Influence of coupling between junctions on breakpoint current in intrinsic Josephson junctions

We study theoretically the current-voltage characteristics of intrinsic Josephson junctions in high-$T_c$ superconductors. An oscillation of the breakpoint current on the outermost branch as a function of coupling $\alpha$ and dissipation $\beta$ parameters is found. We explain this oscillation as a result of the creation of longitudinal plasma waves at the breakpoint with different wave numbers. We demonstrate the commensurability effect and predict a group behavior of the current-voltage characteristics for the stacks with a different number of junctions. A method to determine the wave number of longitudinal plasma waves from $\alpha$- and $\beta$-dependence of the breakpoint current is suggested. We model the $\alpha$- and $\beta$-dependence of the breakpoint current and obtain good agreement with the results of simulation.