1,455 research outputs found
Effect of Hexagonal Boron Nitride on Energy Band Gap of Graphene Antidot Structures
The zero band gap (Eg) graphene becomes narrow Eg semiconductor when graphene
is patterned with periodic array of hexagonal shaped antidots, the resultant is
the hexagonal Graphene Antidot Lattice (hGAL). Based on the number of atomic
chains between antidots, hGALs can be even and odd. The even hGALs (ehGAL) are
narrow Eg semiconductors and odd hGALs (ohGAL) are semi-metals. The Eg opening
up by hGALs is not sufficient to operate a realistic switching transistor. Also
hGAL transistors realized on Si/SiO2 substrate are suffering with low carrier
mobility and ON-OFF current ratio. In order to achieve a sizable Eg with good
mobility, AB Bernal stacked hGALs on hexagonal Boron Nitride (hBN), ABA Bernal
stacked hBN / hGAL / hBN sandwiched structures and AB misaligned hGAL /hBN
structures are reported here for the first time. Using the first principles
method the electronic structure calculations are performed. A sizable Eg of
about 1.04 eV (940+100 meV) is opened when smallest neck width medium radius
ehGAL supported on hBN and about 1.1 eV (940 + 200 meV) is opened when the same
is sandwiched between hBN layers. A band gap on the order of 71 meV is opened
for Bernal stacked ohGAL / hBN and nearly 142 meV opened for hBN / ohGAL /hBN
structures for smallest radius and width of nine atomic chains between
antidots. Unlike a misaligned graphene on hBN, the misaligned ohGAL/hBN
structure shows increased Eg. This study could open up new ways of band gap
engineering for graphene based nanostructures. Keywords: Graphene, graphene
antidots, hexagonal boron nitride, band structure, band gap engineeringComment: 14 pages, 5 figures, Innovative Systems Design and Engineering,Vol 3,
No 12 (2012
Uncertainties in nuclear transition matrix elements for neutrinoless decay II: the heavy Majorana neutrino mass mechanism
Employing four different parametrization of the pairing plus multipolar type
of effective two-body interaction and three different parametrizations of
Jastrow-type of short range correlations, the uncertainties in the nuclear
transition matrix elements due to the exchange of heavy
Majorana neutrino for the transition of neutrinoless
double beta decay of Zr, Zr, Mo, Mo, Ru,
Pd, Te and Nd isotopes in the PHFB model are
estimated to be around 25%. Excluding the nuclear transition matrix elements
calculated with Miller-Spenser parametrization of Jastrow short range
correlations, the uncertainties are found to be 10%-15% smaller
Nuclear deformation and neutrinoless double- decay of Zr, Mo, Ru, Pd, Te and Nd nuclei in mass mechanism
The decay of Zr, Mo,
Ru, Pd, Te and Nd isotopes for the
transition is studied in the Projected Hartree-Fock-Bogoliubov
framework. In our earlier work, the reliability of HFB intrinsic wave functions
participating in the decay of the above mentioned nuclei
has been established by obtaining an overall agreement between the
theoretically calculated spectroscopic properties, namely yrast spectra,
reduced : transition probabilities, quadrupole moments
, gyromagnetic factors as well as half-lives
for the transition and the available
experimental data. In the present work, we study the decay for the transition in the mass mechanism
and extract limits on effective mass of light as well as heavy neutrinos from
the observed half-lives using nuclear
transition matrix elements calculated with the same set of wave functions.
Further, the effect of deformation on the nuclear transition matrix elements
required to study the decay in the mass
mechanism is investigated. It is noticed that the deformation effect on nuclear
transition matrix elements is of approximately same magnitude in and decay.Comment: 15 pages, 1 figur
A note on the Gauss decomposition of the elliptic Cauchy matrix
Explicit formulas for the Gauss decomposition of elliptic Cauchy type
matrices are derived in a very simple way. The elliptic Cauchy identity is an
immediate corollary.Comment: 5 page
The positron double- decay with emission of two neutrinos in the nuclei Ru, Pd, Cd and Cd
Theoretical results for %the positron double- decay
with emission of two neutrinos in the nuclei Ru, Pd, Cd
and Cd are presented. The study employs the Hartree-Fock-Bogoliubov
model to obtain the wave functions of the parent and daughter nuclei, in
conjunction with the summation method to estimate the double beta decay nuclear
matrix elements. The reliability of the intrinsic wave functions of
Ru, Mo, Pd and Cd nuclei are
tested by comparing the theoretically calculated spectroscopic properties with
the available experimental data. Calculated half-lives of Ru, Pd, Cd and Cd nuclei for 2 , 2 and 2 modes are presented.
The effect of deformation on the nuclear transition matrix element
is also studied.Comment: Submitted to EPJ
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