction, and the dynamic capacitance turns out to be C +i c /u1ataleadcapacitanceper lengthi. Thosecontactscaneasily resistexternalhigh-frequencynoise. ( 2000 ElsevierScienceB.V. All rights reserved. PACS : 74.50.#r; 74.40.#k; 74.60.Jg; 73.40.Jm Keywords: Break junctions; Horizon model; Josephson e!ect The supercurrent I 0#sin u across a Josephson junctionis always accompanied by a normal quasi-particle cur-rent,describedbyaparallelresistance R " R 21,aswellasadisplacementcurrentduetoacapacitance C ,represent-ing a short circuit for the high-frequency part of thesupercurrent.Such a resistively and capacitivelyshuntedjunction can be modelled by a particle of &mass’ (+/2 e )2 C exposed to a viscous damping force (+/2