69,985 research outputs found
Nonequilibrium electron transport in strongly correlated molecular junctions
We investigate models of molecular junctions which constitute minimal
Hamiltonians to account for zero-bias-anomaly and the satellite features of
inelastic transport by molecular phonons. Through nonlinear transport
calculations with the imaginary-time nonequilibrium formalism, a HOMO-LUMO
model with Anderson-Holstein interaction is shown to produce co-tunneling
conductance peak in the vicinity of Kondo resonance which is mediated by a
re-emergent many-body resonance assisted by phonon excitations at bias equal to
the phonon frequency. Destruction of the resonance leads to
negative-differential-resistance in the sequential tunneling regime
Spin-triplet s-wave local pairing induced by Hund's rule coupling
We show within the dynamical mean field theory that local multiplet
interactions such as Hund's rule coupling produce local pairing
superconductivity in the strongly correlated regime. Spin-triplet
superconductivity driven by the Hund's rule coupling emerges from the pairing
mediated by local fluctuations in pair exchange. In contrast to the
conventional spin-triplet theories, the local orbital degrees of freedom has
the anti-symmetric part of the exchange symmetry, leaving the spatial part as
fully gapped and symmetric s-wave.Comment: 9 pages, 7 figure
Secure Identification of Free-Floating Planets
Among the methods proposed to detect extrasolar planets, microlensing is the
only technique that can detect free-floating planets. Free-floating planets are
detected through the channel of short-duration isolated lensing events.
However, if a seemingly isolated planetary event is detected, it is difficult
to firmly conclude that the event is caused by a free-floating planet because a
wide-separation planet can also produce an isolated event. There were several
methods proposed to break the degeneracy between the isolated planetary events
produced by the free-floating and wide-separation planets, but they are
incomplete. In this paper, we show that free-floating planets can be securely
identified by conducting astrometric follow-up observations of isolated events
to be detected in future photometric lensing surveys by using high-precision
interferometers to be operated contemporarily with the photometric surveys. The
method is based on the fact that astrometric lensing effect covers much longer
range of the lens-source separation than the photometric effect. We demonstrate
that several astrometric follow-up observations of isolated planetary events
associated with source stars brighter than by using the {\it Space
Interferometry Mission} with an exposure time of for
each observation will make it possible to measure the centroid shift induced by
primaries with projected separations up to . Therefore, the
proposed method is far more complete than previously proposed methods that are
flawed by the limited applicability only to planets with projected separations
or planets accompanied by bright primaries.Comment: 5 pages including 2 figure
Prediction of vertical bearing capacity of waveform micropile
This study proposes a predictive equation for bearing capacity considering the behaviour characteristics of a waveform micropile that can enhance the bearing capacity of a conventional micropile. The bearing capacity of the waveform micropile was analysed by a three-dimensional numerical model with soil and pile conditions obtained from the field and centrifuge tests. The load-transfer mechanism of the waveform micropile was revealed by the numerical analyses, and a new predictive equation for the bearing capacity was proposed. The bearing capacities of the waveform micropile calculated by the new equation were comparable with those measured from the field and centrifuge tests. This validated a prediction potential of the new equation for bearing capacity of waveform micropiles
Imaginary-time formulation of steady-state nonequilibrium in quantum dot models
We examine the recently proposed imaginary-time formulation for strongly
correlated steady-state nonequilibrium for its range of validity and discuss
significant improvements in the analytic continuation of the Matsubara voltage
as well as the fermionic Matsubara frequency. The discretization error in the
conventional Hirsch-Fye algorithm has been compensated in the Fourier
transformation with reliable small frequency behavior of self-energy. Here we
give detailed discussions for generalized spectral representation ansatz by
including high order vertex corrections and its numerical analytic continuation
procedures. The differential conductance calculations agree accurately with
existing data from other nonequilibrium transport theories. It is verified
that, at finite source-drain voltage, the Kondo resonance is destroyed at bias
comparable to the Kondo temperature. Calculated coefficients in the scaling
relation of the zero bias anomaly fall within the range of experimental
estimates.Comment: 16 pages, 10 figures, Comparison to other theories adde
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