Strong light-induced negative optical pressure arising from the kinetic   energy of conduction electrons in plasmonic cavities
  We found that very strong negative optical pressure can be induced in plasmonic cavities by LC resonance. This interesting effect could be described qualitatively by a Lagrangian model which shows that the negative optical pressure is driven by the internal inductance and the kinetic energy of the conduction electrons. If the metal is replaced by perfect conductors, the optical pressure becomes much smaller and positive. 
H. Liu, Jack Ng, S. B. Wang, Z. F. Lin, Z. H. Hang, C. T. Chan, and S.   N. Zhu
physics.optics