Second-order susceptibility from a tight-binding Hamiltonian

Using a new formalism that modifies a tight-binding Hamiltonian to include interaction with a time-dependent electromagnetic field, we have obtained an analytical expression for the second-order susceptibility. This expression has been used to calculate the energy dependence of χ⁽²⁾(ω) for GaAs. The results are in agreement with previous calculations and with available experimental data.