888 research outputs found
Plasmons and their interaction with electrons in trilayer graphene
The interaction between electrons and plasmons in trilayer graphene is
investigated within the Overhauser approach resulting in the 'plasmaron'
quasi-particle. This interaction is cast into a field theoretical problem, nd
its effect on the energy spectrum is calculated using improved Wigner-Brillouin
perturbation theory. The plasmaron spectrum is shifted with respect to the bare
electron spectrum by for ABC
stacked trilayer graphene and for ABA trilayer graphene by () for the hyperbolic linear) part of the spectrum. The shift in general
increases with the electron concentration and electron momentum. The
dispersion of plasmarons is more pronounced in \textit{ABC} stacked than in ABA
tacked trilayer graphene, because of the different energy band structure and
their different plasmon dispersion.Comment: arXiv admin note: substantial text overlap with arXiv:1310.623
Empirical description of beta-delayed fission partial half-lives
Background: The process of beta-delayed fission (bDF) provides a versatile
tool to study low-energy fission in nuclei far away from the beta-stability
line, especially for nuclei which do not fission spontaneously. Purpose: The
aim of this paper is to investigate systematic trends in bDF partial
half-lives. Method: A semi-phenomenological framework was developed to
systematically account for the behavior of bDF partial half-lives. Results: The
bDF partial half-life appears to exponentially depend on the difference between
the Q value for beta decay of the parent nucleus and the fission-barrier energy
of the daughter (after beta decay) product. Such dependence was found to arise
naturally from some simple theoretical considerations. Conclusions: This
systematic trend was confirmed for experimental bDF partial half-lives spanning
over 7 orders of magnitudes when using fission barriers calculated from either
the Thomas-Fermi or the liquid-drop fission model. The same dependence was also
observed, although less pronounced, when comparing to fission barriers from the
finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky Integral
method.Comment: accepted for publication in Phys. Rev.
Spin- and valley-dependent transport through arrays of ferromagnetic silicene junctions
We study ballistic transport of Dirac fermions in silicene through arrays of
barriers, of width , in the presence of an exchange field and a tunable
potential of height or depth . The spin- and valley-resolved
conductances as functions of or , exhibit resonances away from the Dirac
point (DP) and close to it a pronounced dip that becomes a gap when a critical
electric field is applied. This gap widens by increasing the number of
barriers and can be used to realize electric field-controlled switching of the
current. The spin and valley polarizations of the current near the
DP increase with or and can reach 100\% for certain of their values.
These field ranges widen significantly by increasing the number of barriers.
Also, and oscillate nearly periodically with the separation between
barriers or wells and can be inverted by reversing .Comment: 9 pages, 43 figures, to appear in PRB, figure resolutions reduced for
siz
Alpha Decay Hindrance Factors: A Probe of Mean Field Wave Functions
A simple model to calculate alpha-decay Hindrance Factors is presented. Using
deformation values obtained from PES calculations as the only input, Hindrance
Factors for the alpha-decay of Rn- and Po-isotopes are calculated. It is found
that the intrinsic structure around the Fermi surface determined by the
deformed mean field plays an important role in determining the hindrance of
alpha-decay. The fair agreement between experimental and theoretical Hindrance
Factors suggest that the wave function obtained from the energy minima of the
PES calculations contains an important part of the correlations that play a
role for the alpha-decay. The calculated HF that emerges from these
calculations render a different interpretation than the commonly assumed
n-particle n-hole picture.Comment: 7 pages, 9 figure
Pairing-excitation versus intruder states in 68Ni and 90Zr
A discussion on the nature of the 0+ states in 68Ni (Z=28, N=40) is presented
and a comparison is made with its valence counterpart 90Zr (Z=40, N=50).
Evidence is given for a 0+ proton intruder state at only ~2.2 MeV excitation
energy in 68Ni, while the analogous neutron intruder states in 90Zr reside at
4126 keV and 5441 keV. The application of a shell-model description of 0+
intruder states reveals that many pair-scattered neutrons across N=40 have to
be involved to explain the low excitation energy of the proton-intruder
configuration in 68Ni.Comment: 10 pages, 2 figures, 1 tabl
- …