Ground State Research Articles

Hidden in life, forgotten in death

In this comment piece, Peter Nolan explores the history of burials for patients admitted to mental health asylums and the state of these burial grounds in the present-day UK.

Material gain and two-state lasing in quantum well-dot lasers

We report on modal and material gains as well as two-state lasing in lasers based on quantum well-dots (QWDs)–quantum heterostructures of mixed dimensionality (0D/2D). A high ground-state (GS) modal gain of 100 cm−1 is revealed in the device based on a single QWD layer. The upper limit of the GS material gain is estimated as 2.2 × 104 cm−1. In narrow-ridge 200 μm long lasers, pure GS lasing occurs up to a pumping current density that exceeds the threshold value by 17.5 times. A decrease in the optical confinement factor results in lasing via an excited state (ES) at a high pumping current. In the current range corresponding to the GS lasing, the devices operate in the transverse fundamental optical mode, whereas above the ES lasing threshold, they operate in the second order mode. In narrow-ridge lasers, the ES lasing is observed in longer cavities and at lower threshold current densities than in broad-area lasers.

Grinding state recognition of arc-shaped CVD diamond tools based on multi-scale acoustic emission features

Grinding state recognition of arc-shaped CVD diamond tools based on multi-scale acoustic emission features

Structure-Property Relationship in the Kagomé Net Intermetallic Co3Ge2Sb

Layered intermetallic compounds with kagomé nets are of recent interest due to the topologically protected flat bands shown in many cases. Examples of interesting electronic grounds states range from the topological hall effect (THE) (YMn6Sn6) to superconductivity (MgCo6Ge6). This ongoing work investigates the structure-property relationship of one mostly overlooked example, Co3Ge2Sb. It can be seen as a distorted form of previously studied compounds such as CoSn and MgCo6Ge6. Using Zintl-based electron counting rules, we present a different perspective on the origin of dimer formation in MgCo6Ge6 and related '166' (aka 'stuffed CoSn') compounds, which we further validate with electronic structure calculations. Additionally, symmetry mode analysis enables contrasts to be drawn between the structural distortion in Co3Ge2Sb-type structure and the charge density wave (CDW) ordering observed in FeSn and the AV3Sb5 (A = K, Rb, Cs) family of superconductors. These findings provide new tools for understanding the structure-property relationship in the broader class of layered kagomé net materials.

Giant low-field magnetocaloric effect in unstable antiferromagnetic Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds

Giant low-field magnetocaloric effect in unstable antiferromagnetic Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds

A visualization method for cross-scale online monitoring of grinding state based on data-mechanism hybrid-driven digital twin system

A visualization method for cross-scale online monitoring of grinding state based on data-mechanism hybrid-driven digital twin system

Study on the Relationship Between Vibration Signals in CFRP Grinding and Grinding Mechanism

Abstract In the process of grinding carbon fiber reinforced polymer (CFRP), the changing state of acceleration vibration signal is closely related to the grinding surface quality. Therefore, the time domain and frequency domain signal changes in acceleration can be used to monitor and control the grinding process to improve machining quality and efficiency. In this paper, changes in acceleration frequency domain signals under different grinding angles are studied, and the relationship between the vibration forms of acceleration frequency domain signals at the beginning, middle and end of grinding as well as the surface morphology and quality of the corresponding grinding position is studied. Combined with the micro-morphology of the grinding area, it can be seen that, a high frequency and low amplitude vibration can improve the grinding surface quality, but a high amplitude will have a negative impact on the grinding quality. The acceleration vibration during grinding is more stable and the corresponding surface quality is better. With an increase in grinding angle, the maximum amplitude of acceleration first increases and then decreases. The length of the surface fiber also initially decreases and then increases. Lastly, the resin residue first increases and then decreases. The purpose of this study is to provide a theoretical basis for the subsequent grinding state adjustment.

Study on wear state of ultrasonic-assisted grinding of glass-ceramics with diamond tools based on DBO-BiLSTM

With the development of precision manufacturing technology, diamond tools play a vital role in industrial machining because of their high hardness and excellent wear resistance. However, tool wear can seriously affect machining accuracy and efficiency. In order to ensure the efficient and high-quality machining, it is of paramount importance to monitor the state of the tools used with the utmost accuracy. First, the fixed area of the diamond tool after machining was observed. The ratio of the number of abrasive particles falling off and the presence of scratches in the matrix were used as the evaluation indexes of the wear state of the diamond tool. The vibration signal was used as a monitoring signal to identify the wear state of the diamond tools. To obtain a feature set sensitive to the tool wear state, the vibration signal was analyzed in the time domain, frequency domain, and wavelet packet. The dimensionality of the sensitive feature set is reduced through the application of principal component analysis (PCA). The tool wear state was identified using the dung beetle optimizer bidirectional long short-term memory (DBO-BiLSTM) model and the bidirectional long short-term memory (BiLSTM) model. The results demonstrate that the DBO-BiLSTM has a higher accuracy in wear state identification, showing an improvement of 10.05% over the BiLSTM. Moreover, optimizing feature dimension reduction can enhance the model’s identification accuracy.

What is the true ground state of intermetallic compound Fe3Al?

What is the true ground state of intermetallic compound Fe3Al?

The Reality of The State's Responsibility for Victims of Natural Disasters in The Perspective of Human Rights

This study critically examines the state's role in fulfilling its responsibilities towards victims of natural disasters from a human rights perspective. It aims to analyze the nature of these responsibilities, their conceptual framework, and the factors influencing their effective implementation. Using a philosophical approach alongside qualitative research methods like interviews and direct observations, the study seeks to deepen understanding of how state actions intersect with humanitarian principles. Key findings emphasize the importance of grounding state responsibilities in humanitarian values to uphold human rights and preserve the dignity of affected individuals. This perspective is particularly relevant in Indonesia, where Pancasila principles underscore the state's role in disaster response and recovery. Despite these principles, the study identifies persistent challenges such as inadequate disaster mitigation policies, insufficient community protection measures, and complexities in inter-governmental coordination. To enhance the implementation of state responsibilities in disaster management, several recommendations are proposed. Firstly, integrating humanitarian considerations into criteria for determining national disaster status is essential to prioritize human rights in decision-making. Secondly, regional governments should allocate resources in their budget planning for both proactive disaster prevention and effective post-disaster response tailored to local vulnerabilities. Additionally, the study advocates for improved disaster mitigation policies, including comprehensive public education on disaster impacts, strict building regulations, and robust disaster risk zoning frameworks. Addressing these recommendations can align state actions with humanitarian principles, thereby improving the protection and well-being of communities affected by natural disasters.

Ground state of the Gross–Pitaevskii equation with a harmonic potential in the energy-critical case

Ground state of the energy-critical Gross–Pitaevskii equation with a harmonic potential can be constructed variationally. It exists in a finite interval of the eigenvalue parameter. The supremum norm of the ground state vanishes at one end of this interval and diverges to infinity at the other end. We explore the shooting method in the limit of large norm to prove that the ground state is pointwise close to the Aubin–Talenti solution of the energy-critical wave equation in near field and to the confluent hypergeometric function in far field. The shooting method gives the precise dependence of the eigenvalue parameter versus the supremum norm.

Equilibria and dynamics of two coupled chains of interacting dipoles.

We explore the energy transfer dynamics in an array of two chains of identical rigid interacting dipoles. Varying the distance b between the two chains of the array, a crossover between two different ground-state (GS) equilibrium configurations is observed. Linearizing around the GS configurations, we verify that interactions up to third nearest neighbors should be accounted to accurately describe the resulting dynamics. Starting with one of the GS, we excite the system by supplying it with an excess energy ΔK located initially on one of the dipoles. We study the time evolution of the array for different values of the system parameters b and ΔK. Our focus is hereby on two features of the energy propagation: the redistribution of the excess energy ΔK among the two chains and the energy localization along each chain. For typical parameter values, the array of dipoles reaches both the equipartition between the chains and the thermal equilibrium from the early stages of the time evolution. Nevertheless, there is a region in parameter space (b,ΔK) where even up to the long computation time of this study, the array does neither reach energy equipartition nor thermalization between chains. This fact is due to the existence of persistent chaotic breathers.

Comparative study of experimental and DFT calculations for 3-cinnamoyl 4-hydroxycoumarin derivatives.

Computational research plays an important role in predicting the chemical and physical properties of biologically active compounds important in future structural modifications to improve or modify biological activity. This research focuses on quantum chemical and spectroscopic investigations properties of synthesized 4-hydroxycoumarin derivatives. Quantum chemical calculations were obtained using B3LYP, HF, and M06-2x level methods with the 6-31++G (d,p) basis set. Afterward, IR, 1H, 13C, UV-Visible experimentally parameters were compared with the results obtained using the B3LYP/6-31+G*(d) basis set of the molecules to be able to characterize the structures. Based on the quantum chemical calculations compound with acetamido group on the phenyl ring is the most reactive, and compound with nitro substituent is the least reactive and the the strongest electrophile among tested compounds. With the exception of compounds with dimethylamino group, all other compounds have a pronounced tautomer between OH and C = O group. The calculated and experimental values are in agreement with each other. The molecular structure in the ground state of six 3-cinnamoyl 4-hydroxycoumarin derivatives was optimized using density functional theory. The observed and computed values were compared and it can be concluded that the theoretical results were in good linear agreement with the experimental data.

Numerical investigation on nonlinear dynamics of two-state quantum dot laser subject to optical injection

Based on the cascade relaxation model of the quantum dot (QD) lasers, the nonlinear dynamics of a two-state QD laser subject to optical injection is numerically studied. The simulation results show that, for a two-state QD laser operating at the ground-state (GS) and excited-state (ES) emission simultaneously, through adjusting the injection parameters, the two emission states can display the stable (S), injection locking (IL), suppression (SP), period-one (P1), period-two (P2), multi-period (MP), and chaotic pulse (CP) states when the frequency of the injection light is close to the GS lasing frequency. Further mapping of these dynamic states in the parameter space of frequency detuning and injection strength, it is found that the complex dynamic behaviors are mainly distributed in the negative frequency detuning region. In addition, the complexity of the chaotic signal is qualified by the permutation entropy (PE) calculating, and the high complexity signal with PE value over 0.95 is obtained. Moreover, within a certain frequency detuning range, the ES emission can be effectively suppressed by increasing the injection strength.

Polycationic Open‐Shell Cyclophanes: Synthesis of Electron‐Rich Chiral Macrocycles, and Redox‐Dependent Electronic States

Abstractπ‐Conjugated chiral nanorings with intriguing electronic structures and chiroptical properties have attracted considerable interests in synthetic chemistry and materials science. We present the design principles to access new chiral macrocycles (1 and 2) that are essentially built on the key components of main‐group electron‐donating carbazolyl moieties or the π‐expanded aza[7]helicenes. Both macrocycles show the unique molecular conformations with a (quasi) figure‐of‐eight topology as a result of the conjugation patterns of 2,2’,7,7’‐spirobifluorenyl in 1 and triarylamine‐coupled aza[7]helicene‐based building blocks in 2. This electronic nature of redox‐active, carbazole‐rich backbones enabled these macrocycles to be readily oxidized chemically and electrochemically, leading to the sequential production of a series of positively charged polycationic open‐shell cyclophanes. Their redox‐dependent electronic states of the resulting multispin polyradicals have been characterized by VT‐ESR, UV/Vis‐NIR absorption and spectroelectrochemical measurements. The singlet (ΔES‐T=−1.29 kcal mol−1) and a nearly degenerate singlet‐triplet ground state (ΔES−T(calcd)=−0.15 kcal mol−1 and ΔES−T(exp)=0.01 kcal mol−1) were proved for diradical dications 12+2⋅ and 22+2⋅, respectively. Our work provides an experimental proof for the construction of electron‐donating new chiral nanorings, and more importantly for highly charged polyradicals with potential applications in chirospintronics and organic conductors.

Polycationic Open-Shell Cyclophanes: Synthesis of Electron-Rich Chiral Macrocycles, and Redox-Dependent Electronic States.

π-Conjugated chiral nanorings with intriguing electronic structures and chiroptical properties have attracted considerable interests in synthetic chemistry and materials science. We present the design principles to access new chiral macrocycles (1 and 2) that are essentially built on the key components of main-group electron-donating carbazolyl moieties or the π-expanded aza[7]helicenes. Both macrocycles show the unique molecular conformations with a (quasi) figure-of-eight topology as a result of the conjugation patterns of 2,2',7,7'-spirobifluorenyl in 1 and triarylamine-coupled aza[7]helicene-based building blocks in 2. This electronic nature of redox-active, carbazole-rich backbones enabled these macrocycles to be readily oxidized chemically and electrochemically, leading to the sequential production of a series of positively charged polycationic open-shell cyclophanes. Their redox-dependent electronic states of the resulting multispin polyradicals have been characterized by VT-ESR, UV/Vis-NIR absorption and spectroelectrochemical measurements. The singlet (ΔES-T=-1.29 kcal mol-1) and a nearly degenerate singlet-triplet ground state (ΔES-T(calcd)=-0.15 kcal mol-1 and ΔES-T(exp)=0.01 kcal mol-1) were proved for diradical dications 12+2⋅ and 22+2⋅, respectively. Our work provides an experimental proof for the construction of electron-donating new chiral nanorings, and more importantly for highly charged polyradicals with potential applications in chirospintronics and organic conductors.

Scale Invariance in the Lowest Landau Level

We show that the discrete set of pair amplitudes $A_m$ introduced by Haldane are an angular-momentum resolved generalization of the Tan two-body contact, which parametrizes universal short-range correlations in atomic quantum gases. The pair amplitudes provide a complete description of translation-invariant and rotation-invariant states in the lowest Landau level (LLL), both compressible and incompressible. To leading nontrivial order beyond the non-interacting high-temperature limit, they are determined analytically in terms of the Haldane pseudopotential parameters $V_m$, which provides a qualitative description of the crossover towards incompressible ground states for different filling factors. Moreover, we show that for contact interactions $\sim g_2 \delta^{(2)}({\bf x})$, which are scale invariant at the classical level, the non-commutativity of the guiding center coordinates gives rise to a quantum anomaly in the commutator $i [\hat{H}_{\rm LLL}, \hat{D}_R] = (2 + \ell \partial_\ell) \hat{H}_{\rm LLL}$ with the dilatation operator $\hat{D}_R$ in the LLL, which replaces the trace anomaly in the absence of a magnetic field. The interaction-induced breaking of scale invariance gives rise to a finite frequency shift of the breathing mode in a harmonic trap, which describes transitions between different Landau levels, the strength of which is estimated in terms of the relevant dimensionless coupling constant $\tilde{g}_2$.

Order-by-disorder and long-range interactions in the antiferromagnetic transverse-field Ising model on the triangular lattice—A perturbative point of view

We study the low-field ground-state (GS) properties of the antiferromagnetic transverse-field Ising model with long-range interactions (afLRTFIM) on the triangular lattice. We use the method of perturbative continuous unitary transformations (pCUT) to derive an effective model for the degenerate GS space of the antiferromagnetic nearest-neighbour (NN) Ising model on a finite system, by treating the transverse-field (TF) and the long-range interactions (LRI) as a perturbation. We determine a level-crossing between the gapped plain stripe phase at small TF and the gapped clock-ordered phase at intermediate TF at hc≅0.129 for α=6, N=36 spins in order three perturbation theory on the finite system. We discuss the qualitative layout of the quantum phase diagram of the afLRTFIM on the triangular lattice.

Near-IR-Absorbing Bis-Donor Functionalized Aza-BODIPY Derivatives: Synthesis and Photophysical Study by Using Transient Optical Spectroscopy.

A series of near-IR absorbing 2,6-diarylated BF2-chelated aza-boron-dipyrromethenes (aza-BDPs) derivatives bearing different electron donors (benzene, naphthalene, phenanthrene, phenothiazine and carbazole) were designed and synthesized. The effect of different electron donor substitutions on the photophysical properties was studied by steady-state UV-vis absorption and fluorescence spectra, electrochemical, time-resolved nanosecond transient absorption (ns-TA) spectroscopy and theoretical computations. The UV-vis absorption spectra of AzaBDP-PTZ and AzaBDP-CAR (λabs=710 nm in toluene) showed a bathochromic absorption profile compared with the reference AzaBDP-Ph (λabs=685 nm in toluene), indicating the non-negligible electronic interaction at the ground state between donor and acceptor moieties. Moreover, the fluorescence is almost completely quenched for AzaBDP-PTZ/AzaBDP-CAR (fluorescence quantum yield, ΦF=0.2-0.7 % in toluene) as compared with the AzaBDP-Ph (ΦF=27 % in toluene). However, the apparent intersystem crossing ability of these compounds is poor, based on the singlet oxygen quantum yield (ΦΔ=0.3-1.5 %). The ns-TA spectral study showed typical Bodipy localized triplet state transient features, short-lived excited triplet state for AzaBDP-Ph (τT=53.2 μs) versus significantly long-lived triplet state for AzaBDP-CAR (τT=114 μs) was observed under deaerated experimental conditions. These triplet state lifetimes are much longer than that obtained with diiodoAzaBDP (intramolecular heavy atom effect, τT=1.5~7.2 μs). These information are useful for molecular structure design of triplet photosensitizers, for which longer triplet state lifetimes are usually desired. Theoretical computations displayed that the triplet state is mainly localized on the AzaBDP core, moreover, it was found that the HOMO/LUMO energy gap decreased after introducing donor moieties to the skeleton as compared with the reference.

Effect of non-uniform carrier injection on two-state lasing in quantum dot microdisks with split electrical contact

In this papaer, the emission characteristics of InAs/InGaAs quantum dot (QD) microdisk lasers, of different cavity diameters, with a top split electrical contact formed using the focused ion beam technique are investigated. The dependences of the threshold currents of two-state lasing (i.e. currents corresponding to the start of the ground- and excited-state lasing) for microdisks of 24 and 28 μm diameters on the electrical contact area are presented. The contact area was found to influence the threshold currents of two-state lasing in microdisks. It is shown that a decrease in the area of the injected electrical contact leads to a decrease in the current corresponding to the start of the excited-state lasing, while the ground-state (GS) lasing threshold remains virtually unchanged. The temperature evolution of the threshold currents for two-state lasing was also studied in microdisks with different electrical contact areas. We demonstrate that the use of contacts of different areas is a method of controlling the threshold currents of two-state lasing and can be used in engineering of QD lasers intended, for example, for multi-level signal transmission with wavelength multiplexing by switching from the GS to excited-state lasing.