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\textbf{Edge States:} Now we consider a special case of h-BHZ model. We break the 2D lattice into a strip, which means the lattice is still translational invariant along x-direction. However, the y-direction has finite number of atoms. We can modified the previous Hamiltonian in this way.  \begin{equation}  \textit{H(k_{x})}=\sum_{y=1}^{N}[\Delta+cos \textit{H(k)}=\sum_{y=1}^{N}[\Delta+cos  k_{x}]\sigma_z+Asink_x\sigma_x]\bigotimes |y\rangle\langle y|+ \\  \frac{1}{2}\sum_{y=1}^{N-1}(\sigma_z-iA \sigma_y)\bigotimes|y+1\rangle \langle y|+(\sigma_z+iA\sigma_y)\bigotimes|y\rangle \langle y+1|  \end{equation}