30 research outputs found
Abrupt rotation of the rashba spin to the direction perpendicular to the surface
金沢大学理工研究域数物科学系The polarization vector of the Rashba spin, which must be parallel to the two-dimensional (2D) plane in an ideal system, is found to change abruptly and definitely to the direction perpendicular to the surface at the K̄ point of the Brillouin zone of a real hexagonal system, the Tl/Si(111)-(1×1) surface. This finding obtained experimentally by angle-resolved and spin-resolved photoemission measurements is fully confirmed by a first-principles theoretical calculation. We found that the abrupt rotation of the Rashba spin is simply understood by the 2D symmetry of the hexagonal structure. © 2009 The American Physical Society
Electronic Structure of Te and As Covered Si(211)
Electronic and atomic structures of the clean, and As and Te covered Si(211)
surface are studied using pseudopotential density functional method. The clean
surface is found to have (2 X 1) and rebonded (1 X 1) reconstructions as stable
surface structures, but no \pi-bonded chain reconstruction. Binding energies of
As and Te adatoms at a number of symmetry sites on the ideal and (2 X 1)
reconstructed surfaces have been calculated because of their importance in the
epitaxial growth of CdTe and other materials on the Si(211) surface. The
special symmetry sites on these surfaces having the highest binding energies
for isolated As and Te adatoms are identified. But more significantly, several
sites are found to be nearly degenerate in binding energy values. This has
important consequences for epitaxial growth processes. Optimal structures
calculated for 0.5 ML of As and Te coverage reveal that the As adatoms dimerize
on the surface while the Te adatoms do not. However, both As and Te covered
surfaces are found to be metallic in nature.Comment: 17 pages, 9 figures, accepted for publication in Phys. Rev.
Te covered Si(001): a variable surface reconstruction
At a given temperature, clean and adatom covered silicon surfaces usually
exhibit well-defined reconstruction patterns. Our finite temperature ab-initio
molecular dynamics calculations show that the tellurium covered Si(001) surface
is an exception. Soft longitudinal modes of surface phonons due to the strongly
anharmonic potential of the bridged tellurium atoms prevent the reconstruction
structure from attaining any permanent, two dimensional periodic geometry. This
explains why experiments attempting to find a definite model for the
reconstruction have reached conflicting conclusions.Comment: 4 pages, 3 gif figure
Two-domains bulklike Fermi surface of Ag films deposited onto Si(111)-(7x7)
Thick metallic silver films have been deposited onto Si(111)-(7x7) substrates
at room temperature. Their electronic properties have been studied by using
angle resolved photoelectron spectroscopy (ARPES). In addition to the
electronic band dispersion along the high-symmetry directions, the Fermi
surface topology of the grown films has been investigated. Using ARPES, the
spectral weight distribution at the Fermi level throughout large portions of
the reciprocal space has been determined at particular perpendicular
electron-momentum values. Systematically, the contours of the Fermi surface of
these films reflected a sixfold symmetry instead of the threefold symmetry of
Ag single crystal. This loss of symmetry has been attributed to the fact that
these films appear to be composed by two sets of domains rotated 60 from
each other. Extra, photoemission features at the Fermi level were also
detected, which have been attributed to the presence of surface states and
\textit{sp}-quantum states. The dimensionality of the Fermi surface of these
films has been analyzed studying the dependence of the Fermi surface contours
with the incident photon energy. The behavior of these contours measured at
particular points along the Ag L high-symmetry direction puts forward
the three-dimensional character of the electronic structure of the films
investigated.Comment: 10 pages, 12 figures, submitted to Physical Review