Parametrically Driven Dark Solitons
  We show that unlike the bright solitons, the parametrically driven kinks are immune from instabilities for all dampings and forcing amplitudes; they can also form stable bound states. In the undamped case, the two types of stable kinks and their complexes can travel with nonzero velocities. 
I.V. Barashenkov, S.R. Woodford, E.V. Zemlyanaya