Experimental Evidence for One Highly Dispersive Dangling-Bond Band on Si(111) 2 × 1

Angle-resolved photoemission data along the $\overline{\Gamma }-\overline{J}$ symmetry line in the surface Brillouin zone of the Si(111) 2 × 1 surface show that there exists only one dangling-bond band. This fact removes the experimental basis for the introduction of electron correlation effects for the Si(111) 2 × 1 surface. The dangling-bond band shows a large positive energy dispersion, which favors the recently suggested $\pi$-bonded chain model instead of the widely considered buckling model.