Anomalous Band Research Articles

Unveiling the charge density wave mechanism in vanadium-based Bi-layered kagome metals

The charge density wave (CDW), as a hallmark of vanadium-based kagome superconductor AV3Sb5 (A = K, Rb, Cs), has attracted intensive attention. However, the fundamental controversy regarding the underlying mechanism of CDW therein persists. Recently, the vanadium-based bi-layered kagome metal ScV6Sn6, reported to exhibit a long-range charge order below 94 K, has emerged as a promising candidate to further clarify this core issue. Here, employing micro-focusing angle-resolved photoemission spectroscopy (μ-ARPES) and first-principles calculations, we systematically studied the unique CDW order in vanadium-based bi-layered kagome metals by comparing ScV6Sn6 with its isostructural counterpart YV6Sn6, which lacks a CDW ground state. Combining ARPES data and the corresponding joint density of states (DOS), we suggest that the VHS nesting mechanism might be invalid in these materials. Besides, in ScV6Sn6, we identified multiple hybridization energy gaps resulting from CDW-induced band folding, along with an anomalous band dispersion, implying a potential electron-phonon coupling-driven mechanism underlying the formation of the CDW order. Our finding not only comprehensively maps the electronic structure of V-based bi-layer kagome metals but also provides constructive experimental evidence for the unique origin of CDW in this system.

Nonadiabatic Molecular Dynamics Simulations Provide Evidence for Coexistence of Planar and Nonplanar Intramolecular Charge Transfer Structures in Fluorazene.

Fluorazene is a model compound for photoinduced intramolecular charge transfer (ICT) between aromatic moieties. Despite intensive studies, both spectroscopic and theoretical, a complete model of its photophysics is still lacking. Especially controversial is the geometry of its ICT structure, or structures. In order to fill in the gaps in the state of knowledge on this important model system, in the present study I report the results of nonadiabatic molecular dynamics (NAMD) simulations of its photorelaxation process in acetonitrile solution. To afford a direct comparison to spectroscopic data, I use the simulation results as the basis for the calculation of the transient absorption (TA) spectrum. The NAMD simulations provide detailed information on the sequence of events during the excited-state relaxation of the title compound. Following initial photoexcitation into the bright S2 state, the molecule undergoes rapid internal conversion into the S1 state, leading to the locally excited (LE) structure. The LE structure, in turn, undergoes isomerization into a population of ICT structures, with geometries ranging from near-planar to markedly nonplanar. The LE → ICT isomerization reaction is accompanied by the decay of the characteristic excited-state absorption band of the LE structure near 2 eV. The anomalous fluorescence emission band of fluorazene is found to originate mainly from the near-planar ICT structures, in part because they dominate the overall population of ICT structures. Thus, the planar ICT (PICT) model appears to be the most appropriate description of the geometry of the ICT structure of fluorazene.

Retracted] LncRNA TUG1 serves an important role in hypoxia‑induced myocardial cell injury by regulating the miR‑145‑5p‑Binp3 axis.

Following the publication of this article, a concerned reader drew to the Editor's attention that, for several of the figures showing the results of Transwell migration and invasion assay experiments, unexpected areas of similarity were identified in terms of cellular patterns comparing among data panels where the results from differently performed experiments were intended to have been shown, although the areas immediately surrounding these areas often featured comparatively different distributions of cells. Moreover, several of the figures contained invasion/migration assay data that were strikingly similar to data that had appeared in articles published previously by different authors at different research institutes. In addition, the western blots in this article were presented with atypical, unusually shaped and possibly anomalous protein bands in many cases. After having conducted an internal investigation, the Editor of Molecular Medicine Reports has reached the conclusion that the potentially anomalous data in this paper were unlikely to have arisen by coincidence. Therefore, on the grounds of a lack of confidence in the integrity of these data, and given the fact that some of the data were strikingly similar to that which had been published previously in other articles and journals, the Editor has decided that the article should be retracted from the publication. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a reply. The Editor apologizes to the readership for any inconvenience caused, and thanks the concerned reader for drawing this matter to our attention. [Molecular Medicine Reports 42: 2422‑2430, 2018; DOI: 10.3892/mmr.2017.8116].

Origin of the Cr3+ concentration-dependent broadband near-infrared emission in Sc2Si2O7.

The challenge of developing phosphors with tailored near-infrared (NIR) emission ranges to meet the diverse demands of various applications is a paramount concern in the contemporary realm of NIR phosphor research. A strong dependence of NIR emission on Cr3+ concentration has been demonstrated in Sc2-xSi2O7:xCr3+, which exhibits an NIR emission band at 840 nm for low Cr3+ doping concentrations (x = 0.001-0.01) and an anomalous NIR emission band at 1300 nm for high Cr3+ doping concentrations (x = 0.01-0.10). Careful investigation of the crystal structure, excitation and emission spectra, and luminescence decay curves indicates that the two NIR emissions can be attributed to the isolated Cr3+ ions and the Cr3+-Cr3+ pairs, respectively. The strong interaction of exchange-coupled Cr3+-Cr3+ pairs is supported by temperature-dependent emission spectra, luminescence decay curves and electron paramagnetic resonance (EPR) measurements. This work provides a new insight into the study of Cr3+-Cr3+ pairs for broadband NIR emission.

Modulation of the intraseasonal variability in early summer precipitation in eastern China by the Quasi-Biennial Oscillation and the Madden–Julian Oscillation

Abstract. Using the reanalysis and multiple observations, the possible impact of the Madden–Julian Oscillation (MJO) on early summer (June–July) rainfall in eastern China and its modulation by the Quasi-Biennial Oscillation (QBO) are examined. The composite results show that the suppressed (enhanced) convection anomalies for MJO phases 8–1 (4–5) are more concentrated over the maritime continent and the western Pacific during easterly QBO (EQBO). As a consequence, more significant wet (dry) anomalies develop in South (eastern) China during MJO phases 8–1 (4–5) configured with easterly (westerly) QBO. The enhancement and expansion of the anomalous tropical convection band do not necessarily correspond to enhancement of the extratropical circulation response to MJO phases 8–1 (4–5) configured with westerly (easterly) QBO. The anomalous high (low) over the maritime continent and western Pacific associated with MJO phases 8–1 (4–5) is intensified (deepened) during easterly (westerly) QBO, leading to large southwesterly (northeasterly) anomalies in South China and the coasts, carrying abundant (sparse) moisture. Two anomalous meridional circulation cells are observed for MJO phases 8–1 in the East Asia sector, with downwelling anomalies around 5–20∘ N, upwelling anomalies around 20–30∘ N, and another downwelling branch northward of 30∘ N, which are enhanced during easterly QBO. The anomalous meridional circulation cells are reversed for MJO phases 4–5, which are stronger during westerly QBO with the anomalous downwelling and dry anomalies covering eastern China. The combined impact of MJO phases 8–1 and easterly QBO on the early summer rainfall is noticeable in 1996, 2016, and 2020. The enormous rainfall amount appeared along the Yangtze River in 1996, 2016, and 2020 due to the extended period of MJO phases 8–1 under the background of the easterly QBO.

Fine Detection and Analysis of Hidden Karst in Wellsite with Quasi-Three-Dimensional TDEM Based on Lateral Constraint

Considering that karst caves, underground rivers, and dissolution fractures in shallow carbonate formation in the Sichuan Basin are extremely developed, leakage, failure and plugging difficulties are easy to occur in the drilling process. The TDEM was used to carry out the exploration of hidden karst geological bodies in well QM2, and the quasi-three-dimensional inversion based on lateral constrain was used to invert the TDEM data. Three NW trending anomalous bands were identified in the lower Triassic Jialingjiang Formation within the range of drilling, consisting of seven relatively low-resistivity anomalous zones. Under the guidance of TDEM quasi-three-dimensional inversion resistivity data, the low-resistivity karst development area is avoided, and the specific drilling location of well QM2 is determined. No karst cave and underground river were drilled in the later drilling process of well QM2, as well as no instability phenomenon occurred. It indicates that the TDEM detection results are consistent with the actual drilling, and the quasi-three-dimensional TDEM inversion interpretation data based on lateral constraints is reliable and can accurately detect the buried karst in the wellsite.

Ab-initio study of structural, electronic, phonon, X-ray spectroscopy, and the optoelectronic properties of D-block metals (Cr, Mn, Co, and Ni) substitution of barium oxide based-perovskites

Recently, transition metal doped superlattice has shown an anomalous optical band gap of 1.6 eV, about 1 eV lower than either parent element (Barium) majorly, making it appropriate for several applications including magnetism and superconducting materials. In the current study, the structural, electronic, phonon, thermodynamic, and the magnetic ordering of BaXO3 (X = Cr, Mn, Co, and Ni) has been examined using density functional theory (DFT). From the results, the investigated materials show a ferromagnetic behavior with the band gap of range 0.95–1.04 eV, and average absolute magnetization are 2.64, 3.67, 3.19, and 0.01 Bohr magneton/cell for BaCrO3, BaMnO3, BaCoO3, and BaNiO3, respectively. Furthermore, it is conceivable that the Compton profiles of BaXO3(X= Cr, Mn, Co, and Ni) are magnetic due to the substantial exchange-correlation dependence of their Compton profiles, which is shown from the phonon and X-ray distributions, thermodynamic calculation, and mechanically portrayed features of BaXO3. It was further discovered that doping could increase each TM (Cr, Mn, Co, and Ni) atom's magnetic moment. This study demonstrates a novel method for utilizing this revolutionary kind of cubic ferrites for spintronic applications in solid-state electronics.

An Adversarial Time–Frequency Reconstruction Network for Unsupervised Anomaly Detection

Detecting anomalies in massive volumes of multivariate time series data, particularly in the IoT domain, is critical for maintaining stable systems. Existing anomaly detection models based on reconstruction techniques face challenges in distinguishing normal and abnormal samples from unlabeled data, leading to performance degradation. Moreover, accurately reconstructing abnormal values and pinpointing anomalies remains a limitation. To address these issues, we introduce the Adversarial Time–Frequency Reconstruction Network for Unsupervised Anomaly Detection (ATF-UAD). ATF-UAD consists of a time reconstructor, a frequency reconstructor and a dual-view adversarial learning mechanism. The time reconstructor utilizes a parity sampling mechanism to weaken the dependency between neighboring points. Then attention mechanisms and graph convolutional networks (GCNs) are used to update the feature information for each point, which combines points with close feature relationships and dilutes the influence of abnormal points on normal points. The frequency reconstructor transforms the input sequence into the frequency domain using a Fourier transform and extracts the relationship between frequencies to reconstruct anomalous frequency bands. The dual-view adversarial learning mechanism aims to maximize the normal values in the reconstructed sequences and highlight anomalies and aid in their localization within the data. Through dual-view adversarial learning, ATF-UAD minimizes reconstructed value errors and maximizes the identification of residual outliers. We conducted extensive experiments on nine datasets from different domains, and ATF-UAD showed an average improvement of 6.94% in terms of F1 score compared to the state-of-the-art method.

An anomalous frequency band identification method utilising available healthy historical data for gearbox fault detection

Informative frequency band identification methods are used to automatically design bandpass filters to enhance fault signatures in vibration measurements. Blind and targeted features can be used to guide the frequency band selection process. Blind features’ performance is impeded when there are dominant non-stationary extraneous components, whereas targeted features’ performance is impeded when the characteristic frequency of the machine component is unknown, erroneously estimated or the damaged component is not targeted. An anomalous frequency band identification method is proposed that utilises the available historical data to detect weak damage components that deviate from the baseline or reference condition. This makes it possible to ignore dominant extraneous components that are also present in the historical dataset. The proposed method is analysed and compared against conventional and feature ratio methods on numerical and experimental datasets. The results demonstrate that the proposed method has much potential for identifying informative frequency bands for fault detection.

Prospectives for AlN electronics and optoelectronics and the important role of alternative synthesis

Future applications for emerging AlN semiconductor electronics and optoelectronics are facilitated by emerging doping technologies enabled by low temperature, non-equilibrium epitaxy. Defect and impurity compensation can be reduced by controlling the surface chemistry with reducing compensating vacancy concentrations being a key driver for lower temperature growth. Contrary to common understanding, low temperature, metal-rich vacuum processes are shown to have higher diffusion lengths than high temperature nitrogen-rich methods. This feature can be utilized to inhibit silicon-DX center formation without compromises in crystal quality. First principles calculations identify the valence split-off band as the dominant hole band contributing to impurity band formation (as opposed to the heavy and light hole bands in other nitrides). This anomalous band structure causes an impurity band to form at dopant concentrations similar to GaN even though AlN has a deeper isolated acceptor energy and results in hole mobilities that are substantially higher than possible in GaN. AlN hole concentrations of ∼4.4 × 1018 cm−3 and 0.045 Ω cm resistivity and electron concentrations of ∼6 × 1018 cm−3 and ∼0.02 Ω cm resistivity are shown and offer substantial promise for future generations of AlN bipolar electronic and optical devices.

Anomalous bluish-green light emitting features of europium doped barium aluminate (BaAl2O4:Eu2+) phosphor

Eu doped barium aluminate is an important material for light emitting devices. Here we report structural, optical absorption and emission features of 1–5 % Eu doped barium aluminate phosphor and explore its ‘anomalous’ emission feature. The structural analysis suggests that the undoped sample has a mixture of BaAl2O4 and BaAl12O19. On the other hand, the samples doped with Eu have a mixture of BaAl2O4, Ba(Al2O4) and BaAl12O19 phases. Among these, the major phase in all the samples was BaAl2O4. The undoped sample shows a high absorption peak at around 209 nm followed by three weak intensity peaks apparent at around 250, 288 and 338 nm. In contrast, all the doped samples show three maxima at around 209, 266 and 340 nm. The position and intensity of these absorption maxima are found to vary with the Eu concentration. The optical bandgap of the undoped sample is estimated to be 5.05 eV and it is found to reduce to 4.68 eV after doping of Eu at 5 %. All the samples produce common PL emission peaks centred at ∼405, 428 and 456 nm due to potential oxygen vacancies. The doped samples show additional peaks at around 485, 518 and 657 nm due to Eu2+ and Eu3+ ions. In particular, the sample doped with 2 % of Eu produces a strong anomalous emission band of Eu2+ ion in the bluish-green region. Our study reveals that the broadband bluish-green emission of Eu2+ ions can be achieved when the barium aluminate crystal is doped by 2 % of Eu. When the host is doped by Eu at >2 % or <2 %, the emission band associated with oxygen vacancies dominates over the Eu2+ emission.

A Case of Acute Intestinal Obstruction in an Infant during the COVID-19 Pandemic

Abstract Anomalous congenital bands are rare causes of intestinal obstruction in children, adults, and neonates. They are rarely reported, and their etiopathogenesis is unknown, without malrotation in children. Their presentation and radiographic features are similar to any acute intestinal obstruction. The author found approximately 50 similar cases in the literature; however, during and after COVID-19 pandemic, this is the first case of anomalous congenital obstructing band without mal rotation to be reported to date. This is a rare case of infantile intestinal obstruction managed during COVID-19 pandemic. Acute intestinal obstruction due to a congenital anomalous band is rare in infants and children, and if not treated promptly, can lead to morbidity and mortality. Various reasons, such as congenital, acquired, and extrinsic or intrinsic pathologies in children and adults, may be the cause for acute intestinal obstruction. Congenital anomalous bands account for 3% of the intestinal obstructions in infants and children. These bands may cause ischemia and gangrene of the bowel without timely intervention.

Group delay compensation based on negative group velocity effect of spoof surface plasmon polaritons

Negative group velocity (NGV) exists only in the anomalous dispersion band with resonance absorption. In this paper, it is verified that spoof surface plasmon polaritons (SSPPs) with spiral-shaped periodic units have the NGV characteristics near cutoff frequency. The negative group delay of this NGV SSPP can be used to achieve the compression of the pulse signal, and also to compensate the positive group delay with high efficiency. Of course, this group delay compensation scheme based on NGV may introduce an absorption loss, which is the characteristic of all passive negative group delay circuits.

Higher-order topological superconductivity in twisted bilayer graphene

Twisted bilayer graphene, by nature of its symmetries (like the approximate particle-hole symmetry) and anomalous band structure, realizes a higher-order topological superconductor when $s$-wave pairing is introduced via proximity. Here, the authors demonstrate this exotic phase numerically and analytically, and illustrate a multitude of consequences: zero modes bound to Abrikosov vortices, the fractional Josephson effect, and much more.

Negative group velocity characteristics of spoof surface plasmon polaritons

Although there have been many discussions on negative group velocity (NGV), disagreements over its counter-intuitive explanations are still on the way. In this paper, it is proposed that the negative group velocity is just a component of the actual wave group, which has to be accompanied by a positive group velocity (PGV) component. A composite wave with the NGV component propagates forward in the form of a tumbling vortex as an attenuated or evanescent wave. Negative group velocity exists only in the anomalous dispersion band with resonance absorption. This wave group model is confirmed by the NGV characteristics of spoof surface plasmon polaritons (SSPPs) of spiral-shaped periodic units. In this case, the PGV and NGV waves are formed by the resonance coupling of periodic cells, and the composite SSPP modes have both resonance absorption attenuation and vortex cancellation attenuation.

Spin-polarized spatially indirect excitons in a topological insulator.

The exciton, a bound state of an electron and a hole, is a fundamental quasiparticle induced by coherent light-matter interactions in semiconductors. When the electrons and holes are in distinct spatial locations, spatially indirect excitons are formed with a much longer lifetime and a higher condensation temperature. One of the ultimate frontiers in this field is to create long-lived excitonic topological quasiparticles by driving exciton states with topological properties, to simultaneously leverage both topological effects and correlation1,2. Here we reveal the existence of a transient excitonic topological surface state (TSS) in a topological insulator, Bi2Te3. By using time-, spin- and angle-resolved photoemission spectroscopy, we directly follow the formation of a long-lived exciton state as revealed by an intensity buildup below the bulk-TSS mixing point and an anomalous band renormalization of the continuously connected TSS in the momentum space. Such a state inherits the spin-polarization of the TSS and is spatially indirect along the z axis, as it couples photoinduced surface electrons and bulk holes in the same momentum range, which ultimately leads to an excitonic state of the TSS. These results establish Bi2Te3 as a possible candidate for the excitonic condensation of TSSs3 and, in general, opens up a new paradigm for exploring the momentum space emergence of other spatially indirect excitons, such as moiré and quantum well excitons4-6, and for the study of non-equilibrium many-body topological physics.

Tuning Anomalous Floquet Topological Bands with Ultracold Atoms.

The Floquet engineering opens the way to create new topological states without counterparts in static systems. Here, we report the experimental realization and characterization of new anomalous topological states with high-precision Floquet engineering for ultracold atoms trapped in a shaking optical Raman lattice. The Floquet band topology is manipulated by tuning the driving-induced band crossings referred to as band inversion surfaces (BISs), whose configurations fully characterize the topology of the underlying states. We uncover various exotic anomalous topological states by measuring the configurations of BISs that correspond to the bulk Floquet topology. In particular, we identify an unprecedented anomalous Floquet valley-Hall state that possesses anomalous helical-like edge modes protected by valleys and a chiral state with high Chern number.

Surface Quantum-Dimensional Photocarrier Recombination in &amp;lt;i&amp;gt;CdTe&amp;lt;/i&amp;gt; Microcrystals

The scope of the study is the spectra of low-temperature (T = 2K) photoluminescence of a p-CdTe/n-CdS film heterostructure comprising a monolayer of CdTe microcrystals, where a single microcrystalline particle is typically one micron in size. Focus is made on the dominant band of “super-hot” emission appearing in the spectral region located in energy above the fundamental absorption edge of a CdTe bulk crystal. A theoretical model has been developed that assumes the existence of a space-charge layer inside a microcrystal, which leads to the formation of a triangular potential well for an electron near the surface. The anomalous emission band arises as a result of the optical transitions of electrons from near-surface levels of spatial quantization to valence band states.

Optical study of oriented double-Se8-ring clusters and luminescent Se2− anions in LTA at extremely high selenium loading density

Recently, LTA-Se(1–8) samples with 1–8 Se atoms per cavity (simplified unit cell, large cavity + sodalite cage) obtained via adsorption at the temperature of ∼450 °C were reported. It was shown that single Se8 or single Se12 ring are formed in the large LTA cavities, Se8/Se12 ring concentration ratio decreasing with an increase in the Se loading density. Contrary, in the present work, using Se vapour adsorption at ∼550 °C, we succeeded in encapsulation of ∼17 Se atoms per cavity (LTA-Se(17)) with a significant increase in the Se8/Se12 concentration ratio manifesting double Se8-ring cluster formation in the most of the LTA large cavities, which is a step towards cluster crystal fabrication. According to our polarization/orientation Raman spectroscopic study of LTA-Se(17) single crystals, the orientations of the Se8 and Se12 appeared to be similar to those in previously investigated LTA-Se(1–8). Importantly, luminescent Se2− anions, oriented along the LTA 4-fold axes and located in the sodalite cages, are detected via Raman polarization/orientation dependencies of LTA-Se(17). Bright Se2− light emission with a maximum at ∼1.56 eV and vibronic structure is observed in the 1.3–1.8 eV spectral range. We show that the anions experience a compression in LTA which is slightly relaxing with a decrease in temperature producing an anomalous Raman band downshift. The compression of Se2− in LTA is weaker/stronger than that in sodalite/cancrinite, luminescence band photon energy depending on its strength. High concentration of regularly arranged Se2− in LTA suggests considering LTA-Se(17) as an important novel light-emitting material.

Supernumerary Extraocular Muscle: A Rare Cause of Atypical Restrictive Strabismus.

Background and objectives: Supernumerary extraocular muscle (SEOM) is extremely rare. The purpose of this paper was to review the clinical characteristics and surgical outcomes of SEOM patients with atypical restrictive strabismus. Materials and Methods: A retrospective review was conducted on the data from 12 SEOM cases. Pre- and post-operative measurements consisted of visual acuity, cycloplegic refraction, ocular alignment, ocular motility, binocular vision, and imaging. Management strategies included either conservative or surgical treatments. Results: Of the 12 cases reviewed (seven females, five males), the mean ± SD age was 14.3 ± 10.6 years (range: 4-38 years). The right eye was affected in six cases, the left in five, and both eyes in one case. The major clinical manifestations included restrictive ocular motility (12 cases), with seven cases in no less than three directions; varying degrees of horizontal or vertical strabismus; ipsilateral amblyopia (10 cases); and unequal palpebral aperture (10 cases). Imaging results revealed muscular bands originating from the annulus of Zinn and insertion into the globe or other recti, as well as anomalous muscular bands connecting two or more recti, sometimes with optic nerve involvement. Three patients received conservative treatment, while rectus recession with or without resection (seven patients) or rectus disinsertion plus globe fixation (two patients) were performed in those receiving surgical treatments. A surgical success was achieved in four cases. Conclusions: For restrictive strabismus, imaging plays an important role in the diagnosis of SEOM. When the SEOM is difficult to resect, a personalized surgical strategy may be required to achieve a good ocular alignment.