Polynomial SUSY in Quantum Mechanics and Second Derivative Darboux   Transformation
  We give the classification of second-order polynomial SUSY Quantum Mechanics in one and two dimensions. The particular attention is paid to the irreducible supercharges which cannot be built by repetition of ordinary Darboux transformations. In two dimensions it is found that the binomial superalgebra leads to the dynamic symmetry generated by a central charge operator. 
A.A.Andrianov, M.V.Ioffe and D.N.Nishnianidze