Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

I am confused by the wavevector in spectral function A(k,w). How to understand this k for a periodic structure? And how is it related to the k (in first Brillouin Zone) we use in the band structure? If there are multibands, then in band structure for the same k we have several energies. To roughly reproduce spectral function, do I expect several peaks for the same k in A(k,w) or I need to unfold the multibands, and the multi energies for same k in band structure appear at different k in A(k,w)? Thanks!

share|improve this question
You should try to do the calculation for free electrons for a two-band model and see what happens (and tell us the resul !). –  Adam 2 days ago
add comment

1 Answer

The spectral function has a peak function at the energy and momentum of long-lived excitations. As with all observables in a crystal the spectral function is fully defined by the first Brillouin Zone. In the case of the spectral function corresponding to the physical electron Green's function, you would see at fixed momentum a peak at the energy for every band. This is what is measured in ARPES experiments for example.

share|improve this answer
Thanks. Then I have an another question. If we have a system with simple unit cell. In its first Brillouin Zone there is only one band. If we add to the system a potential with large periodicity, then we have a supercell, corresponding to a mini first BZ. Now band structure are folded back to mini BZ and for same k in the mini BZ we have multi bands. Are we going to observe multiple peaks at fixed momentum in ARPES? If so, it will be confusing since the perturbation potential can be infinitesimally small and ARPES results should be continuous to unperturbed case. –  jinchenhao Jun 19 '13 at 21:11
add comment

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.