Fractional charge excitations in fermionic ladders
  The system of interacting spinless fermions hopping on a two-leg ladder in the presence of an external magnetic field is shown to possess a long range order: the bond density wave or the staggered flux phase. In both cases the elementary excitations are $Z_2$ kinks and carry one half the charge of an electron. 
B.N. Narozhny, S.T. Carr, and A.A. Nersesyan