New view of the occupied band structure of Mo(112)

Abstract

We present a comprehensive examination of the occupied surface-weighted band structure of Mo(112) along the two high-symmetry directions of the surface Brillouin zone both from theoretical and experimental perspectives. The band structures are found to be significantly different for the states along the two high-symmetry directions and for the states with even and odd reflection parities with respect to the mirror planes. The present study suggests the existence of number of surface weighted bands along both high-symmetry directions. The complexity of the band structure near the Fermi level may impose potential difficulties in experimental determination of the electron-phonon coupling parameters based on the effective mass enhancement distortion (or kink) in the energy-band dispersion, in the vicinity of the Fermi level, for several surface resonance bands of Mo(112).

Enhanced electron-phonon coupling at the Au/Mo(112) surface

“…So far, several experimental and theoretical studies of Mo [5,18,19,34] have been devoted to the characterization of the electron-phonon coupling parameters of the bulk as well as various surfaces. In particular, the mass enhancement parameter due to the electron-phonon coupling for Mo bulk was calculated to be λ = 0.39-0.42 [19,34], which may be in agreement with the possible experimental identification of λ = 0.42 for the bulk-weighted band [18,22] (some of the possible complication are detailed in [22]). The electron-phonon coupling parameters λ for Mo(110) and Mo(112) have also been reported [5,19] and are summarized in Table 1 …”

“…Such a calculation gives identical Σ (e-p) values for all the bands in the entire SBZ, whereas in general it should be different for each band. Either that the structural and electronic anisotropy of 1 ML Au/Mo(112) is not significant enough to cause major anisotropy in electron-phonon coupling (to the degree it can be readily identified in the scale of Figure 5), or the band chosen for this particular analysis "coincidentally" agrees very well with the homogeneous (or averaged) model of electron-phonon coupling, in spite of the anisotropic electronic structure [22].…”

“…The surface of the Mo(112) sample was cleaned by the standard method of repeated annealing (at ~1400°C) in oxygen atmosphere with the oxygen partial pressure of ~1×10 -6 torr, followed by cycles of annealing at 1000-1300°C and flashing at ~1800°C, similar to the procedures used elsewhere [22,[25][26][27][28][29]. Low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) were used to verify the quality of the Mo(112) surface.…”

“…This is crucial in two ways: (1) since the electron-phonon coupling parameters in bulk and in surface are generally different, the origin of the bands (that is to say the contributing weight is surface-derived, bulk-derived, or a surface resonance) should be clearly understood when the experimental results are to be compared to the ab initio calculation, (2) due to the finite resolution of ARPES, there arises, in some cases, overlap of the spectral intensities which can obscure the small renormalization of the electronic band dispersion [22].…”

“…The Mo(112) surface is known to exhibit highly anisotropic electronic structure [22] on which Au forms the commensurate atomic chains, as schematically illustrated in Figure 1a. At certain coverages of Au/Mo(112), order-disorder transitions of the Au chains have been observed [23].…”