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The universal formulae for λ(χreal, Eg, T) and λ(χreal, Eg, T)p of insulator having less impurities are experimentally proved, where λ(χreal, Eg, T) is the mean escape depth at Kelvin temperature T of secondary electrons emitted from insulators with band gap Eg and efficient electron affinity χreal, λ(χreal, Eg, T)p is the λ(χreal, Eg, T) due to electron-lattice interaction. Based on the mechanism of electron-insulator interaction, experimental data, existing formulae, ESTAR program and formulae for λ(χreal, Eg, T) and λ(χreal, Eg, T)p of insulator having less impurities, the methods of obtaining λ(χreal, Eg, T)e-e, λ(χreal, Eg, T)e-defect and λ(χreal, Eg, T)i are presented, where λ(χreal, Eg, T)e-e is the λ(χreal, Eg, T) due to electron–electron interaction, λ(χreal, Eg, T)e-defect is the λ(χreal, Eg, T) due to electron–defect interaction, λ(χreal, Eg, T)i is the λ(χreal, Eg, T) due to electron-impurity interaction. The λ(χreal, Eg, T)p, λ(χreal, Eg, T)e-e, λ(χreal, Eg, T)e-defect and λ(χreal, Eg, T)i can provide corresponding information regarding electron-insulator interaction. Thus, it can be concluded that the method of investigating electron-insulator interaction by secondary electron emission SEE is successfully presented in this work. According to experimental data, formula for λ(χreal, Eg, T), ESTAR program, calculated parameters of primary range and existing formulae for SEE, the method of calculating the ẟ at different T and in the range of 1.0 keV ≤ Epo ≤ 100.0 keV from insulator having less impurities is successfully presented, where ẟ is secondary electron yield, Epo is incident energy of primary electron.

Femtosecond time-resolved pump-probe technology has been widely used in studying ultrafast dynamics in various materials. In the present study a Co thin film on MgO, as a typical ferromagnetic material, was selected for investigating the ultrafast energy relaxation dynamics related to spin feature of materials. The energy relaxation dynamics of this thin film was measured by femtosecond transient absorption. The results can be well stimulated by a three-temperature model, in which electron, spin and lattice were involved, indicating that spin plays an important role in the energy relaxation. From this model, the hot electron temperature from the transient absorption under different pumping laser energy was calibrated which can reach 638, 724, 841 and 935 K with the energy of 3.2, 4.3, 6.0 and 7.5 J/m2 respectively. In additional, three time constants were obtained by a global analysis of the transient absorption, and attributed to electron–spin (250 ∼ 350 fs), electron–lattice (10 ∼ 20 ps), and spin–lattice interaction (300 ∼ 400 ps), respectively. By analyzing the dynamics of the ferromagnetic material after laser excitation, the rich physics governing ultrafast energy relaxation dynamics are elucidated, and the temperature references for femtosecond laser manipulation of this material are provided. [ABSTRACT FROM AUTHOR]

Featured Applications: Ultra-fast optical communication, optical memory, photo-switch. Over the past two decades (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene), which exhibits a metal–insulator (M–I) phase transition with charge–ordering (CO), has been investigated energetically because of attractive characteristics that include ultrafast and massive photoinduced spectral and structural changes. In contrast, while its crystal structure has much in common with the (EDO-TTF)2PF6 crystal, the organic alloy system of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 (MeEDO-TTF = 4,5-ethylenedioxy-4′-methyltetrathiafulvalene) exhibits a quite different type of M–I phase transition that is attributed to Peierls instability. Here, an optical study of the static absorption spectra and the time-resolved changes in the absorption spectra of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 are reported. The observed absorption spectra related to the electronic structure are highly anisotropic. With a reduction in temperature (T), the opening of a small optical gap and a small shift in the center frequency of the C=C stretching mode are observed along with the M–I phase transition. Additionally, photoinduced transient states have been assigned based on their relaxation processes and transient intramolecular vibrational spectra. Reflecting small valence and structural changes and weak donor–anion interactions, a photoinduced transient state that is similar to the thermal-equilibrium high-T metallic phase appears more rapidly in the alloy system than that in (EDO-TTF)2PF6. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates an effect of a target temperature on lattice excitation by the relaxing electron ensemble in a swift heavy ion track. A new version of the Monte-Carlo code TREKIS is used for this purpose. Cross sections implemented in TREKIS are constructed within the dynamic structure factor/complex dielectric function (DSF-CDF) formalism. This enables us to take into account unusual pathways of collective responses of the electronic and ionic subsystems to their femtosecond excitations in SHI tracks. The paper demonstrates that the temperature dependent fundamental asymmetry of the lattice DSF manifests itself in different kinetics of energy exchange between the electronic and atomic systems of alumina in SHI tracks at different temperatures (80 K vs. 300 K). [ABSTRACT FROM AUTHOR]

In the last years the Mn 4+ has been successfully used as a dopant in the red-emitting phosphors based on fluoride matrices such as: AMF 6 (A=Na, K, Cs, Ba, Rb; M=Si, Ti, Ge), due to its efficient red emission around 630 nm. The peculiarities of the Mn 4+ emission are the consequence of the specific energetic structure related to three electrons occupying the 3 d orbitals which interact with the crystal field of the lattice. The 3 d 3 ion system is one of the most extensively investigated systems, specifically concerning the Cr 3+ , since Al 2 O 3 :Cr 3+ (ruby) has been used for laser generation. In this contribution the details of energetic structure and kinetics of radiative and nonradiative processes in the 3 d 3 system are discussed. Special attention is given to consideration of the electron-lattice interaction and spin-orbit coupling. Differences between the spectroscopic properties of Cr 3+ and Mn 4+ ions in different lattices are analyzed in the framework of the extended crystal field model that includes the vibronic structure of the system. Specifically, we present the proper formula describing the temperature dependence of the Mn 4+ luminescence lifetime that includes the interaction with odd-parity phonons. [ABSTRACT FROM AUTHOR]

Over the past two decades (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene), which exhibits a metal–insulator (M–I) phase transition with charge–ordering (CO), has been investigated energetically because of attractive characteristics that include ultrafast and massive photoinduced spectral and structural changes. In contrast, while its crystal structure has much in common with the (EDO-TTF)2PF6 crystal, the organic alloy system of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 (MeEDO-TTF = 4,5-ethylenedioxy-4′-methyltetrathiafulvalene) exhibits a quite different type of M–I phase transition that is attributed to Peierls instability. Here, an optical study of the static absorption spectra and the time-resolved changes in the absorption spectra of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 are reported. The observed absorption spectra related to the electronic structure are highly anisotropic. With a reduction in temperature (T), the opening of a small optical gap and a small shift in the center frequency of the C=C stretching mode are observed along with the M–I phase transition. Additionally, photoinduced transient states have been assigned based on their relaxation processes and transient intramolecular vibrational spectra. Reflecting small valence and structural changes and weak donor–anion interactions, a photoinduced transient state that is similar to the thermal-equilibrium high-T metallic phase appears more rapidly in the alloy system than that in (EDO-TTF)2PF6.

The dynamic collision of an on-chain same charged polaron pair with an off-chain counterion trapped in an impurity molecule, under the influence of an external electric field, has been investigated using a nonadiabatic evolution method. We demonstrate that the bipolaron, the exciton and the trion are the main products in such a reaction, and that the trion can be formed by both the direct recombination of a positive polaron pair with a counterion and the secondary recombination of the formed bipolaron with either a trapped polaron, a charged defect, or an impurity of the opposite sign, which is consistent with the experimental evidence qualitatively. Meanwhile, our results show that the strength of the applied electric field and the impurity potential play important roles in the polaron pair-impurity collision. These results are expected to be helpful to understand the electroluminescence and conductivity in conjugated polymers. [ABSTRACT FROM AUTHOR]

In this letter, it is proposed that the impact ionization in amorphous Se films, which triggers avalanche carrier multiplications, occurs through transformations of electron and hole motions from polaronic to supersonic states, the situation resembling those envisaged for semiconducting one-dimensional organic polymers. However, reflecting unique origins of the conduction and the valence band in Se, the electron-lattice interaction appears stronger than the hole-lattice interaction, which seems to be responsible for characteristic properties such as less efficient electron multiplication. The idea is consistent with the fact that a-Si:H having three-dimensional structures exhibits no corresponding phenomena. [ABSTRACT FROM AUTHOR]

Abstract: The phosphors of Sb3+ and Eu3+ activated YBO3 were synthesized via solid-state reaction. The crystal structure was investigated using X-ray diffraction analysis. The luminescence and energy transfer were investigated on the synchrotron radiation instrument, by exciting with different wavelengths at room temperature or as low temperature as 14K. The electron–lattice interaction between the activator Sb3+ and the host of YBO3 combined with the spin–orbit interaction of Sb3+ result in a large Stokes shift in Sb3+ emission, giving rise to no matchable energy levels for the energy transfer from Sb3+ to Eu3+. Nevertheless, the excitation energy could transfer from Bi3+ to Eu3+, which has the same ns2 electronic configuration as Sb3+. Taking advantage of the simultaneous isolated luminescence of Sb3+ and Eu3+, finally, the white luminescence from a single phosphor was tuned up by tailoring Sb3+ and Eu3+ concentrations in the YBO3 host, which shows potential application in deep ultraviolet light-emitting diodes (LEDs). [Copyright &y& Elsevier]

Abstract: Within a Su–Schrieffer–Heeger model modified to include an external electric field, the dynamical process of oppositely charged polarons in a polymer chain is simulated by using a non-adiabatic evolution method. It is found that the polaron pair can combine with neutral exciton in the presence of a weak electric field, and the field requirement for achieving exciton is very strict in a pure polymer chain. But under the assistance of impurities, the exciton can be produced under a wide range of applied field strengths. The yield of neutral exciton can reach as high as 96%, which is significant for electroluminescent efficiency of OLEDs. [Copyright &y& Elsevier]

Abstract: The phosphor of YBO3: Sb3+ was synthesized by solid state reaction. Its crystal structure was examined by using X-ray diffraction analysis. The morphology and particle size were characterized with a scanning electron microscopy. The properties of YBO3: Sb3+ luminescence was systematically studied by exciting borate host, the 1P1 and 3P1 levels of Sb3+ at the Ci and C 1 sites with 168, 203, 218, 252 and 262nm, respectively, measured on the synchrotron radiation instruments. The different configurations of emission spectra excited with variant wavelengths show the character of wavelength-selective excitation, which was attributed to different occupations of the Sb3+ site in the YBO3 crystal lattice. Moreover, strong electron–lattice interaction (i.e., the Jahn–Teller effect) between Sb3+ and YBO3 host was discriminated by comparing low temperature and room temperature spectra. The site-selective luminescence was confirmed by YBO3 activated with multiple Sb3+ concentrations. The spectral assignment was verified with fluorescence lifetime achieved by using the Time-Correlated Single-Photon Counting method. [Copyright &y& Elsevier]

Abstract: In this study we demonstrate that the electron–lattice interaction (ELI) could be controlled by changing exciton delocalization length in ordered organic nanoclusters called J-aggregates. Particularly it could be done via the J-aggregates solvate shell manipulation using surfactants. The strong correlation between the J-aggregates luminescence quantum yield and the ELI strength has been reviled that allows us to consider the exciton self-trapping as the main mechanism of the J-aggregates luminescence losses. [Copyright &y& Elsevier]

Abstract: The dynamic formation process of a trion by recombination of an on-chain bipolaron with an off-chain counterion trapped in a radical molecule, under the influence of an external electric field, has been investigated using a nonadiabatic evolution method. We demonstrate that the dynamic formation of the trion depends sensitively on the strength of the applied electric field, the radical potential, and the coupling between the polymer chain and radical. The trion can be formed efficiently via the bipolaron-trapped counterion reaction under the appropriate conditions. Our simulation provides theoretical evidence for the trion formation channel proposed by Kadashchuk et al. The bipolaron-trapped counterion reaction also makes an additional contribution to electroluminescence in conjugated polymers that lies beyond the set of processes involving polaron recombination. [Copyright &y& Elsevier]

Abstract: Based on the Su–Schrieffer–Heeger model and the nonequilibrium Green’s function formalism, we have investigated charge transportation in a metal/polythiophene/metal structure. Results for the simulated conductivity include I–V curves that show an abrupt onset of negative differential resistance (NDR) with a peak-to-valley current ratio as high as 70. Combining these results with an analysis of the configuration of the molecular lattice and the reduced eigenvalues, it was found that the NDR mechanism was largely attributable to structural changes in the organic layer induced by the bias voltage. These results can help in understanding the electron–lattice coupling effect and the origin of NDR behavior in the I–V characteristics of organic molecular devices. [Copyright &y& Elsevier]

Single-crystal diffraction studies have been conducted up to 50 GPa using synchrotron radiation with diamond anvil cells. Electron density distribution (EDD) analysis has been performed by the maximum entropy method (MEM) using single-crystal diffraction intensity data in order to elucidate the electric conductivity change, electronic state, charge transfer and charge disproportionation with changing pressure. The MEM calculation based on Fobs(h k l) shows a much more precise EDD than the difference Fourier synthesis based on Fobs(h k l)-Fcalc(h k l). The radial distribution of the density indicates the enhancement of the electron localization with increasing pressure. The anisotropy in the electric conductivity of FeTiO3 ilmenite has been clarified by the EDD analysis. The MEM analyses clarify the structure transition from the cubic to tetragonal structure of Fe2TiO4 ulvospinel. The Jahn-Teller distortion is induced from Fe2+ (3d6) at the tetrahedral site at low temperature and high pressure (HP). The electron density analyses at HPs also elucidate the structure changes of KNbO3, PbTiO3 and BaTiO3 ferroelectrics. The static dipole moment can be evaluated by the observed effects and deformation of the site symmetry. [ABSTRACT FROM AUTHOR]

Abstract: In a two orbital model, we formulate Jahn–Teller coupled charge density wave in one electron per lattice site limit. Softening of Jahn–Teller phonons corresponding to distortion modes or associated with perfect nesting of Fermi surface leads to this instability at low temperature. The gap equation for charge density wave state and its dependences on electron–lattice coupling are calculated explicitly when any one of the Jahn–Teller modes is excited cooperatively. We find that the distortion mode yields lowest free energy. Effect of electron–lattice interaction on collective mode, such as amplitude mode, is more pronounced when the excited mode is . [Copyright &y& Elsevier]

A mechanism of self-consistently induced one-dimensional singularities of electronic density of states (DOS) in cuprates is proposed. It is found that unidirectional dynamic confinement of electrons motion by quantum lattice vibrations (presumably, by B buckling mode) may cause transition into ordered electronic state possessing extended 'van Hove singularities' of Floquet modes. This finding may explain observed enhancement of the ordering instability in the anti-nodal regions of the 'Fermi surface' in the under- and optimally doped high- T cuprates. Also predicted is a destruction of the dynamic electron-lattice confinement effect in strong enough magnetic field that simultaneously maintains the electronic order. [ABSTRACT FROM AUTHOR]

Abstract: We have calculated conductance of armchair carbon nanotubes under lattice strain causing twisting deformation in the presence of impurities with interaction range larger than the lattice constant. Ballistic transport is realized without deformation, while the twisting deformation induces electron scattering due to the impurities so that the conductance is strongly suppressed showing Anderson localization. As a result, it is promising to control the electron conduction in metallic carbon nanotubes by external strain. [Copyright &y& Elsevier]

Abstract: Splitting of the first excited doublet state of ions in the crystals in external magnetic fields up to 5.5T has been studied using measurements of luminescence spectra at low temperatures. In the magnetic field perpendicular to the -symmetry axis of the crystal lattice, the splitting of the non-Kramers doublet is caused by the joint action of the nonlinear Zeeman effect and the piezospectroscopic effect related to parastriction. Experimental dependences of the doublet splitting on the magnetic field strength and direction are in good correspondence with the theoretical estimations obtained in the framework of the semiphenomenological crystal field model. It is shown that spectroscopic data present direct information on the forced magnetostriction in the basal plane of uniaxial Van Vleck paramagnets that contain non-Kramers rare earth ions. The measured concentration dependence of the doublet splitting can be explained by taking into account variations of the elastic constants with the concentration of ions. [Copyright &y& Elsevier]

This paper investigated the electron-solid interaction in insulator by secondary electron emission emitted from insulators. And the method of calculating the ẟ at different T and in the range of 1.0 keV≤ E po ≤100.0 keV from insulator having less impurities is successfully presented in this study. [Display omitted] • The universal formulae for λ (χ real , E g , T) and λ (χ real , E g , T) p of insulator having less impurities are experimentally proved. • Based on the mechanism of electron-insulator interaction, experimental data, existing formulae, ESTAR program and formulae for λ (χ real , E g , T) and λ (χ real , E g , T) p of insulator having less impurities, the methods of obtaining λ (χ real , E g , T) e-e , λ (χ real , E g , T) e-defect and λ (χ real , E g , T) i are presented. Thus, it can be concluded that the method of investigating electron-insulator interaction by SEE is successfully presented in this work. So this study advances the theoretical research of electron-insulator interaction. • According to experimental data, formula for λ (χ real , E g , T), ESTAR program, calculated parameters of primary range and existing formulae for SEE, the method of calculating the ẟ at different T and in the range of 1.0 keV ≤ E po ≤ 100.0 keV from insulator having less impurities is successfully presented. Therefore, this study advances the research of SEE. The universal formulae for λ (χ real , E g , T) and λ (χ real , E g , T) p of insulator having less impurities are experimentally proved, where λ (χ real , E g , T) is the mean escape depth at Kelvin temperature T of secondary electrons emitted from insulators with band gap E g and efficient electron affinity χ real , λ (χ real , E g , T) p is the λ (χ real , E g , T) due to electron-lattice interaction. Based on the mechanism of electron-insulator interaction, experimental data, existing formulae, ESTAR program and formulae for λ (χ real , E g , T) and λ (χ real , E g , T) p of insulator having less impurities, the methods of obtaining λ (χ real , E g , T) e-e , λ (χ real , E g , T) e-defect and λ (χ real , E g , T) i are presented, where λ (χ real , E g , T) e-e is the λ (χ real , E g , T) due to electron–electron interaction, λ (χ real , E g , T) e-defect is the λ (χ real , E g , T) due to electron–defect interaction, λ (χ real , E g , T) i is the λ (χ real , E g , T) due to electron-impurity interaction. The λ (χ real , E g , T) p , λ (χ real , E g , T) e-e , λ (χ real , E g , T) e-defect and λ (χ real , E g , T) i can provide corresponding information regarding electron-insulator interaction. Thus, it can be concluded that the method of investigating electron-insulator interaction by secondary electron emission SEE is successfully presented in this work. According to experimental data, formula for λ (χ real , E g , T), ESTAR program, calculated parameters of primary range and existing formulae for SEE, the method of calculating the ẟ at different T and in the range of 1.0 keV ≤ E po ≤ 100.0 keV from insulator having less impurities is successfully presented, where ẟ is secondary electron yield, E po is incident energy of primary electron. [ABSTRACT FROM AUTHOR]

Abstract: The sound velocity v s(T) has been investigated for La1− X Ca X MnO3 (0.46⩽X⩽0.50) in applied fields up to . The characteristic v s(T) softening and the subsequent hardening are observed below the ferromagnetic transition temperature T c. The gradual v s(T) softening above the charge-order (CO) transition temperature T CO and the v s(T) hardening just below T CO are also observable. The v s(T) softening above T CO is at first enhanced and then reduced with increasing applied field. These results can be understood on the basis of the enhanced spin–lattice and charge–lattice interaction. [Copyright &y& Elsevier]

Abstract: Ultrafast charge dynamics in one-dimensional Mott insulators was investigated by femtosecond reflection spectroscopy on organic molecular compounds, K-tetracyanoquinodimethane (TCNQ), Rb-TCNQ, and bis(ethylenedithio)tetrathiafulvalene (ET)-difluorotetracyanoquinodimethane (F2TCNQ). In K- and Rb-TCNQ, photocarriers are localized as polarons with ∼70fs and recombine with a few ps. In ET-F2TCNQ, photocarriers lead to a metallic state and decay with ∼200fs. Such differences of the charge dynamics can be explained by taking account of the different magnitudes of the electron-lattice interactions in the three compounds. [Copyright &y& Elsevier]