4,664 research outputs found
Theory of high energy features in angle-resolved photo-emission spectra of hole-doped cuprates
The recent angle-resolved photoemission measurements performed up to binding
energies of the order of 1eV reveals a very robust feature: the nodal
quasi-particle dispersion breaks up around 0.3-0.4eV and reappears around
0.6-0.8eV. The intensity map in the energy-momentum space shows a waterfall
like feature between these two energy scales. We argue and numerically
demonstrate that these experimental features follow naturally from the strong
correlation effects built in the familiar t-J model, and reflect the connection
between the fermi level and the lower Hubbard band. The results were obtained
by a mean field theory that effectively projects electrons by quantum
interference between two bands of fermions instead of binding slave particles.Comment: 5 pages 2 fig
Symmetry restrictions in chirality dependence of physical properties of single wall nanotubes
We investigate the chirality dependence of physical properties of nanotubes
which are wrapped by the planar hexagonal lattice including graphite and boron
nitride sheet, and reveal its symmetry origin. The observables under
consideration are of scalar, vector and tensor types. These exact chirality
dependence obtained are useful to verify the experimental and numerical results
and propose accurate empirical formulas. Some important features of physical
quantities can also be extracted by only considering the symmetry restrictions
without complicated calculations.Comment: 5 pages, 1 figure
The vitellogenesis-inhibiting hormone (SpVIH) of the crab Scylla paramamosain is not likely to have a vitellogenesis-inhibiting function in the ovary
The function and molecular characterization of the previously reported crab (Scylla paramamosain) vitellogenesis inhibiting hormone SpVIH is still unclear. In this experiment, SpVIH’s bioinformatic and functional characterizations were analyzed. Sequence analysis showed SpVIH was clustered with several type II MIH/GIHs of the Brachyura. The expression of SpVIH in the eyestalk was low in the early ovarian developmental stage I and increased with the advancement of ovary maturation. Interestingly, the SpVIH transcript was still at a high level in the ovary of females at the middle to late maturation stage. SpVIH’s function was studied according to the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) in the ovary and hepatopancreas after incubation with SpVIH-dsRNA and recombinant SpVIH protein (rSpVIH). In vitro assay results indicated that rSpVIH has a significant stimulative effect on the expression of Vg in the hepatopancreas in the middle stage of vitellogenesis and in the ovary of each vitellogenesis stage. However, SpVIH-dsRNA has no significant effect on the expression of Vg when SpVIH-dsRNA is introduced to the ovary and hepatopancreas at the early, middle, and late stages of vitellogenesis. Furthermore, the co-incubation experiment result indicated that the eyestalk consists of factor(s) that can significantly up-regulate the expression of Vg in the ovary, with a further combination of dsVIH and eyestalk under incubation, the significant increase of Vg-mRNA expression levels were also found in the ovary of four ovarian development stages of S. paramamosain. Contrary to the previous reports, SpVIH does not possess a vitellogenesis-inhibiting function but can promote vitellogenesis in the ovary and hepatopancreas
Non-Abelian Medium Effects in Quark-Gluon Plasma
Based on the kinetic theory, the non-Abelian medium property of hot
Quark-Gluon Plasma is investigated. The nonlinearity of the plasma comes from
two aspects: The nonlinear wave-wave interaction and self-interaction of color
field. The non-Abelian color permittivity is obtained by expanding the kinetic
equations to third order. As an application, the nonlinear Landau damping rate
and the nonlinear eigenfrequency shift are calculated in the longwave length
limit.Comment: 12 pages(Revtex), no figure
A Note on Normal Forms of Quantum States and Separability
We study the normal form of multipartite density matrices. It is shown that
the correlation matrix (CM) separability criterion can be improved from the
normal form we obtained under filtering transformations. Based on CM criterion
the entanglement witness is further constructed in terms of local orthogonal
observables for both bipartite and multipartite systems.Comment: 8 page
Growth and thermal stability of TiN/ZrAlN: Effect of internal interfaces
Wear resistant hard films comprised of cubic transition metal nitride (c-TMN) and metastable c-AlN with coherent interfaces have a confined operating envelope governed by the limited thermal stability of metastable phases. However, equilibrium phases (c-TMN and wurtzite(w)-AlN) forming semicoherent interfaces during film growth offer higher thermal stability. We demonstrate this concept for a model multilayer system with TiN and ZrAlN layers where the latter is a nanocomposite of ZrN- and AlN- rich domains. The interfaces between the domains are tuned by changing the AlN crystal structure by varying the multilayer architecture and growth temperature. The interface energy minimization at higher growth temperature leads to formation of semicoherent interfaces between w-AlN and c-TMN during growth of 15 nm thin layers. Ab initio calculations predict higher thermodynamic stability of semicoherent interfaces between c-TMN and w-AlN than isostructural coherent interfaces between c-TMN and c-AlN. The combination of a stable interface structure and confinement of w-AlN to nm-sized domains by its low solubility in c-TMN in a multilayer, results in films with a stable hardness of 34 GPa even after annealing at 1150 °C.Peer ReviewedPostprint (author's final draft
Reconsideration of Second Harmonic Generation from neat Air/Water Interface: Broken of Kleinman Symmetry from Dipolar Contribution
It has been generally accepted that there are significant quadrupolar and
bulk contributions to the second harmonic generation (SHG) reflected from the
neat air/water interface, as well as common liquid interfaces. Because there
has been no general methodology to determine the quadrupolar and bulk
contributions to the SHG signal from a liquid interface, this conclusion was
reached based on the following two experimental phenomena. Namely, the broken
of the macroscopic Kleinman symmetry, and the significant temperature
dependence of the SHG signal from the neat air/water interface. However,
because sum frequency generation vibrational spectroscopy (SFG-VS) measurement
of the neat air/water interface observed no apparent temperature dependence,
the temperature dependence in the SHG measurement has been reexamined and
proven to be an experimental artifact. Here we present a complete microscopic
analysis of the susceptibility tensors of the air/water interface, and show
that dipolar contribution alone can be used to address the issue of broken of
the macroscopic Kleinman symmetry at the neat air/water interface. Using this
analysis, the orientation of the water molecules at the interface can be
obtained, and it is consistent with the measurement from SFG-VS. Therefore, the
key rationales to conclude significantly quadrupolar and bulk contributions to
the SHG signal of the neat air/water interface can no longer be considered as
valid as before. This new understanding of the air/water interface can shed
light on our understanding of the nonlinear optical responses from other
molecular interfaces as well
Imbalanced superfluid state in an annular disk
The imbalanced superfluid state of spin-1/2 fermions with s-wave pairing is
numerically studied by solving the Bogoliubov-de-Gennes equation at zero
temperature in an annular disk geometry with narrow radial width. Two distinct
types of systems are considered. The first case may be relevant to heavy
fermion superconductors, where magnetic field causes spin imbalance via Zeeman
interaction and the system is studied in a grand canonical ensemble. As the
magnetic field increases, the system is transformed from the uniform superfluid
state to the Fulde-Ferrell-Larkin-Ovchinnikov state, and finally to the spin
polarized normal state. The second case may be relevant to cold fermionic
systems, where the numbers of fermions of each species are fixed as in a
canonical ensemble. In this case, the groundstate depends on the pairing
strength. For weak pairing, the order parameter exhibits a periodic domain wall
lattice pattern with a localized spin distribution at low spin imbalance, and a
sinusoidally modulated pattern with extended spin distribution at high spin
imbalance. For strong pairing, the phase separation between superfluid state
and polarized normal state is found to be more preferable, while the increase
of spin imbalance simply changes the ratio between them.Comment: 8 pages, 10 figures. Final version with references added and
discussion on Sarma state remove
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