ABSTRACT
Ferroelectric (FE) materials, including BiFeO3 , P(VDF-TrFE), and CuInP2 S6 , are a type of dielectric material with a unique, spontaneous electric polarization that can be reversed by applying an external electric field. The combination of FE and low-dimensional materials produces synergies, sparking significant research interest in solar cells, photodetectors (PDs), nonvolatile memory, and so on. The fundamental aspects of FE materials, including the origin of FE polarization, extrinsic FE materials, and FE polarization quantification are first discussed. Next, the state-of-the-art of FE-based optoelectronic devices is focused. How FE materials affect the energy band of channel materials and how device structures influence PD performance are also summarized. Finally, the future directions of this rapidly growing field are discussed.
ABSTRACT
Double ionization of helium by a single intense (above 10^{18} W/cm^{2}) linearly polarized extreme ultraviolet laser pulse is studied by numerically solving the full-dimensional time-dependent Schrödinger equation. For the laser intensities well beyond the perturbative limit, novel gridlike interference fringes are found in the correlated energy spectrum of the two photoelectrons. The interference can be traced to the multitude of two-electron wave packets emitted at different ionization times. A semianalytical model for the dressed two-photon double ionization is shown to qualitatively account for the interference patterns in the joint energy spectrum. Similar signatures of interferences between transient induced time-delayed ionization bursts are expected for other atomic and molecular multielectron systems.
ABSTRACT
We theoretically and experimentally investigate the photon momentum transfer in single-photon double ionization of helium at various large photon energies. We find that the forward shifts of the momenta along the light propagation of the two photoelectrons are roughly proportional to their fraction of the excess energy. The mean value of the forward momentum is about 8/5 of the electron energy divided by the speed of light. This holds for fast and slow electrons despite the fact that the energy sharing is highly asymmetric and the slow electron is known to be ejected by secondary processes of shake off and knockout rather than directly taking its energy from the photon. The biggest deviations from this rule are found for the region of equal energy sharing where the quasifree mechanism dominates double ionization.
ABSTRACT
We study the ionization of atoms by very intense linearly polarized pulse with moderately high frequency by numerically solving the time-dependent Schrödinger equation (TDSE). In this regime, the photon energy exceeds the ionization potential allowing for one-photon ionization which is, however, strongly influenced by strong nonlinear photon-atom interactions. We find that the onset of atomic stabilization can be monitored by the appearance of a dynamic interference pattern in the photoelectron spectrum.
ABSTRACT
High angular momentum partial waves are indispensable in the numerical calculations of the time-dependent Schrödinger equation (TDSE) for the interaction between atoms and strong long-wavelength laser pulses. In these cases, the widely-applied Lanczos propagator, used to solve the TDSE, requires an extremely small time step to be convergent. By splitting out the centrifugal potential from the whole Hamiltonian, we demonstrate that the stiffness of the TDSE can be reduced and a rather large time step is allowed for the present Split-Lanczos propagator. Compared with the ordinary Lanczos propagator, the efficiency of the propagation can be improved by more than 100 times for large angular momentum in present tests.
ABSTRACT
By using a model based on the second-order time-dependent perturbation theory, we show that the nonsequential two-photon double ionization of He can be understood in a virtual sequential picture: to excite the final double continuum state |k_{1},k_{2}⟩ by absorbing two photons from the ground state |1s^{2},^{1}S_{0}⟩, the single continuum states |1s,k_{1}⟩ and |1s,k_{2}⟩ serve as the dominant intermediate states. This virtual sequential picture is verified by the perfect agreement of the total ionization cross section, respectively, calculated by this model and by the sophisticated numerical solution to the full-dimensional time-dependent Schrödinger equation. This model, without the consideration of the electron correlation in the final double continuum state, works well for a wide range of laser parameters extending from the nonsequential to the sequential regime. The present Letter demonstrates that the electron correlation in the final double continuum state is not important in evaluating the total cross section, while it is indispensable for an accurate computation of a triply differential cross section. In addition, the virtual sequential picture bridges the sequential and nonsequential two-photon double ionization and reveals connections and distinctions between them.
ABSTRACT
We select the peptide mimics of blood group A antigen by a monoclonal anti-A from a phage display 15-mer peptide library. Monoclonal anti-A was used in biopanning a phage display 15-mer peptide library. After four rounds of panning, ELISA was carried out to confirm the positive phage clones. The exogenous DNAs of the positive phages were sequenced and the corresponding amino acid sequences were deduced. Both the synthesized peptide and the phage clones were used to bind to anti-A in competitive ELISA. Erythrocyte agglutination inhibition tests were carried out to determine the mimic ability of the free synthesized peptide to the natural blood group A antigen. Computer softwares were used to simulate the interaction between the peptide and anti-A. After four rounds of biopanning, the eluted phage reached an enrichment of approximately 1600 times. Thirty-seven phage clones were chosen randomly and amplified. There were eleven clones that interacted specifically with anti-A in ELISA. DNA sequencing of the inserted oligonucleotide revealed that nine clones present a same peptide - TRWLVYFSRPYLVAT (named TRW) and each of the other two clones presented a different peptide. The synthesized free peptide TRW could inhibit the interaction of both phage displayed peptide and group A red blood cell with anti-A in competitive ELISA and hemagglutination inhibition test. Both the peptide TRW and the natural group A antigen were docked into a same cavity of anti-A in a computer simulation assay. The results indicate that peptide TRW can mimic blood group A antigen. It may be used as a proxy of natural blood group A antigen in clinical application.
Subject(s)
ABO Blood-Group System/chemistry , Antibodies, Monoclonal/chemistry , Peptide Library , ABO Blood-Group System/genetics , Amino Acid Sequence , Erythrocytes/chemistry , Humans , Molecular Sequence DataABSTRACT
AIM: To explore whether the activation-induced cytidine deaminase(AICDA) gene 8408 C/T polymorphism is related to adult atopic asthma and the level of plasma IgE. METHODS: The polymorphism of AICDA gene was detected by PCR and restriction fragment length polymorphism (PCR-RFLP). RESULTS: The frequencies of 8408T/T genotype had significant difference (P<0.05) between adult asthma patients and control group, while the frequencies of T allele between two groups were not significantly different. The total plasma IgE level in adult atopic asthma patients with 8408T/T genotype was higher than that in the patients with C/C and C/T genotypes(P<0.05). CONCLUSION: The 8408 T/T genotype of AICDA is correlated with atopic asthma and total plasma IgE level in adult.