Bunching of fluxons by means of Cherenkov radiation in 
Josephson multilayers

E.Goldobin

KFA, Juelich, Germany.

A single magnetic fluxon moving at a high velocity in a Josephson
multilayer (e.g., high-temperature superconductor such as BSCCO) can
emit electromagnetic waves (Cherenkov radiation), which leads to
formation of novel stable dynamic states consisting of several bunched
fluxons. We find such bunched states in numerical simulation in the
simplest cases of two and three coupled junctions. At a given driving
current, several different bunched states are stable and move at
velocities that are higher than corresponding single-fluxon velocity.
These and some of the more complex higher-order bunched states and
transitions between them are investigated in detail.