Rapidly oscillating ac-driven long Josephson junctions with phase-shifts

A long Josephson junction containing regions with phase shifts driven by a rapidly-oscillating ac-drive is considered. An average equation, based on multiple time scale analysis is derived, which is effectively a double sine-Gordon equation. In the presence of internal phase-shifts, it is analytically shown through the average equation that the ac-drive can influence the type of the ground state. In particular, the cases of 0 − κ and 0 − π − 0 junctions are considered. For the 0 − κ junction it is shown that an external ac-drive can reduce the critical bias current above which the junction switches to the resistive state. As for the 0 − π − 0 junction an ac-drive is shown to increase the critical length above which the ground state is nonuniform. Numerical comparisons are performed, and good agreement is obtained.