The core idea behind the k·p method is to expand the electronic wavefunctions and energies around a high-symmetry point in the Brillouin zone, typically the Γ-point. This expansion involves a perturbative approach where the Hamiltonian is written as:
H(k) = H(0) + (ħk/m)·p + ...
Here, \(H(0)\) is the Hamiltonian at the high-symmetry point, \(k\) is the wavevector, \(ħ\) is the reduced Planck constant, and \(p\) is the momentum operator. By solving this perturbed Hamiltonian, one can obtain the energy bands and eigenstates near the high-symmetry point.
