127 research outputs found
Global optical potential for nucleus-nucleus systems from 50 MeV/u to 400 MeV/u
We present a new global optical potential (GOP) for nucleus-nucleus systems,
including neutron-rich and proton-rich isotopes, in the energy range of MeV/u. The GOP is derived from the microscopic folding model with the
complex -matrix interaction CEG07 and the global density presented by S{\~
a}o Paulo group. The folding model well accounts for realistic complex optical
potentials of nucleus-nucleus systems and reproduces the existing elastic
scattering data for stable heavy-ion projectiles at incident energies above 50
MeV/u. We then calculate the folding-model potentials (FMPs) for projectiles of
even-even isotopes, C, O, Ne, Mg,
Si, S, Ar, and Ca, scattered by stable
target nuclei of C, O, Si, Ca Ni, Zr,
Sn, and Pb at the incident energy of 50, 60, 70, 80, 100, 120,
140, 160, 180, 200, 250, 300, 350, and 400 MeV/u. The calculated FMP is
represented, with a sufficient accuracy, by a linear combination of 10-range
Gaussian functions. The expansion coefficients depend on the incident energy,
the projectile and target mass numbers and the projectile atomic number, while
the range parameters are taken to depend only on the projectile and target mass
numbers. The adequate mass region of the present GOP by the global density is
inspected in comparison with FMP by realistic density. The full set of the
range parameters and the coefficients for all the projectile-target
combinations at each incident energy are provided on a permanent open-access
website together with a Fortran program for calculating the microscopic-basis
GOP (MGOP) for a desired projectile nucleus by the spline interpolation over
the incident energy and the target mass number.Comment: 25 pages, 13 figure
Pauli-Spin-Blockade Transport through a Silicon Double Quantum Dot
We present measurements of resonant tunneling through discrete energy levels
of a silicon double quantum dot formed in a thin silicon-on-insulator layer. In
the absence of piezoelectric phonon coupling, spontaneous phonon emission with
deformation-potential coupling accounts for inelastic tunneling through the
ground states of the two dots. Such transport measurements enable us to observe
a Pauli spin blockade due to effective two-electron spin-triplet correlations,
evident in a distinct bias-polarity dependence of resonant tunneling through
the ground states. The blockade is lifted by the excited-state resonance by
virtue of efficient phonon emission between the ground states. Our experiment
demonstrates considerable potential for investigating silicon-based spin
dynamics and spin-based quantum information processing.Comment: 10 pages,3 figure
Spin splitting of upper electron subbands in a SiO2/Si(100)/SiO2 quantum well with in-plane magnetic field
Enhanced collectivity in 74Ni
The neutron-rich nucleus 74Ni was studied with inverse-kinematics inelastic
proton scattering using a 74Ni radioactive beam incident on a liquid hydrogen
targetat a center-of-mass energy of 80 MeV. From the measured de-excitation
gamma-rays, the population of the first 2+ state was quantified. The
angle-integrated excitation cross section was determined to be 14(4) mb. A
deformation length of delta = 1.04(16) fm was extracted in comparison with
distorted wave theory, which suggests that the enhancement of collectivity
established for 70Ni continues up to 74Ni. A comparison with results of shell
model and quasi-particle random phase approximation calculations indicates that
the magic character of Z = 28 or N = 50 is weakened in 74Ni
Spin splitting of upper electron subbands in a SiO<sub>2</sub>/Si(100)/SiO<sub>2</sub> quantum well with in-plane magnetic field
Metallic behaviour in SOI quantum wells with strong intervalley scattering
Supplementary code for the calculation of WL with intervalley scattering available at the publisher's siteInternational audienceThe fundamental properties of valleys are recently attracting growing attention due to electrons in new and topical materials possessing this degree-of-freedom and recent proposals for val-leytronics devices. In silicon MOSFETs, the interest has a longer history since the valley degree of freedom had been identified as a key parameter in the observation of the controversial " metallic behaviour " in two dimensions. However, while it has been recently demonstrated that lifting valley degeneracy can destroy the metallic behaviour, little is known about the role of intervalley scattering. Here, we show that the metallic behaviour can be observed in the presence of strong interval-ley scattering in silicon on insulator (SOI) quantum wells. Analysis of the conductivity in terms of quantum corrections reveals that interactions are much stronger in SOI than in conventional MOSFETs, leading to the metallic behaviour despite the strong intervalley scattering. The prospect of manipulating the valley degree of freedom in materials like AlAs, 1 silicon 2–4 graphene
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