Central Charge Research Articles

Multifunctional surface modification of carbon-based all-inorganic CsPbI2Br solar cells by 3-(trifluoromethyl) phenyltrimethyl ammonium iodide

The preparation process of carbon-electrode perovskite solar cells (C-PSCs) without hole transport layers (HTLs) is simple, cost-effective, and the as-prepared C-PSCs exhibit excellent thermal stability. However, there are numerous defects at the interfaces of C-PSCs and grain boundaries. Due to the presence of these defect states, non-radiative recombination of charge carriers occurs, ultimately resulting in significant VOC (voltage open circuit) loss and an energy level mismatch between device structures, which seriously affect the photoelectric conversion efficiency (PCE) and stability of C-PSCs. Therefore, this work uses 3-(trifluoromethyl)-phenyltrimethyl-ammonium iodide (TFPTAI) as a surface modifier to modify the surface of CsPbI2Br. Due to the strong electronegativity of fluorine atoms (F), acting as electron-withdrawing groups, they promote the separation of positive and negative charge centers in the molecule. This, in turn, can effectively induce strong binding of ammonium cations (NH+) with negatively charged defects, consequently suppressing the non-radiative recombination of charge carriers. In addition, thanks to the ordered arrangement of F atoms, a hydrophobic protective umbrella is constructed on the perovskite surface layer, effectively improving the stability of the device. The highest PCE of the as-prepared device is 14.02%, surpassing the optimal PCE of the original device at 12.46%. Simultaneously, the surface-modified device exhibits excellent environmental stability.

Laser Synthesis of Catalytically Active Materials for Organic Synthesis and Sensor Technology

Introduction: The catalytic activity of metallic nanomaterials depends on their surface morphology. A widely known method is the laser synthesis of metal nanostructures by depositing on dielectric surfaces from aqueous solutions containing metal complexes. The article analyzes the factors that favor the production of conductive, catalytic, and sensory-active deposits by laser method. It is shown that the two main factors is the presence of a large number of charged defects on heterophase surfaces and the structure of metal-containing complexes in solution. This is typical for mono- and bimetallic alloys, the components of which interact with the laser beams according to the autocatalytic type. Using the example of laser deposition from solutions of Co, Ni, Fe, Zn, and Ag salts with homo- and heterophase dielectrics, the sensory and catalytic properties of the deposits are compared by impedance spectroscopy and voltammetry. It has been shown that heterophase precipitation significantly enhances the catalysis response. Background: It is known that the highest catalytic activity exhibits nanostructured and highly porous materials with a large specific surface area and materials containing surface heterogeneity in the form of charged acid-base centers. Such materials are necessary for the creation of new catalysts for organic synthesis and for the creation of new sensor materials for enzyme-free microbiosensors. Active development of new methods for the synthesis of such materials is underway. But not all of them give the expected result. Methods: Laser synthesis methods have the best prospects, including the method of laser-induced metal deposition. This is the laser synthesis of metal nanostructures by depositing dielectric surfaces from aqueous solutions containing metal complexes. Results: Аrticle analyzes the factors that favor the production of conductive, catalytic, and sensory-active deposits by laser method. It is shown that the two main factors are the presence of a large number of charged defects on heterophase surfaces and the structure of a metal-contained complex in solution. This is typical for mono- and bimetallic alloys, the components of which interact with the laser beam according to the autocatalytic type. Using the example of laser deposition from solutions of Co, Ni, Fe, Zn, and Ag salts with homo- and heterophase dielectrics, the sensory and catalytic properties of the deposits are compared by impedance spectroscopy and voltammetry. Conclusion: It has been shown that heterophase precipitation significantly enhances the catalysis response. It is shown that the laser deposition reaction has an autocatalytic mechanism in a dynamic mode. The results of autocatalysis can be used in a stationary mode to create a microbiosensor for glucose, as well as to create a technology for laser refining rare metals and hydrogen energy in a dynamic mode.

Black holes thermodynamics with CFT re-scaling

In this paper, we study the thermodynamic behavior of charged AdS black holes in a conformal holographic extended thermodynamic. Our setup is constructed using a new dictionary that relates AdS black hole quantities to the corresponding dual conformal fields theory (CFT) one, with the conformal factor being treated as a variable thermodynamic. In this thermodynamic study, we investigate the critical phenomena of charged AdS black holes and their relationship to the central charge value, C. Additionally, we examine the phase transitions and black holes stability using the free energy and the heat capacity, respectively. Furthermore, by examining the chemical potential, we establish a criteria that differentiate between quantum and classical black hole’s behaviors. Our setup highlights one of the key findings, namely traditional black hole thermodynamics acts as a boundary between quantum and classical regimes.

Generalized symmetries and anomalies of 3d $\mathcal{N}=4$ SCFTs

We study generalized global symmetries and their ’t Hooft anomalies in 3d \mathcal{N}=4𝒩=4 superconformal field theories (SCFTs). Following some general considerations, we focus on good quiver gauge theories, comprised of balanced unitary nodes and unbalanced unitary and special unitary nodes. While the global form of the Higgs branch symmetry group may be determined from the UV Lagrangian, the global form of Coulomb branch symmetry groups and associated mixed ’t Hooft anomalies are more subtle due to potential symmetry enhancement in the IR. We describe how Coulomb branch symmetry groups and their mixed ’t Hooft anomalies can be deduced from the UV Lagrangian by studying center charges of various types of monopole operators, providing a concrete and unambiguous way to implement ’t Hooft anomaly matching. The final expression for the symmetry group and ’t Hooft anomalies has a concise form that can be easily read off from the quiver data, specifically from the positions of the unbalanced and flavor nodes with respect to the positions of the balanced nodes. We provide consistency checks by applying our method to compute symmetry groups of 3d \mathcal{N}=4𝒩=4 theories corresponding to magnetic quivers of 4d Class S theories and 5d SCFTs. We are able to match these results against the flavor symmetry groups of the 4d and 5d theories computed using independent methods. Another strong consistency check is provided by comparing symmetry groups and anomalies of two theories related by 3d mirror symmetry.

Correlation functions of huge operators in AdS3/CFT2: domes, doors and book pages

We describe solutions of asymptotically AdS3 Einstein gravity that are sourced by the insertion of operators in the boundary CFT2, whose dimension scales with the central charge of the theory. Previously, we found that the geometry corresponding to a black hole two-point function is simply related to an infinite covering of the Euclidean BTZ black hole [1]. However, here we find that the geometry sourced by the presence of a third black hole operator turns out to be a Euclidean wormhole with two asymptotic boundaries. We construct this new geometry as a quotient of empty AdS3 realized by domes and doors. The doors give access to the infinite covers that are needed to describe the insertion of the operators, while the domes describe the fundamental domains of the quotient on each cover. In particular, despite the standard fact that the Fefferman-Graham expansion is single-sided, the extended bulk geometry contains a wormhole that connects two asymptotic boundaries. We observe that the two-sided wormhole can be made single-sided by cutting off the wormhole and gluing on a “Lorentzian cap”. In this way, the geometry gives the holographic description of a three-point function, up to phases. By rewriting the metric in terms of a Liouville field, we compute the on-shell action and find that the result matches with the Heavy-Heavy-Heavy three-point function predicted by the modular bootstrap. Finally, we describe the geometric transition between doors and defects, that is, when one or more dual operators describe a conical defect insertion, rather than a black hole insertion.

Direct space–time manipulation mechanism for spatio-temporal coupling of ultrafast light field

Traditionally, manipulation of spatiotemporal coupling (STC) of the ultrafast light fields can be actualized in the space-spectrum domain with some 4-f pulse shapers, which suffers usually from some limitations, such as spectral/pixel resolution and information crosstalk associated with the 4-f pulse shapers. This work introduces a novel mechanism for direct space-time manipulation of ultrafast light fields to overcome the limitations. This mechanism combines a space-dependent time delay with some spatial geometrical transformations, which has been experimentally proved by generating a high-quality STC light field, called light spring (LS). The LS, owing a broad topological charge bandwidth of 11.5 and a tunable central topological charge from 2 to −11, can propagate with a stable spatiotemporal intensity structure from near to far fields. This achievement implies the mechanism provides an efficient way to generate complex STC light fields, such as LS with potential applications in information encryption, optical communication, and laser-plasma acceleration.

Wannier charge center, spin resolved bulk polarization, and corner modes in a strained quantum spin Hall insulator

Wannier charge center, spin resolved bulk polarization, and corner modes in a strained quantum spin Hall insulator

Describing nurses' communication about evidence-based practice change: A social network analysis of hospital nurses.

Nurses play a critical role in providing evidence-based, high-quality care to optimize patient outcomes. Models from implementation science suggest social networks may influence the adoption of evidence-based practices (EBPs). However, few studies have examined this relationship among hospital nurses. Social network analysis (SNA) mathematically evaluates patterns of communication, a critical step in implementation. Exploring hospital nurses' communication networks may provide insight into influences on the adoption of EBPs. This study aimed to describe complete communication networks of hospital nurses for practice changes on inpatient units, including upper level nursing administrators. This descriptive, exploratory, cross-sectional study used SNA on two inpatient units from one hospital. A sociometric survey was completed by nurses (unit to executive level) regarding communication frequency about practice changes. Network-level density, diameter, average path length, centralization, and arc reciprocity were measured. Attribute data were used to explore subnetworks. Surveys from 148 nurses on two inpatient adult intensive care units (response rates 90% and 98%) revealed high communication frequency. Network measures were similar across the two units and among subnetworks. Analysis identified central (charge nurses and nurse leaders) and peripheral members of the network (new-to-practice nurses). Subnetworks aligned with the weekend and shift worked. Established communication channels, including subnetworks and opinion leaders, should be used to maximize and optimize implementation strategies and facilitate the uptake of EBPs. Future work should employ SNA to measure the impact of communication networks on promoting the uptake of EBP and to improve patient outcomes.

Strongly coupled spins of silicon-vacancy centers inside a nanodiamond with sub-megahertz linewidth

Abstract The search for long-lived quantum memories, which can be efficiently interfaced with flying qubits, is longstanding. One possible solution is to use the electron spin of a color center in diamond to mediate interaction between a long-lived nuclear spin and a photon. Realizing this in a nanodiamond furthermore facilitates the integration into photonic devices and enables the realization of hybrid quantum systems with access to quantum memories. Here, we investigated the spin environment of negatively charged silicon-vacancy centers in a nanodiamond and demonstrate strong coupling of its electron spin, while the electron spin’s decoherence rate remained below 1 MHz. We furthermore demonstrate multi-spin coupling with the potential to establish registers of quantum memories in nanodiamonds.

Quantum criticality in chains of planar rotors with dipolar interactions.

In this work, we perform a density matrix renormalization group study of chains of planar rotors interacting via dipolar interactions. By exploring the ground state from weakly to strongly interacting rotors, we find the occurrence of a quantum phase transition between a disordered and a dipole-ordered quantum state. We show that the nature of the ordered state changes from ferroelectric to antiferroelectric when the relative orientation of the rotor planes varies and that this change requires no modification of the overall symmetry. The observed quantum phase transitions are characterized by critical exponents and central charges, which reveal different universality classes ranging from that of the (1 + 1)D Ising model to the 2D classical XY model.

TT¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ T\\overline{T} $$\\end{document}-deformed entanglement entropy for IQFT

We calculate the TT¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ T\\overline{T} $$\\end{document}-deformed entanglement entropy for integrable quantum field theories (IQFTs) using the form factor bootstrap approach. We solve the form factor bootstrap axioms for the branch-point twist fields and obtain the deformed form factors. Using these form factors, we compute the deformed von Neuman entropy up to two particle contributions. The solution of the form factor axioms is not unique. We find that for the simplest solution of the bootstrap axioms, the UV limit of the entanglement entropy takes the same form as the undeformed one, but the effective central charge is deformed. For solutions with additional CDD-like factors, we can have different behaviors. The IR corrections, which only depends on the particle spectrum is untouched.

The promotion mechanism of Mn on the catalytic degradation of benzene by H2O2 on Cu surface: The simultaneous enhancement of OH generation and benzene oxidation by ·OH

It is a promising technology to degrade benzene by using the strong oxidizing ·OH produced by H2O2 decomposition. However, in practical engineering, the low yield and utilization rate of ·OH affect the degradation effect, and the development of new catalysts is the key to solve this problem. The effects of Mn-doped on the decomposition of H2O2 on the surface of Cu (Mn-Cu) to obtain ·OH were studied by combining density functional theory, including the adsorption and decomposition characteristics of H2O2 and the ineffective consumption reaction of ·OH on the surface. At the same time, the specific reaction process between benzene and · OH on the surface was studied, and the effectiveness improvement of various reactions on the surface of Mn-Cu was analyzed in detail. It is found that the charge transfer between Mn and Cu forms positive and negative charge centers on the surface, the O-O bond break of H2O2 molecules that promote adsorption on the surface occurs homolysis, and has a significant inhibitory effect on the ineffective consumption reaction between ·OH and H2O2 molecules and ·HO2, thus improving the yield and utilization of ·OH. At the same time, the reaction energy barrier between ·OH and benzene was significantly reduced, the energy barrier of the first stage of degradation was reduced from 206.86 kJ/mol to 27.02 kJ/mol, and the degradation efficiency of benzene was greatly improved. And the effect improvement was verified through degradation experiments. The degradation rate of Mn-Cu surface is higher than that of Cu surface at all stages, and the final degradation rate can reach about 89%. By clarifying the above reaction mechanism, it provides theoretical support for the development of new catalysts.

Perturbing isoradial triangulations

We consider an infinite planar Delaunay graph \mathbf{G}_{\epsilon} which is obtained by locally deforming the coordinate embedding of a general isoradial graph \mathbf{G}_{\mathrm{cr}} , with respect to a real deformation parameter \epsilon . Using Kenyon’s exact and asymptotic results for the critical Green’s function on an isoradial graph, we calculate the leading asymptotics of the first- and second-order terms in the perturbative expansion of the log-determinant of the Laplace–Beltrami operator \Delta(\epsilon) , the David–Eynard Kähler operator \mathcal{D}(\epsilon) , and the conformal Laplacian {\underline{\boldsymbol{\Delta}}}(\epsilon) on the deformed Delaunay graph \mathbf{G}_{\epsilon} . We show that the scaling limits of the second-order bi-local term for both the Laplace–Beltrami and David–Eynard Kähler operators exist and coincide, with a shared value independent of the choice of the initial isoradial graph \mathbf{G}_{\mathrm{cr}} . Our results allow us to define a discrete analog of the stress-energy tensor for each of the three operators. Furthermore, we can identify a central charge ( c=-2 ) in the case of both the Laplace–Beltrami and David–Eynard Kähler operators. While the scaling limit is consistent with the stress-energy tensor and the value of the central charge for the Gaussian free field (GFF), the discrete central charge value of c=-2 for the David–Eynard Kähler operator is, however, at odds with the value of c=-26 expected by Polyakov’s theory of 2D quantum gravity; moreover, there are problems with convergence of the scaling limit of the discrete stress-energy tensor for the David–Eynard Kähler operator. The second-order bi-local term for the conformal Laplacian involves anomalous terms corresponding to the creation of discrete curvature dipoles in the deformed Delaunay graph \mathbf{G}_{\epsilon} ; we examine the difficulties in defining a convergent scaling limit in this case. Connections with some discrete statistical models at criticality are explored.

Efficient microwave spin control of negatively charged group-IV color centers in diamond

In this paper, we provide a comprehensive overview of the microwave-induced manipulation of electronic spin states in negatively charged group-IV color centers in diamond with a particular emphasis on the influence of strain. Central to our investigation is the consideration of the full vectorial attributes of the magnetic fields involved, which are a dc field for lifting the degeneracy of the spin levels and an ac field for microwave control between two spin levels. We observe an intricate interdependence between their spatial orientations, the externally applied strain, and the resultant efficacy in spin-state control. In most studies to date the ac and dc magnetic field orientations have been insufficiently addressed, which has led to the conclusion that strain is indispensable for the effective microwave control of heavier group-IV vacancies, such as tin- and lead-vacancy color centers. In contrast, we find that the alignment of the dc magnetic field orthogonal to the symmetry axis and the ac field parallel to it can make the application of strain obsolete for effective spin manipulation. Furthermore, we explore the implications of this field configuration on the spin's optical initialization, readout, and gate fidelities. Published by the American Physical Society 2024

Modulating metal-carrier interaction of high-loading Co-Al2O3-SiO2 catalysts for boosted N-propylcarbazole hydrogenation

We developed a series of high-loading Co-Al2O3-SiO2 catalysts to enhance the hydrogenation of N-propylcarbazole (NPCZ) by fine-tuning the Al/Si ratio. Our research reveals that adjusting this ratio can significantly modify the electronic structure of Co nanoparticles, as confirmed by XPS, H2-TPD, and CO-DRIFT analyses, thereby affecting the adsorption of hydrogen species and their interaction with unsaturated π-bonds of NPCZ intermediates. Optimal Al concentration promotes Co nanoparticles dispersion, while excessive Al leads to increased acidity and reduced surface area. The Co70/Al4Si1O catalyst, with an Al/Si ratio of 4, demonstrated superior hydrogenation efficiency by enabling fast and stable hydrogenation of NPCZ, achieving an activation energy of 64.53 kJ/mol and maintaining high performance over 10 cycles. Through DFT calculations, we explored the d-band center and Bader charge across 6 different Co10/Al-Si-O models and assessed the adsorption energies of NPCZ intermediates, along with the energetics of three stepwise reactions. The initial hydrogenation step from NPCZ to 4H-NPCZ is predominantly influenced by the catalyst's acidity/basicity, whereas the subsequent deeper hydrogenation steps of 4H-NPCZ and 8H-NPCZ are governed by the d-π feedback interaction between the metal and the adsorbate. This research offers critical guidance on selecting optimal supports for Co-based catalysts in LOHC hydrogenation.

Holographic dictionary from bulk reduction

We propose a holographic dictionary which comes from reducing the bulk theories in an asymptotically flat spacetime to its null infinity. A general boundary theory is characterized by a fundamental field, an infinite tower of descendant fields, constraints among the fundamental field and its descendants, as well as a symplectic form. For the Carrollian diffeomorphisms, we can construct the corresponding Hamiltonians which are also the fluxes from the bulk, and whose quantum operators realize this algebra with a divergent central charge. This central charge reflects the propagating degrees of freedom and can be regularized. For the spinning theory, we need a helicity flux operator to close the algebra which relates to the duality transformation. Published by the American Physical Society 2024

On Minimal Entanglement Wedge Cross Section for Holographic Entanglement Negativity

We demonstrate the equivalence of two different conjectures in the literature for the holographic entanglement negativity in AdS3/CFT2, modulo certain constants. These proposals involve certain algebraic sums of bulk geodesics homologous to specific combinations of subsystems, and the entanglement wedge cross section (EWCS) backreacted by a cosmic brane for the conical defect geometry in the bulk gravitational path integral. It is observed that the former conjectures reproduce the field theory replica technique results in the large central charge limit whereas the latter involves constants related to the Markov gap. In this context, we establish an alternative construction for the EWCS of a single interval in a CFT2 at a finite temperature to resolve an issue for the latter proposal involving thermal entropy elimination for holographic entanglement negativity. Our construction for the EWCS correctly reproduces the corresponding field theory results modulo the Markov gap constant in the large central charge limit.

Entanglement and Rényi entropies of (1+1)-dimensional O(3) nonlinear sigma model with tensor renormalization group

We investigate the entanglement and Rényi entropies for the (1+1)-dimensional O(3) nonlinear sigma model using the tensor renormalization group method. The central charge is determined from the asymptotic scaling properties of both entropies. We also examine the consistency between the entanglement entropy and the nth-order Rényi entropy with n → 1.

Petz recovery from subsystems in conformal field theory

We probe the multipartite entanglement structure of the vacuum state of a CFT in 1+1 dimensions, using recovery operations that attempt to reconstruct the density matrix in some region from its reduced density matrices on smaller subregions. We use an explicit recovery channel known as the twirled Petz map, and study distance measures such as the fidelity, relative entropy, and trace distance between the original state and the recovered state. One setup we study in detail involves three contiguous intervals A, B and C on a spatial slice, where we can view these quantities as measuring correlations between A and C that are not mediated by the region B that lies between them. We show that each of the distance measures is both UV finite and independent of the operator content of the CFT, and hence depends only on the central charge and the cross-ratio of the intervals. We evaluate these universal quantities numerically using lattice simulations in critical spin chain models, and derive their analytic forms in the limit where A and C are close using the OPE expansion. In the case where A and C are far apart, we find a surprising non-commutativity of the replica trick with the OPE limit. For all values of the cross-ratio, the fidelity is strictly better than a general information-theoretic lower bound in terms of the conditional mutual information. We also compare the mutual information between various subsystems in the original and recovered states, which leads to a more qualitative understanding of the differences between them. Further, we introduce generalizations of the recovery operation to more than three adjacent intervals, for which the fidelity is again universal with respect to the operator content.

Optical properties of negatively charged germanium-vacancy centers in detonation nanodiamonds with an average single-digit nanometer particle size

Nanodiamonds that contain germanium-vacancy centers (GeV-NDs) exhibit significant potential for biomedical and quantum science applications. GeV-NDs with an average particle size of 9 nm were recently fabricated through a detonation process that enables the practical-scale production of detonation NDs (DNDs). However, the optical properties of the GeV centers in the DNDs have not been studied thoroughly. In particular, the luminescence spectrum of these GeV-DNDs had an unassigned peak at 1.98 eV. Here, we investigate the optical properties of GeV-DNDs under various conditions. Although the GeV-DNDs exhibit a zero-phonon line (ZPL) with similar excitation energy dependence and photostability to their bulk counterparts, the ZPL linewidth is broader. The 1.98 eV-peak is attributed to a composite phonon sideband peak. The unique properties of the GeV centers in these small DNDs are explained by enhanced electron–phonon coupling.