3,176 research outputs found
-AlN-Mg(OH) vdW Bilayer Heterostructure: Tuning the excitonic characteristics
Motivated by recent studies that reported the successful synthesis of
monolayer Mg(OH) [Suslu \textit{et al.}, Sci. Rep. \textbf{6}, 20525
(2016)] and hexagonal (\textit{h}-)AlN [Tsipas \textit{et al}., Appl. Phys.
Lett. \textbf{103}, 251605 (2013)], we investigate structural, electronic, and
optical properties of vertically stacked -AlN and Mg(OH), through
\textit{ab initio} density-functional theory (DFT), many-body quasi-particle
calculations within the GW approximation, and the Bethe-Salpeter equation
(BSE). It is obtained that the bilayer heterostructure prefers the
stacking having direct band gap at the with Type-II band
alignment in which the valance band maximum and conduction band minimum
originate from different layer. Regarding the optical properties, the imaginary
part of the dielectric function of the individual layers and hetero-bilayer are
investigated. The hetero-bilayer possesses excitonic peaks which appear only
after the construction of the hetero-bilayer. The lowest three exciton peaks
are detailedly analyzed by means of band decomposed charge density and the
oscillator strength. Furthermore, the wave function calculation shows that the
first peak of the hetero-bilayer originates from spatially indirect exciton
where the electron and hole localized at -AlN and Mg(OH),
respectively, which is important for the light harvesting applications.Comment: Accepted by Physical Review
How many phases meet at the chiral critical point?
We explore the phase diagram of NJL-type models near the chiral critical
point allowing for phases with spatially inhomogeneous chiral condensates. In
the chiral limit it turns out that the region in the mean-field phase diagram
where those phases are energetically preferred very generically reaches out to
the chiral critical point. The preferred inhomogeneous ground state in this
vicinity possibly resembles a lattice of domain wall solitons. This raises the
question of their relevance for the phase diagram of QCD.Comment: 7 pages, 1 figure; v2: minor corrections, as published in PR
Kaon properties and cross sections in nuclear medium
Results for the reactions in nuclear matter
of Ref. nucl-th/0004011 are presented. To evaluate the in-medium modification
of the reaction amplitude as a function of the baryonic density we introduce
relativistic, mean-field potentials for the initial, final and intermediate
mesonic and baryonic states in the resonance model. These vector and scalar
potentials were calculated using the quark meson coupling model. Contrary to
earlier work which has not allowed for the change of the cross section in
medium, we find that the data for kaon production at SIS energies are
consistent with a repulsive -nucleus potential.Comment: 5 pages, 3 postscript figures included, uses iopart.cls and
iopart10.clo (included), presented by K.T. at the 5th International
Conference on Strangeness in Quark Matter, July 20 - 25, 2000, Berkeley,
California, to be published in the proceedings, J. Phys. G. An explanation
has been added in Sec. 3 with a new figur
Statistical hadronization of charm: from FAIR to the LHC
We discuss the production of charmonium in nuclear collisions within the
framework of the statistical hadronization model. We demonstrate that the model
reproduces very well the availble data at RHIC. We provide predictions for the
LHC energy where, dependently on the charm production cross section, a
dramatically different behaviour of charmonium production as a function of
centrality might be expected. We extend our predictions for charm production
towards the threshold energies, where charm is expected to be measured at the
future FAIR facility.Comment: 4 pages, 3 figures; proceedings of QM200
Testing Lorentz Invariance by Comparing Light Propagation in Vacuum and Matter
We present a Michelson-Morley type experiment for testing the isotropy of the
speed of light in vacuum and matter. The experiment compares the resonance
frequency of a monolithic optical sapphire resonator with the resonance
frequency of an orthogonal evacuated optical cavity made of fused silica while
the whole setup is rotated on an air bearing turntable once every 45 s.
Preliminary results yield an upper limit for the anisotropy of the speed of
light in matter (sapphire) of \Delta c/c < 4x10^(-15), limited by the frequency
stability of the sapphire resonator operated at room temperature. Work to
increase the measurement sensitivity by more than one order of magnitude by
cooling down the sapphire resonator to liquid helium temperatures (LHe) is
currently under way.Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry,
Bloomington, Indiana, June 28-July 2, 201
Test of the isotropy of the speed of light using a continuously rotating optical resonator
We report on a test of Lorentz invariance performed by comparing the
resonance frequencies of one stationary optical resonator and one continuously
rotating on a precision air bearing turntable. Special attention is paid to the
control of rotation induced systematic effects. Within the photon sector of the
Standard Model Extension, we obtain improved limits on combinations of 8
parameters at a level of a few parts in . For the previously least
well known parameter we find . Within the Robertson-Mansouri-Sexl test theory, our measurement
restricts the isotropy violation parameter to
, corresponding to an eightfold improvement with
respect to previous non-rotating measurements.Comment: 4 pages, 3 figures, to appear in Phys. Rev. Let
Strong Coupling Characterisation of Quasi-1D polarons in cylindrical QW-wires
Cataloged from PDF version of article.We retrieve, within the strong-coupling theory, the quasi-one dimensional analog of the standard optical polaron relevant to a cylindrical quantum well wire. Under the assumption of perfect confinement the ground state binding energy, effective polaronic mass and the phonon-coupling-induced potential well profiles are given as a function of the wire radius and the electron-phonon interaction strength
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