New Universality class for step bunching in the "C⁺-C^-" model

We formulate a new (1 + 1)D step model of unstable vicinal growth. The basic assumption is that the equilibrium adatom concentrations on both sides of the step are different. We deduce equations of step motion and numerically integrate them to obtain the step positions on a discrete time set. New dynamic phenomena are observed during the bunching process. The size-scaling of the minimal interestep distance l_minfor first time is obtained as l_min∼ N^-1/(n+1), where N is the number of steps in the bunch and n is the exponent in the step-step repulsions law U ∼ 1/dⁿfor two steps placed a distance d apart.