I am studying surface states currently and am a little confused about something.
If I consider p-orbits on a surface state that is the top layer of an HCP structure -- I understand the hopping terms between p_x and p_y orbitals will be the same as the bulk. But on the surface inversion symmetry is broken due to the p_z orbital, and hopping between p_x / p_y and p_z orbitals is nonzero. In the bulk I understand the lobs will overlap in a way to just cancel any hopping effects, but on the surface this is different. I am just trying to get a feel for what this looks like. Are the p_z lobs on the surface different shape / size? Is the one extending into the bulk larger than the one on the surface, is this why p_x / p_y can now hop to p_z because the overlap does not cancel?
something like this:
So, ya, is this picture correct? If not, what exactly causes the non zero hopping term between p_x / p_y and p_z orbitals.