Volume 79, Number 6, September 2007
Article Number 66002
Number of page(s) 5
Section Condensed Matter: Structural, Mechanical and Thermal Properties
Published online 08 August 2007
EPL, 79 (2007) 66002
DOI: 10.1209/0295-5075/79/66002

Quantum localized modes in capacitively coupled Josephson junctions

R. A. Pinto and S. Flach

Max-Planck-Institut für Physik komplexer Systeme - Nöthnitzer Str. 38, 01187 Dresden, Germany

received 25 May 2007; accepted in final form 25 July 2007; published September 2007
published online 8 August 2007

We consider the quantum dynamics of excitations in a system of two capacitively coupled Josephson junctions. Quantum breather states are found in the middle of the energy spectrum of the confined nonescaping states of the system. They are characterized by a strong excitation of one junction. These states perform slow tunneling motion from one junction to the other, while keeping their coherent nature. The tunneling time sensitively depends on the initial excitation energy. By using an external bias as a control parameter, the tunneling time can be varied with respect to the escape time and the experimentally limited coherence time. Thus, one can control the flow of quantum excitations between the two junctions.

63.20.Pw - Localized modes .
74.50.+r - Tunneling phenomena; point contacts, weak links, Josephson effects .
63.20.Ry - Anharmonic lattice modes .

© Europhysics Letters Association 2007