2,456 research outputs found
Observation of particle hole asymmetry and phonon excitations in non-Fermi liquid systems: A high-resolution photoemission study of ruthenates
We investigate the temperature evolution of the electronic states in the
vicinity of the Fermi level of a non-Fermi liquid (NFL) system, CaRuO3 using
ultra high-resolution photoemission spectroscopy; isostructural SrRuO3
exhibiting Fermi liquid behavior despite similar electron interaction
parameters as that of CaRuO3, is used as a reference. High-energy resolution in
this study helps to reveal particle-hole asymmetry in the excitation spectra of
CaRuO3 in contrast to that in SrRuO3. In addition, we observe signature of
phonon excitations in the photoemission spectra of CaRuO3 at finite
temperatures while these are weak in SrRuO3.Comment: 4 pages including 3 figure
Magnetic Response in a Zigzag Carbon Nanotube
Magnetic response of interacting electrons in a zigzag carbon nanotube
threaded by a magnetic flux is investigated within a Hartree-Fock mean field
approach. Following the description of energy spectra for both non-interacting
and interacting cases we analyze the behavior of persistent current in
individual branches of a nanotube. Our present investigation leads to a
possibility of getting a filling-dependent metal-insulator transition in a
zigzag carbon nanotube.Comment: 9 pages, 14 figure
Elasticity of DNA and the effect of Dendrimer Binding
Negatively charged DNA can be compacted by positively charged dendrimers and
the degree of compaction is a delicate balance between the strength of the
electrostatic interaction and the elasticity of DNA. We report various elastic
properties of short double stranded DNA (dsDNA) and the effect of dendrimer
binding using fully atomistic molecular dynamics and numerical simulations. In
equilibrium at room temperature, the contour length distribution P(L) and
end-to-end distance distribution P(R) are nearly Gaussian, the former gives an
estimate of the stretch modulus {\gamma}_1 of dsDNA in quantitative agreement
with the literature value. The bend angle distribution P({\theta}) of the dsDNA
also has a Gaussian form and allows to extract a persistence length, L_p of 43
nm. When the dsDNA is compacted by positively charged dendrimer, the stretch
modulus stays invariant but the effective bending rigidity estimated from the
end-to-end distance distribution decreases dramatically due to backbone charge
neutralization of dsDNA by dendrimer. We support our observations with
numerical solutions of the worm-like-chain (WLC) model as well as using
non-equilibrium dsDNA stretching simulations. These results are helpful in
understanding the dsDNA elasticity at short length scales as well as how the
elasticity is modulated when dsDNA binds to a charged object such as a
dendrimer or protein.Comment: 21 pages, 5 figure
Effect of non-magnetic impurities on the magnetic states of anatase TiO
The electronic and magnetic properties of TiO, TiO,
TiON, and TiOF compounds have been studied
by using \emph{ab initio} electronic structure calculations. TiO is found
to evolve from a wide-band-gap semiconductor to a narrow-band-gap semiconductor
to a half-metallic state and finally to a metallic state with oxygen vacancy,
N-doping and F-doping, respectively. Present work clearly shows the robust
magnetic ground state for N- and F-doped TiO. The N-doping gives rise to
magnetic moment of 0.4 at N-site and 0.1 each at
two neighboring O-sites, whereas F-doping creates a magnetic moment of
0.3 at the nearest Ti atom. Here we also discuss the possible
cause of the observed magnetic states in terms of the spatial electronic charge
distribution of Ti, N and F atoms responsible for bond formation.Comment: 11 pages, 4 figures To appear J. Phys.: Condens. Matte
Evolution of the Kondo resonance feature and its relationship to spin-orbit coupling across the quantum critical point in Ce2Rh{1-x}CoxSi3
We investigate the evolution of the electronic structure of Ce2Rh{1-x}CoxSi3
as a function of x employing high resolution photoemission spectroscopy. Co
substitution at the Rh sites in antiferromagnetic Ce2RhSi3 leads to a
transition from an antiferromagnetic system to a Kondo system, Ce2CoSi3 via the
Quantum Critical Point (QCP). High resolution photoemission spectra reveal
distinct signature of the Kondo resonance feature (KRF) and its spin orbit
split component (SOC) in the whole composition range indicating finite Kondo
temperature scale at the quantum critical point. We observe that the intensity
ratio of the Kondo resonance feature and its spin orbit split component,
KRF/SOC gradually increases with the decrease in temperature in the strong
hybridization limit. The scenario gets reversed if the Kondo temperature
becomes lower than the magnetic ordering temperature. While finite Kondo
temperature within the magnetically ordered phase indicates applicability of
the spin density wave picture at the approach to QCP, the dominant temperature
dependence of the spin-orbit coupled feature suggests importance of spin-orbit
interactions in this regime.Comment: 6 figure
Correlation and surface effects in Vanadium Oxides
Recent photoemission experiments have shown strong surface modifications in
the spectra from vanadium oxides as (V,Cr)_2O_3 or
(Sr,Ca)VO_3. The effective mass is enhanced at the surface and the coherent
part of the surface spectrum is narrowed as compared to the bulk. The
quasiparticle weight is more sensitive at the surface than in the bulk against
bandwidth variations. We investigate these effects theoretically considering
the single-band Hubbard model for a film geometry. A simplified dynamical
mean-field scheme is used to calculate the main features of the interacting
layer-dependent spectral function. It turns out that the experimentally
confirmed effects are inherent properties of a system of strongly correlated
electrons. The reduction of the weight and the variance of the coherent part of
the surface spectrum can be traced back to the reduced surface coordination
number. Surface correlation effects can be strongly amplified by changes of the
hopping integrals at the surface.Comment: to appear in PRB; 8 pages, 6 figure
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