14,472 research outputs found
On determination of the geometric cosmological constant from the OPERA experiment of superluminal neutrinos
The recent OPERA experiment of superluminal neutrinos has deep consequences
in cosmology. In cosmology a fundamental constant is the cosmological constant.
From observations one can estimate the effective cosmological constant
which is the sum of the quantum zero point energy
and the geometric cosmological constant . The
OPERA experiment can be applied to determine the geometric cosmological
constant . It is the first time to distinguish the contributions of
and from each other by experiment. The
determination is based on an explanation of the OPERA experiment in the
framework of Special Relativity with de Sitter space-time symmetry.Comment: 7 pages, no figure
Long-range adiabatic quantum state transfer through a tight-binding chain as a quantum data bus
We introduce a scheme based on adiabatic passage that allows for long-range
quantum communication through tight-binding chain with always-on interaction.
By adiabatically varying the external gate voltage applied on the system, the
electron can be transported from the sender's dot to the aim one.We numerically
solve the Schr\"odinger equation for a system with a given number of quantum
dots. It is shown that this scheme is a simple and efficient protocol to
coherently manipulate the population transfer under suitable gate pulses. The
dependence of the energy gap and the transfer time on system parameters is
analyzed and shown numerically. Our method provides a guidance for future
realization of adiabatic quantum state transfer in experiments.Comment: 7 pages, 5 figures. arXiv admin note: text overlap with
arXiv:1206.671
Bias-induced insulator-metal transition in organic electronics
We investigate the bias-induced insulator-metal transition in organic
electronics devices, on the basis of the Su-Schrieffer-Heeger model combined
with the non-equilibrium Green's function formalism. The insulator-metal
transition is explained with the energy levels crossover that eliminates the
Peierls phase and delocalizes the electron states near the threshold voltage.
This may account for the experimental observations on the devices that exhibit
intrinsic bistable conductance switching with large on-off ratio.Comment: 6 pages, 3 figures. To appear in Applied Physics Letter
Optical properties of coupled metal-semiconductor and metal-molecule nanocrystal complexes: the role of multipole effects
We investigate theoretically the effects of interaction between an optical
dipole (semiconductor quantum dot or molecule) and metal nanoparticles. The
calculated absorption spectra of hybrid structures demonstrate strong effects
of interference coming from the exciton-plasmon coupling. In particular, the
absorption spectra acquire characteristic asymmetric lineshapes and strong
anti-resonances. We present here an exact solution of the problem beyond the
dipole approximation and find that the multipole treatment of the interaction
is crucial for the understanding of strongly-interacting exciton-plasmon
nano-systems. Interestingly, the visibility of the exciton resonance becomes
greatly enhanced for small inter-particle distances due to the interference
phenomenon, multipole effects, and electromagnetic enhancement. We find that
the destructive interference is particularly strong. Using our exact theory, we
show that the interference effects can be observed experimentally even in the
exciting systems at room temperature.Comment: 9 page
Computational Study of Halide Perovskite-Derived ABX Inorganic Compounds: Chemical Trends in Electronic Structure and Structural Stability
The electronic structure and energetic stability of ABX halide
compounds with the cubic and tetragonal variants of the perovskite-derived
KPtCl prototype structure are investigated computationally within the
frameworks of density-functional-theory (DFT) and hybrid (HSE06) functionals.
The HSE06 calculations are undertaken for seven known ABX compounds
with A = K, Rb and Cs, and B = Sn, Pd, Pt, Te, and X = I. Trends in band gaps
and energetic stability are identified, which are explored further employing
DFT calculations over a larger range of chemistries, characterized by A = K,
Rb, Cs, B = Si, Ge, Sn, Pb, Ni, Pd, Pt, Se and Te and X = Cl, Br, I. For the
systems investigated in this work, the band gap increases from iodide to
bromide to chloride. Further, variations in the A site cation influences the
band gap as well as the preferred degree of tetragonal distortion. Smaller A
site cations such as K and Rb favor tetragonal structural distortions,
resulting in a slightly larger band gap. For variations in the B site in the
(Ni, Pd, Pt) group and the (Se, Te) group, the band gap increases with
increasing cation size. However, no observed chemical trend with respect to
cation size for band gap was found for the (Si, Sn, Ge, Pb) group. The findings
in this work provide guidelines for the design of halide ABX compounds
for potential photovoltaic applications
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