Electronic Transitions Research Articles

Molten flux growth of single crystals of quasi-1D hexagonal chalcogenide BaTiS3

BaTiS3, a quasi-1D complex chalcogenide, has gathered considerable scientific and technological interest due to its giant optical anisotropy and electronic phase transitions. However, the synthesis of high-quality BaTiS3 crystals, particularly those featuring crystal sizes of millimeters or larger, remains a challenge. Here, we investigate the growth of BaTiS3 crystals utilizing a molten salt flux of either potassium iodide, or a mixture of barium chloride and barium iodide. The crystals obtained through this method exhibit a substantial increase in volume compared to those synthesized via the chemical vapor transport method, while preserving their intrinsic optical and electronic properties. Our flux growth method provides a promising route toward the production of high-quality, large-scale single crystals of BaTiS3, which will greatly facilitate advanced characterizations of BaTiS3 and its practical applications that require large crystal dimensions. Additionally, our approach offers an alternative synthetic route for other emerging complex chalcogenides.Graphical

Chiral quantum heating and cooling with an optically controlled ion

Quantum heat engines and refrigerators are open quantum systems, whose dynamics can be well understood using a non-Hermitian formalism. A prominent feature of non-Hermiticity is the existence of exceptional points (EPs), which has no counterpart in closed quantum systems. It has been shown in classical systems that dynamical encirclement in the vicinity of an EP, whether the loop includes the EP or not, could lead to chiral mode conversion. Here, we show that this is valid also for quantum systems when dynamical encircling is performed in the vicinity of their Liouvillian EPs (LEPs), which include the effects of quantum jumps and associated noise—an important quantum feature not present in previous works. We demonstrate, using a Paul-trapped ultracold ion, the first chiral quantum heating and refrigeration by dynamically encircling a closed loop in the vicinity of an LEP. We witness the cycling direction to be associated with the chirality and heat release (absorption) of the quantum heat engine (quantum refrigerator). Our experiments have revealed that not only the adiabaticity breakdown but also the Landau–Zener–Stückelberg process play an essential role during dynamic encircling, resulting in chiral thermodynamic cycles. Our observations contribute to further understanding of chiral and topological features in non-Hermitian systems and pave a way to exploring the relation between chirality and quantum thermodynamics.

Ultra‐Broadband Near‐Infrared Luminescence from a Vanadium‐Activated Phosphate Glass

AbstractBroadband near‐infrared (NIR) emitting materials have gained considerable attention for their applications in lighting, displays, sensing, bio‐imaging, and optical amplification. Recently, numerous excellent broadband NIR emitting materials are developed by introducing Cr3+, Bi+, or Ni2+ ions to various hosts. However, there is a notable absence of reports on ultra‐broadband NIR emitters spanning the entire telecommunication window as well as the NIR‐I (700–1000 nm) and NIR‐II (1000–1700 nm) biological windows activated by vanadium ions. Herein, the study presents, for the first time to the best of the knowledge, ultra‐broadband NIR emission ranging from 850 to 1600 nm (peaking at ≈1000 nm) at room temperature in vanadium‐doped phosphate glass. Detailed spectra and microscopic structure analysis reveal that two V3+‐emitting centers predominantly contribute to the ultra‐broadband emission, corresponding to 3T2(3F)→3A2(3F) spin‐allowed and 3T2(3F)→1E(1D) spin‐forbidden electron transitions of tetrahedrally coordinated V3+ ions. Notably, the tunability of NIR emission peak is demonstrated by adjusting the local glass structure or the vanadium doping content. Moreover, glass‐converted light‐emitting diodes (gc‐LEDs) are fabricated from vanadium‐doped glass, and the potential applications are demonstrated. The work opens new avenues for the design and fabrication of broadband NIR‐emitting materials and opto‐electronic devices.

Nuclear deformation effects in the spectra of highly charged ions

With the increasing precision of spectroscopic measurements, there is a growing demand for more accurate theoretical predictions, which requires the estimation of various higher-order effects, such as the nuclear deformation effect. Here, we present the results for nuclear deformation correction for the widest range of nuclei. The effects are investigated in terms of electronic transition energies, g factors, and hyperfine splitting constants, by implementing the deformed Fermi nuclear model to the Dirac equation. Based on the improved methodology and appropriate data classification, we present the results for over 1100 nuclei on figures, showing the general trends and anomalies. Moreover, it can serve as a simple tool providing estimations for specific planned research. In addition, we examine the connections and significance of deformation effects in the search of new physics with singly charged ions. Published by the American Physical Society 2024

Tb3+‐Doped Ca3Ga4O9 Phosphors with Color‐Tunable Photoluminescence and Non‐Pre‐Irradiation Mechanoluminescence for Multimodal Applications

AbstractMaterials that can emit light under optical/mechanical stimulation are usually called photoluminescent/mechanoluminescent (PL/ML) materials. PL materials are used in diverse fields for half a century. While, ML materials have burst out in the last two decades, and now are showing great application potential in the fields of anti‐counterfeiting, information storage, and stress imaging. It is of great significance to explore new luminescent materials with PL and ML dual response. In this study, Tb3+‐doped Ca3Ga4O9 phosphors with color‐tunable PL and non‐pre‐irradiation ML properties are reported. Ca3Ga4O9 exhibits a broadband blue emission centering at 425 nm, which originates from the 4T2‐4A2 transition of electrons in d orbits of Ga3+. Due to the energy transfer from host to Tb3+, color‐tunable emission from blue to cyan, and ultimately to green can be realized by increasing the concentration of Tb3+. Particularly, ML is seen from Ca3Ga4O9:Tb3+ under grinding and from the Ca3Ga4O9:Tb3+/PDMS film under bending or stretching originated from the triboelectric mechanism. The non‐pre‐irradiation ML behavior is evidenced by the contrast thermoluminescence (TL) experiments. This study not only provides a new candidate toward multi‐purpose luminescent applications, but also demonstrates a good case in which the triboelectric effect can efficiently trigger the non‐pre‐irradiation ML behavior.

New insights into the bonding, electronic and optical properties of fergusonite and scheelite ReNbO4 (Re = Y, La and Lu) compounds

A systematic study of the structural, bonding, electronic, and optical properties of the ReNbO4 (Re = Y, La, and Lu) compounds with the fergusonite (space group I/2a) and scheelite (space group I41/a) structure was performed using density functional theory calculations. The aim of these calculations was to resolve some doubt about these properties for the fergusonite phase and to fill the existing knowledge gap for the scheelite phase. To carry out geometry optimization, the generalized gradient approximation for solids was used. Based on these optimized crystal structures, the bonding, electronic and optical properties were determined using the modified Becke and Johnson exchange potential. An analysis of the bonds between Nb and O atoms showed that Nb atoms in the fergusonite structure of the rare-earth niobates were octahedrally coordinated to oxygen atoms, unlike in the scheelite phase, which had tetrahedral coordination. The calculated values of the direct energy band gap for the fergusonite YNbO4, LaNbO4 and LuNbO4 compounds were 4.435, 4.427 and 4.431 eV, respectively. The optical spectrum for these systems is characterized by a small exciton binding energy, which affects the experimental prediction of the energy band gap when the Tauc plot method is used. The values for the energy band gap in the scheelite phase were 4.625 eV for YNbO4, 4.844 eV for LaNbO4 and 4.611 eV for LuNbO4 and all were indirect. The real and imaginary parts of the dielectric tensor were computed up to 25 eV for both phases, and were interpreted based on their electronic structure. The lower energy regions of the optical spectra of these systems are mainly due to electronic transitions within the NbO6 polyhedron (for the fergusonite phase) and the NbO4 polyhedron (for the scheelite phase), i.e., electronic transitions from the occupied O-2p states at the top of the valence band to the unoccupied Nb-4d states at the bottom of the conduction band.

A 1750nm thulium-doped optical fiber laser design: Theoretical model and code simulation

This article mainly studies the physical model design and code simulation of a thulium-doped fiber laser that outputs 1750nm laser. The optical fiber laser has been widely used due to its excellent performance compared with other solid-state laser devices. Among all types of fiber lasers, ytterbium-doped fiber lasers possess the highest output power, whereas they seem to be impractical when an output laser with a longer wavelength is required. However, Thulium-doped lasers have huge room for development to solve the problem, whose unique center wavelength characteristics provide them with huge utilization value. This article shows the electronic transition process a of thulium-doped laser and the power transmission diagram in the fiber. Its rate equation and power equation are also listed below. Through paper retrieval and data extraction, the values of laser parameters can be accurately confirmed, and its power curve can also be obtained through simulation. After analyzing the data obtained from the simulation, the working principle of the fiber laser was intuitively displayed, and the performance of the system was further evaluated. Last but not least, several limitations of this experiment will also be discussed, in order to explore the system more thoroughly.

Investigation of structural and optoelectronic integrity of Sm3+ doped CaWO4 for LED applications

In this study we illustrate the structural, electronic and optical integrity of Ca1-xSm(2/3)xWO4 (x = 0.00, 0.02, 0.04, 0.06 and 0.08) crystals for optoelectronic applications via experimental and first principles approach. According to our experimental outcomes, CaWO4 crystallizes in scheelite type tetragonal structure devoid of impurity which depends on the A-site cationic radius and dopant-host compatibility. As a result, the dopant induced lattice distortion occur due to symmetric and asymmetric stretching of (Ca, Sm)—O and W–O bonds within [CaO8] and [WO4] cluster. According to our FT-IR and Raman spectral analysis, the non-centrosymmetric vibration within the [WO4]2- complex gives rise to internal modes while the Ca2+/Sm3+ cationic displacement and rigid molecular ionic group constitutes the external modes which equally impacts the electronic and optical characteristics of the host material. While the forbidden gap extends due to Sm3+ substitution, the delocalization of W-5d orbitals on the other hand occur due to rising distortions within the WO4 cluster. As a result, the polarization between [WO4] and [CaO8] cluster and difference in the electronic transitions controls the optical characteristics of the host material. According to our experimental and theoretical predictions, a noticeable decrease in the optical band gap (5.96–5.83 eV) occurs due to heterovalent cationic substitution (Sm3+), difference in structural order-disorder and charge carrier density. As a result, a broad photoluminescence (PL) spectrum among acceptor doped samples verifies the impact of multi-phonon or multi-level processes on the luminosity of the host material.

Application of entertainment e-learning mode based on genetic algorithm and facial emotion recognition in environmental art and design courses

This article is based on facial recognition and further designs an entertainment electronic learning mode. Facial emotion recognition may be affected by light, angle, and expression. In order to improve recognition accuracy and stability, distortion adjustment techniques were used to process facial images, ensuring that the model can accurately capture and recognize the features of facial expressions. The study applies online facial emotion recognition to entertainment electronic learning modes, where learners interact with the system. The system can detect and recognize learners’ facial expressions in real-time, and provide corresponding feedback and learning resources based on different expressions. By collecting and analyzing experimental data, evaluate the practicality of the model and the level of acceptance and satisfaction of learners towards the model. The entertainment electronic learning mode based on facial recognition provides an innovative learning approach by constructing a pattern architecture, distortion adjustment, and applying online facial emotion recognition. By optimizing the positioning and integrating the entertainment electronic learning mode with environmental art and design courses, we aim to enhance students’ learning motivation and interest. Develop optimization strategies to enhance students’ comprehensive abilities in the field of environmental art and design.

Academic ESP Courses in a Hybrid Mode: Attitudes and Perceptions

Developing academic ESP courses in a hybrid mode has come to the forefront of the educational agenda due to social and economic reasons: technological advance followed by the emergence of new communication, business and education technologies; new generations of learners who grow up in virtual reality rather than in real life; commercialisation of education; changes in workplaces and business organisations; a pandemic that resulted in increased use of the electronic and hybrid modes of interacting and working. In light of these circumstances, the research on the key actors in the educational process – learners and teachers – has gained importance and has become the reason to initiate a study of these actors’ attitudes and perceptions with regard to the academic ESP courses in a hybrid mode. The article presents and discusses the results from a survey conducted within this study and related to the preparation of reference criteria for course design in terms of parameters. Data analysis has implications for the educational sector in terms of language and subject course development, as well as of the introduction of relevant policies in higher education.

Optical band gap engineering and comparison of conductivity of CaTiO3 and LiNbO3 doped PVDF films

This study explores the impact of CaTiO3 and LiNbO3 crystals on the optical and dielectric properties of polyvinylidene fluoride (PVDF) films. Our investigation employs UV–Visible Spectroscopy to characterize the n-π* C-F related electronic transition within the PVDF matrix. We find that CaTiO3 crystals significantly decrease the composite’s band gap and dielectric properties, enhancing its electronic and optical attributes. Conversely, LiNbO3 crystals increase the band gap energy. These variations align with observed DC conductivity changes, suggesting novel functionalities for optoelectronic, sensing, and energy storage applications.

Practical Trainable Temporal Postprocessor for Multistate Quantum Measurement

We develop and demonstrate a trainable temporal postprocessor (TPP) harnessing a simple but versatile machine learning algorithm to provide optimal processing of quantum measurement data subject to arbitrary noise processes for the readout of an arbitrary number of quantum states. We demonstrate the TPP on the essential task of qubit state readout, which has historically relied on temporal processing via matched filters in spite of their applicability for only specific noise conditions. Our results show that the TPP can reliably outperform standard filtering approaches under complex readout conditions, such as high-power readout. Using simulations of quantum measurement noise sources, we show that this advantage relies on the TPP’s ability to learn optimal linear filters that account for general quantum noise correlations in data, such as those due to quantum jumps, or correlated noise added by a phase-preserving quantum amplifier. Furthermore, we derive an exact analytic form for the optimal TPP weights: this positions the TPP as a linearly scaling generalization of matched filtering, valid for an arbitrary number of states under the most general readout noise conditions, all while preserving a training complexity that is essentially negligible in comparison with that of training neural networks for processing temporal quantum measurement data. The TPP can be autonomously and reliably trained on measurement data and requires only linear operations, making it ideal for field-programmable gate array implementations in circuit QED for real-time processing of measurement data from general quantum systems. Published by the American Physical Society 2024

Blue Phosphorescent Pt(II) Compound Based on Tetradentate Carbazole/2,3'-Bipyridine Ligand and Its Application in Organic Light-Emitting Diodes.

The tetradentate ligand, merging a carbazole unit with high triplet energy and dimethoxy bipyridine, renowned for its exceptional quantum efficiency in coordination with metals like Pt, is expected to demonstrate remarkable luminescent properties. However, instances of tetradentate ligands such as bipyridine-based pyridylcarbazole derivatives remain exceptionally scarce in the current literature. In this study, we developed a tetradentate ligand based on carbazole and 2,3'-bipyridine and successfully complexed it with Pt(II) ions. This novel compound (1) serves as a sky-blue phosphorescent material for use in light-emitting diodes. Based on single-crystal X-ray analysis, compound 1 has a distorted square-planar geometry with a 5/6/6 backbone around the Pt(II) core. Bright sky-blue emissions were observed at 488 and 516 nm with photoluminescent quantum yields of 34% and a luminescent lifetime of 2.6 μs. TD-DFT calculations for 1 revealed that the electronic transition was mostly attributed to the ligand-centered (LC) charge transfer transition with a small contribution from the metal-to-ligand charge transfer transition (MLCT, ~14%). A phosphorescent organic light-emitting device was successfully fabricated using this material as a dopant, along with 3'-di(9H-carbazol-9-yl)-1,1'-biphenyl (mCBP) and 9-(3'-carbazol-9-yl-5-cyano-biphenyl-3-yl)-9H-carbazole-3-carbonitrile (CNmCBPCN) as mixed hosts. A maximum quantum efficiency of 5.2% and a current efficiency of 15.5 cd/A were obtained at a doping level of 5%.

B2O3+SiO2+BaO+Sm2O3+Na2O+MoO3 glasses: Preparation, optical, physical characteristics as well as γ-ray absorption ability

Samples of borosilicate glasses reinforced with various moles of MoO3 with general chemical formula (52-X)B2O3+13SiO2+19.75BaO+ 0.25Sm2O3+15Na2O+XMoO3: (0.0 (BSMO-0.0) ≤ X ≤ 10.0 (BSMO-10.0) mol%) were prepared using the melt-quenching technique. The physical, optical absorption, electronic transitions, and linear/nonlinear optical properties as well as γ-ray absorption capacity has been investigated. Density (ρ) of the BSMO-X glasses enhanced from 2.83 g cm−3 to 3.16 g cm−3. Molar volume (Vm) gradually decreased from 29.81 cm3/mol to 29.10 cm3/mol as MoO3 concentration increased from 0.0 to 10.0 mol% in the glass network. The BSMO-X glass samples exhibit absorption peaks at wavelengths of 402, 476, 936, 1072, 1227, 1368, 1469, 1527, and 1944 nm which associated with the electronic transitions originating from the lowest energy state (6H5/2) to 6P3/2, 4I11/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6H13/2 states, respectively. The indirect optical energy gap (Eg) changed from 3.15 eV to 2.82 eV, while the linear refractive index (no) increased from 2.37 to 2.44. Mass- (MAC) and linear- (LAC) absorption coefficients increased as MoO3content increased in the glass network. The BSMO-10.0 possessed the lowest values of half-value (HVL) layer among all investigated samples. The BSMO-X glasses achieve higher capability in radiation shielding than some standard concrete and glasses.

Effects of measurement power on state discrimination and dynamics in a circuit-QED experiment

We explore the effects of driving a cavity at a large photon number in a circuit-QED experiment where the “matterlike” part corresponds to a unique Andreev level in a superconducting weak link. The three many-body states of the weak link, corresponding to the occupation of the Andreev level by 0, 1, or 2 quasiparticles, lead to different cavity frequency shifts. We show how the nonlinearity inherited by the cavity from its coupling to the weak link affects the state discrimination and the photon number calibration. Both effects require treating the evolution of the driven system beyond the dispersive limit. In addition, we observe how transition rates between the circuit states (quantum and parity jumps) are affected by the microwave power, and compare the measurements with a theory accounting for the “dressing” of the Andreev states by the cavity. Published by the American Physical Society 2024

Zigzag phase transition of electrons confined within a thin annulus region

We consider a semiclassical approach to study the possible stabilization of a zigzag phase for a system of interacting electrons confined within a thin annulus region with infinite inner/outer walls. The electrons are considered spinless and interact via the standard Coulomb interaction potential. The classical minimum energy configuration of the system due to the Coulomb repulsion between electrons is accurately determined by using the simulated annealing method. As the number of electrons increases we see the appearance and stabilization of a two-ring structure with zigzag patterns. Further increase of the number of electrons appears to eventually lead to the collapse of the two-ring zigzag structure. A simple quantum treatment of the nodal features of the free many-particle wave function shows the appearance of nodal domain patterns that are consistent with the zigzag features that were observed in the classical model.

Influence of Eu, Gd and Lu dopants on the properties of TiO2: A first-principles study

The present study investigates the electronic structure, magnetic properties, and optical performance of anatase TiO2 and pure TiO2 systems with the addition of rare earth elements RE (Eu/Gd/Lu). Using first-principles calculations based on density-functional theory, we explore the effects of RE doping on these systems. Our calculations reveal that the structural stability remains intact under the conditions of RE doping. The total magnetic moment is determined to be 2.987 μB, 6.052 μB, and 0 μB for Eu, Gd, and Lu-doped TiO2 respectively. Furthermore, the band gap of Eu/Gd/Lu-doped TiO2 decreases significantly to 1.91eV, 1.8eV, and 1.88eV, leading to a lower energy requirement for electron transition, as compared to the initial energy band gap of 2.31eV. The incorporation of rare earth elements also results in an increase in the number of valence and conduction band energy levels near the Fermi level, primarily influenced by orbital electrons in the 4f layer of the rare earth elements. Additionally, our findings demonstrate a remarkable shift towards the red region in the absorption spectrum of the Eu-TiO2 system, accompanied by a relatively long photocarrier lifetime. These characteristics suggest its potential as a photocatalyst with enhanced performance. Overall, this research provides valuable theoretical insights towards the development and synthesis of novel TiO2 photocatalysts.

Optical properties and antimicrobial of ionic chitosan-MgO-SiO2@ aminolsilane nanocomposites

This investigation involved synthesizing a nanocomposite heterostructure, Chitosan-MgO-SiO2@aminosilane, using the physical blending of chitosan-MgO-silica with aminosilane using the sol–gel technique. The prepared nanocomposites were characterized using x-ray diffraction (XRD), Scanning/Transmission Electron Microscope (SEM-EDX/TEM), Fourier Transform Infrared Spectroscopy (FTIR), and optical analysis to investigate the microstructural and spectroscopic properties. XRD results confirmed the formation of orthorhombic Mg2SiO4 within the fabricated system. FTIR analysis verified interactions among chitosan, MgO-silica, and aminosilane, leading to the development of diverse functional groups, including M-O bonds, silanol-hydroxyl ions, and heteropolymeric-O-M within the chitosan-MgO-SiO2@aminosilane nanocomposite. Optical studies demonstrated that aminosilane-incorporated samples have two distinct absorption bands around 215 nm and 419 nm, corresponding to the electronic transitions π–π* (k-band) and n–π* (R-band), respectively. The absorption band at 400 nm is ascribed to localized surface plasmon resonance (SPR). The incorporation of aminosilane resulted in a decrease in the direct transition energy gap from 2.677 to 2.399 eV. The nanocomposites displayed significant antimicrobial activity against pathogenic microorganisms such as Gram-positive Staphylococcus aureus, Gram-negative Pseudomonas aeruginosa, and pathogenic fungi Candida albicans and Aspergillus niger. The positive antimicrobial response of the fabricated nanocomposites candidates them for various applications, including wound dressings and food packaging.

Synthesis and optoelectronic properties of bis-BODIPY-meso-phenyleneethynylene dimers

Three different bis-BODIPY-meso-phenyleneethynylene dimers were prepared in a straightforward manner following a sequence Liebeskind-Srogl- Stille cross-couplings, which allowed us to control the architecture of the final products. The phenyleneethynylene (PE) bridged bis-meso-BODIPYs, indistinctly of the ortho, meta or para substitution exhibit in dichloromethane, a main excitonic (S0–S1 electronic transition) peak at 503 ± 1 nm, similar to that of the monomer meso-phenyl BODIPY, evidencing the poor electronic communication between the two BODIPYs. This is supported by theoretical study where modest energy splitting of the S0–S1 electronic transition was found and by voltammetry where voltammograms of para and meta dimers show similar redox process to that of the monomer. The fluorescence spectra are also quite similar, but the ortho dimer presents two emission bands. The fluorescence quantum yield (φ) is much lower for para (0.6 %) and meta (2.9 %) dimers with respect to the monomer (4.3 %) and to the ortho homologous (15.1 %). This is likely due to non-radiative losses derived from the free rotation of the two BODIPYs in meso that is restricted in the ortho substitution. Intramolecular charge transfer (ICT) through photoinduced symmetry breaking can also occur in this latter dimer according to the Weller equation using the voltammetric oxidation/reduction potentials, and to the fluorescence quenching in polar solvents. Noncovalent interactions studies indicate significant π-π interactions in the excited state that could promote excimer formation. For which, the two emission bands in this compound could be also due to a monomer-like ICT state and excimers.

Synthesis of N2-Type Superatomic Molecules.

Exploration of multiple bonds between superatoms remains an uncharted territory. In this study, we present the synthesis and characterization of N2-type superatomic molecules featuring triple bonds between two superatoms. The successful synthesis of M2Au17 (M = Pd, Pt) nanoclusters hinged upon the photoinduced fusion of MAu12 superatoms, achieved through sequential electron transfer and detachment of [AuPR3]+ species. Solid-state structures were confirmed via X-ray crystallography, while their electronic structures were elucidated through density functional theory (DFT) calculations. Analysis of electronic absorption properties, coupled with time-dependent DFT calculations, unveiled a symmetry-dependent electron transition nature between superatomic molecular orbitals, akin to that observed in conventional molecules.