33,235 research outputs found
Variability of structural and electronic properties of bulk and monolayer Si2Te3
Since the emergence of monolayer graphene as a promising two-dimensional
material, many other monolayer and few-layer materials have been investigated
extensively. An experimental study of few-layer Si2Te3 was recently reported,
showing that the material has diverse properties for potential applications in
Si-based devices ranging from fully integrated thermoelectrics to
optoelectronics to chemical sensors. This material has a unique layered
structure: it has a hexagonal closed-packed Te sublattice, with Si dimers
occupying octahedral intercalation sites. Here we report a theoretical study of
this material in both bulk and monolayer form, unveiling a fascinating array of
diverse properties arising from reorientations of the silicon dimers between
planes of Te atoms. The lattice constant varies up to 5% and the band gap
varies up to 40% depending on dimer orientations. The monolayer band gap is 0.4
eV larger than the bulk-phase value for the lowest-energy configuration of Si
dimers. These properties are, in principle, controllable by temperature and
strain, making Si2T3 a promising candidate material for nanoscale mechanical,
optical, and memristive devices.Comment: 9 pages, 4 figure
Low-Energy Electronic Structure of the High-Tc Cuprates La2-xSrxCuO4 Studied by Angle-resolved Photoemission Spectroscopy
We have performed a systematic angle-resolved photoemission spectroscopy
(ARPES) study of the high-Tc cuprates La2-xSrxCuO4, ranging from the underdoped
insulator to the superconductor to the overdoped metal. We have revealed a
systematic doping evolution of the band dispersions and (underlying) Fermi
surfaces, pseudogap and quasi-particle features under the influence of strong
electron-electron interaction and electron-phonon interaction. The unusual
transport and thermodynamic properties are explained by taking into account the
pseudogap opening and the Fermi arc formation, due to which the carrier number
decreases as the doped hole concentration decreases.Comment: 27 pages, 17 figures, accepted in Journal of Physics Condensed Matte
Underlying Fermi surface of SrCaCuO in two-dimensional momentum space observed by angle-resolved photoemission spectroscopy
We have performed an angle-resolved photoemission study of the two-leg ladder
system SrCaCuO with = 0 and 11. "Underlying Fermi
surfaces" determined from low energy spectral weight mapping indicates the
quasi-one dimensional nature of the electronic structure. Energy gap caused by
the charge density wave has been observed for =0 and the gap tends to close
with Ca substitution. The absence of a quasi-particle peak even in =11 is in
contrast to the two-dimensional high- cuprates, implying strong carrier
localization related to the hole crystalization.Comment: 5 pages, 3 figure
Interaction between graphene and SiO2 surface
With first-principles DFT calculations, the interaction between graphene and
SiO2 surface has been analyzed by constructing the different configurations
based on {\alpha}-quartz and cristobalite structures. The single layer graphene
can stay stably on SiO2 surface is explained based on the general consideration
of configuration structures of SiO2 surface. It is also found that the oxygen
defect in SiO2 surface can shift the Fermi level of graphene down which opens
out the mechanism of hole-doping effect of graphene absorbed on SiO2 surface
observed in experiments.Comment: 17 pages, 7 figure
Polaronic behavior of undoped high-Tc cuprates
We present angle-resolved photoemission spectroscopy (ARPES) data on undoped
La2CuO4, indicating polaronic coupling between bosons and charge carriers.
Using a shell model, we calculate the electron-phonon coupling and find that it
is strong enough to give polarons. We develop an efficient method for
calculating ARPES spectra in undoped systems. Using the calculated couplings,
we find the width of the phonon side band in good agreement with experiment. We
analyze reasons for the observed dependence of the width on the binding energy.Comment: 4 pages, RevTeX, 5 eps figures, more material available at
http://www.fkf.mpg.de/andersen/phonons
- …