Why macroscopic quantum tunnelling in Josephson junctions differs from tunnelling of a quantum particleA. O. Sboychakov1, 2, Sergey Savel'ev1, 3, A. L. Rakhmanov1, 2, 3 and Franco Nori1, 4
1 Frontier Research System, The Institute of Physical and Chemical Research (RIKEN) - Wako-shi, Saitama, 351-0198, Japan
2 Institute for Theoretical and Applied Electrodynamics Russian Academy of Sciences - 125412 Moscow, Russia
3 Department of Physics, Loughborough University - Loughborough LE11 3TU, UK
4 MCTP, CSCS, Department of Physics, University of Michigan - Ann Arbor, MI 48109-1040, USA
received 14 June 2007; accepted in final form 17 August 2007; published October 2007
published online 17 September 2007
We show that the macroscopic quantum tunnelling of a fluxon in a Josephson junction cannot be described, even qualitatively, as the tunnelling of a quantum particle in a potential , where the phase difference plays the role of particle position, if the length of the junction d exceeds a fluxon length. We calculate the probability per unit time of tunnelling (or escape rate), , which has a form = A exp (-B). In contrast to particles, where the B is proportional to d, our field-theory predicts a different behavior of B for either usual, 0-, or stacks of Josephson junctions, giving rise to a renormalization of by many orders of magnitude.
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects.
© Europhysics Letters Association 2007