Now I've written the code for Schrödinger Equation according to Chuang's paper on page 258. As you can see in my code below, the matrix SP 3n*3n is just the M matrix in the paper. The structure of my QW,GaN(4nm)/InGaN(2nm)/GaN(4nm), therefore before the if-end sentences, I just build M3*3 matrix for different cases. The problem is there will be kt in the M3n*3n matrix which doesn't have a certain value. Can I use the eigs() functrion in matlab to work out the eigenvalue as the variable with kt, i.e. the En(kt). Besides, can eigs() solve such a large matrix M300*300, or M150*150 because of symmetry.