10,725 research outputs found
Quasi-particle random phase approximation with quasi-particle-vibration coupling: application to the Gamow-Teller response of the superfluid nucleus Sn
We propose a self-consistent quasi-particle random phase approximation (QRPA)
plus quasi-particle-vibration coupling (QPVC) model with Skyrme interactions to
describe the width and the line shape of giant resonances in open-shell nuclei,
in which the effect of superfluidity should be taken into account in both the
ground state and the excited states. We apply the new model to the Gamow-Teller
resonance in the superfluid nucleus Sn, including both the isoscalar
spin-triplet and the isovector spin-singlet pairing interactions. The strength
distribution in Sn is well reproduced and the underlying microscopic
mechanisms, related to QPVC and also to isoscalar pairing, are analyzed in
detail.Comment: 32 pages, 11 figures, 4 table
Separable states and the geometric phases of an interacting two-spin system
It is known that an interacting bipartite system evolves as an entangled
state in general, even if it is initially in a separable state. Due to the
entanglement of the state, the geometric phase of the system is not equal to
the sum of the geometric phases of its two subsystems. However, there may exist
a set of states in which the nonlocal interaction does not affect the
separability of the states, and the geometric phase of the bipartite system is
then always equal to the sum of the geometric phases of its subsystems. In this
paper, we illustrate this point by investigating a well known physical model.
We give a necessary and sufficient condition in which a separable state remains
separable so that the geometric phase of the system is always equal to the sum
of the geometric phases of its subsystems.Comment: 13 page
Time-resolved PhotoEmission Spectroscopy on a Metal/Ferroelectric Heterostructure
In thin film ferroelectric capacitor the chemical and electronic structure of
the electrode/FE interface can play a crucial role in determining the kinetics
of polarization switching. We investigate the electronic structure of a
Pt/BaTiO3/SrTiO3:Nb capacitor using time-resolved photoemission spectroscopy.
The chemical, electronic and depth sensitivity of core level photoemission is
used to probe the transient response of different parts of the upper
electrode/ferroelectric interface to voltage pulse induced polarization
reversal. The linear response of the electronic structure agrees quantitatively
with a simple RC circuit model. The non-linear response due to the polarization
switch is demonstrated by the time-resolved response of the characteristic core
levels of the electrode and the ferroelectric. Adjustment of the RC circuit
model allows a first estimation of the Pt/BTO interface capacitance. The
experiment shows the interface capacitance is at least 100 times higher than
the bulk capacitance of the BTO film, in qualitative agreement with theoretical
predictions from the literature.Comment: 7 pages, 10 figures. Submitted to Phys. Rev.
Two monotonic functions involving gamma function and volume of unit ball
In present paper, we prove the monotonicity of two functions involving the
gamma function and relating to the -dimensional volume of the
unit ball in .Comment: 7 page
Transition to Instability in a Kicked Bose-Einstein Condensate
A periodically kicked ring of a Bose-Einstein condensate is considered as a
nonlinear generalization of the quantum kicked rotor. For weak interactions
between atoms, periodic motion (anti-resonance) becomes quasiperiodic (quantum
beating) but remains stable. There exists a critical strength of interactions
beyond which quasiperiodic motion becomes chaotic, resulting in an instability
of the condensate manifested by exponential growth in the number of
noncondensed atoms. Similar behavior is observed for dynamically localized
states (essentially quasiperiodic motions), where stability remains for weak
interactions but is destroyed by strong interactions.Comment: 4 pages, 6 figs. A new affiliation is added. Accepted by Phys. Rev.
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Towards a Unified Description of Isoscalar Giant Monopole Resonances in a Self-Consistent Quasiparticle-Vibration Coupling Approach
"Why is the EoS for tin so soft?" is a longstanding question, which prevents
us from determining the nuclear incompressibility accurately. To
solve this puzzle, a fully self-consistent quasiparticle random phase
approximation (QRPA) plus quasiparticle-vibration coupling (QPVC) approach
based on Skyrme-Hartree-Fock-Bogoliubov is developed. We show that the
many-body correlations introduced by QPVC, which shift the ISGMR energy in Sn
isotopes by about 0.4 MeV more than the energy in Pb, play a crucial
role in providing a unified description of the ISGMR in Sn and Pb isotopes. The
best description of the experimental strength functions is given by SV-K226 and
KDE0, which are characterized by incompressibility values 226 MeV
and 229 MeV, respectively, at mean field level
Interface Electronic Structure in a Metal/Ferroelectric Heterostructure under Applied Bias
The effective barrier height between an electrode and a ferroelectric (FE)
depends on both macroscopic electrical properties and microscopic chemical and
electronic structure. The behavior of a prototypical electrode/FE/electrode
structure, Pt/BaTiO3/Nb-doped SrTiO3, under in-situ bias voltage is
investigated using X-Ray Photoelectron Spectroscopy. The full band alignment is
measured and is supported by transport measurements. Barrier heights depend on
interface chemistry and on the FE polarization. A differential response of the
core levels to applied bias as a function of the polarization state is
observed, consistent with Callen charge variations near the interface.Comment: 9 pages, 8 figures. Submitted to Phys. Rev.
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