EVIDENCE FOR A DRIVING MECHANISM OF THE W(001) RECONSTRUCTION

We report the first experimental observation of a gap-opening and chan ges of the Fermi surface contours upon reconstruction of the W(001) su rface. A gap Delta greater than or equal to 0.6 eV is found to form at (X) over bar', a new surface Brillouin zone boundary along the <(Sigm a)over bar> azimuth of the reconstructed (root 2 x root 2)R45 degrees structure. The large gap and the Fermi surface contours of which the c urvatures remain essentially unaltered through reconstruction suggest that the reconstruction is driven primarily by a strong-coupling charg e density wave mechanism. (C) 1997 Elsevier Science B.V.