High Spin Research Articles

Integrable structure of higher spin CFT and the ODE/IM correspondence

We study two dimensional systems with extended conformal symmetry generated by the W\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{W} $$\\end{document}3 algebra. These are expected to have an infinite number of commuting conserved charges, which we refer to as the quantum Boussinesq charges. We compute the eigenvalues of the quantum Boussinesq charges in both the vacuum and first excited states of the higher spin module through the ODE/IM correspondence. By studying the higher spin conformal field theory on the torus, we also calculate thermal correlators involving the energy-momentum tensor and the spin-3 current by making use of the Zhu recursion relations. By combining these results, we show that it is possible to derive the current densities, whose integrals are the quantum Boussinesq charges. We also evaluate the thermal expectation values of the conserved charges, and show that these are quasi-modular differential operators acting on the character of the higher spin module.

Investigation of high spin properties of $$^{55}$$Cr in deformed Hartree–Fock and angular momentum projection model

Investigation of high spin properties of $$^{55}$$Cr in deformed Hartree–Fock and angular momentum projection model

Constraining Spacetime Dimensions in Quantum Gravity by Scale Invariance and Electric–Magnetic Duality

Abstract We consider a low-energy effective theory of p-branequaes in a D-dimensional spacetime, and impose two conditions: (1) the theory is scale-invariant, and (2) the electric–magnetic dual $(D-p-4)$-branes exist and they obey the same type of interactions to the p-branes. (We also assume other natural conditions such as Lorentz invariance but not string theory, supersymmetry, supergravity, and so on.) We then ask what values of p and D are consistent with these conditions. Using simple dimensional analysis, we find that only two solutions are possible: $(p,D)=(2,11)$ and $(p,D)=(2n-1,4n+2)$, ($n=1,2,3,\cdots$). The first solution corresponds to M-theory, and the second solutions at $n=1$ and $n=2$ correspond to self-dual strings in little string theory and D3-branes in type IIB superstring theory, respectively, while the second solutions for $n \ge 3$ are unknown but would be higher spin theories. Thus, quantum gravity (massless spin two theory) satisfying our two conditions would only be superstring theories, and the conditions would be strong enough to characterize superstring theories in quantum gravity.

Gravitational wave fluxes on generic orbits in near-extreme Kerr spacetime: Higher spin and large eccentricity

Gravitational wave fluxes on generic orbits in near-extreme Kerr spacetime: Higher spin and large eccentricity

Probing the geometric and electronic structure of rhodium oxide clusters (RhO)n− (n = 2–4) by anion photoelectron spectroscopy and theoretical calculations

The cluster configurations of (RhO)n− (n = 2–4) have been examined using photoelectron (PE) velocity-map imaging combined with density functional theory calculations. The PE spectra have provided the anion detachment energies (ADEs) information of three ground states, determined to be 2.40, 2.86, and 2.94 eV for n = 2–4, respectively. The geometric structures have been identified by comparing the density of states (DOS) spectra of several low-lying isomers with the PE spectra. The three cluster configurations consist of a Rhn (n = 2–4) core with isolated O atoms bonded to the core, exhibiting planar or quasi-planar geometries. The analysis of magnetic moments and spin densities indicated that the most stable three anions have high spin multiplicities of 4, 5, and 4 for n = 2–4, respectively, with the unpaired electrons delocalized on each of the Rh and O atoms.

Spin state driven weighted mobility and thermal conductivity properties of electron (Hf) doped strongly correlated Mott insulator LaCoO3 for thermoelectric applications

Here, we report the temperature-dependent electrical resistivity and thermopower of hole (Sr) and electron (Hf) doped LaCoO3 in the range of 303–753 K. With increasing temperature, the insulating behavior (303–503 K) with dominance of small polaron hopping to metallic transition (>503 K) is observed. The electron doped sample shows an insulating behavior (19.5 Ω cm) and positive thermopower (139 μV K−1) value due to the spin state blockade, i.e., electron hopping from high spin Co2+ to low spin Co3+ is strongly inhibited. The calculated weighted mobility (μW) of 0.01 to 0.96 cm2 V−1 s−1 validates the observed spin blockade mechanism in electron doped LaCoO3. The fluctuation of spin/orbital ordering and point defect scattering results in the low thermal conductivity of 0.5 W m−1 K−1 for Hf doped LaCoO3. The spin state blockade observed in the electrical resistivity and low lattice thermal conductivity reveals that spin state transition drives the thermoelectric response in Mott insulator LaCoO3.

High polarization sensitivity passive spin Photogalvanic devices based on 2D perovskite CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction

In recent years, Dion-Jacobson (D-J) perovskite has been extensively studied. In order to further study the application of D-J perovskite materials in spin-optoelectronic multifunctional devices, this paper is based on CsSbCl3Br and CsMnBr4, a zero-band gap semi-metallic material with the same ferromagnetic ground state and the same crystal structure. In this paper, put forward with transverse CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction optoelectronic devices. The characteristics of photocurrent are discussed using parallel configuration (PC) and anti-parallel configuration (APC) magnetoelectric poles under two conditions: vertical incidence of linearly polarized light and elliptically polarized light utilizing density functional theory and the non-equilibrium Green’s function method. The results reveal that the device can achieve complete spin polarization photocurrent, pure spin current, perfect spin filtering effect, and excellent spin valve effect, with high extinction ratios. Under linearly polarized light, the maximum extinction ratio reaches 2747 for the PC configuration and 5200 for the APC configuration. For elliptically polarized light, the extinction ratio is 739 for the PC configuration and reaches a maximum of 240 for the APC configuration. These results indicate that the lateral CsMnBr4/CsSbCl3Br/CsMnBr4 heterojunction has broad multi-functional application prospects in the field of optoelectronics and spintronics.

Ni–Ca metastable–nonmetastable bimetallic sites induced ·OH directed generation and efficient water purification

AbstractStrongly oxidizing ·OH can non‐selectively degrade various organic pollutants, but how to selectively generate ·OH is a great challenge. In this study, the directed generation of ·OH was achieved based on Ni–Ca metastable–nonmetastable bimetallic sites, Ni2+/Ni3+ valence cycling provided electrons for ·OH generation induced by the non‐variable Ca‐based sites, which constructed a nearly 100% selective generation pathway of ·OH (O3 → HO3/HO2 → OH). The antibiotic pefloxacin could be completely removed in 15 min, and the COD removal efficiency for other hard‐to‐degrade pollutants such as oxalic acid and chlorobenzoic acid could reach more than 90%. Ni doping significantly increased the oxygen vacancy and Lewis acid content, and DFT calculations showed that Ni–Ca dual‐site had a lower reaction energy barrier and the complexed hydroxyl radical intermediate *OO had a higher spin density (−0.6), which was more favorable for the generation of ·OH. Therefore, this study provides new ideas for efficient treatment of actual wastewater.

Intrinsic and extrinsic relaxation mechanisms for controlling spin current intensity in Fe 100−x Co x /Ta bilayers

Controlling the damping parameter in metallic ferromagnetic thin films is a key step for spintronic applications in which spin currents are generated by spin pumping. The coexistence of two states with low and high damping constant values would allow to obtain states of high and low spin current intensity, respectively. We have fabricated Fe 100−x Co x /Ta (with nominal x = 0, 15, 20, 25, 30 and 35) bilayers in which the Fe 100−x Co x layers grow epitaxially and the Ta layer is polycrystalline. We have found the coexistence of Gilbert damping and two magnon scattering mechanisms linked to a sign change in the magnetocrystalline anisotropy constant that allows the manipulation of low and high intensity states of the measured inverse spin Hall effect voltage. Bilayers with lower Co concentrations ( x⩽ 25%) present different relaxation mechanisms (isotropic Gilbert damping and two magnon scattering) and an extra ferromagnetic resonance linewidth broadening produced due to mosaicity. Bilayers with Co concentration x> 25% present a dominating Gilbert damping for all directions in the film plane. However, in this concentration range the damping constant is anisotropic and when the magnetic field is applied along the hard magnetization direction α increases ∼420% with respect to the value obtained for the easy magnetization direction. Coexistence of isotropic Gilbert damping and two magnon scattering generated spin currents 2.5 times larger when the field is applied along the hard magnetization axis compared to the value observed in the easy magnetization axis. Thesefindings make the Fe 100−x Co x /Ta system an excellent candidate for spintronic device applications.

Low spin solutions of higher spin gravity: BPST instanton

Higher spin gravities do not have a low energy limit where higher-spin fields decouple from gravity. Nevertheless, it is possible to construct fine-tuned exact solutions that activate low-spin fields without sourcing the higher-spin fields. We show that BPST (Belavin-Polyakov-Schwartz-Tyupkin) instanton is an exact solution of Chiral Higher Spin Gravity, i.e. it is also a solution of the holographic dual of Chern-Simons matter theories. This gives an example of a low-spin solution. The instanton sources the opposite helicity spin-one field and a scalar field. We derive an Effective Field Theory that describes the coupling between an instanton and the other two fields, whose action starts with the Chalmers-Siegel action and has certain higher derivative couplings.

The 2018 Outburst of MAXI J1820+070 as Seen by Insight-HXMT

We present an analysis of the whole 2018 outburst of the black hole X-ray binary MAXI J1820+070 with Insight-HXMT data. We focus our study on the temporal evolution of the parameters of the source. We employ two different models to fit the disk’s thermal spectrum: the Newtonian model diskbb and the relativistic model nkbb. These two models provide different pictures of the source in the soft state. With diskbb, we find that the inner edge of the disk is close to the innermost stable circular orbit of a fast-rotating black hole and the corona changes geometry from the hard to the soft state. With nkbb, we find that the disk is truncated in the soft state and that the coronal geometry does not change significantly during the whole outburst. However, the model with nkbb can predict an untruncated disk around a fast-rotating black hole if we assume that the disk inclination angle is around 30° (instead of ∼60°, which is the inclination angle of the jet and is usually adopted as the disk inclination angle in the literature) and we employ a high-density reflection model. In such a case, we measure a high value of the black hole spin parameter with observations in the soft state, in agreement with the high spin value found from the analysis of the reflection features and in disagreement with the low spin value found by previous continuum-fitting method measurements with the disk inclination angle set to the value of the jet inclination angle.

Hexagonal core-shell structure nanowire with high spins of spin-3/2 and spin-5/2

Hexagonal core-shell structure nanowire with high spins of spin-3/2 and spin-5/2

Systematically Revisiting All NuSTAR Spins of Black Holes in X-Ray Binaries

We extend our recent work on black hole spin in X-ray binary systems to include an analysis of 189 archival NuSTAR observations from 24 sources. Using self-consistent data reduction pipelines, spectral models, and statistical techniques, we report an unprecedented and uniform sample of 36 stellar-mass black hole spin measurements based on relativistic reflection. This treatment suggests that prior reports of low spins in a small number of sources were generally erroneous: our comprehensive treatment finds that those sources tend to harbor black holes with high spin values. Overall, within 1σ uncertainty, ∼86% of the sample are consistent with a ≥ 0.95, ∼94% of the sample are consistent with a ≥ 0.9, and 100% are consistent with a ≥ 0.7 (the theoretical maximum for neutron stars; a = cJ/GM 2). We also find that the high-mass X-ray binaries (those with A-, B-, or O-type companions) are consistent with a ≥ 0.9 within the 1σ errors; this is in agreement with the low-mass X-ray binary population and may be especially important for comparisons to black holes discovered in gravitational wave events. In some cases, different spectra from the same source yield similar spin measurements but conflicting values for the inclination of the inner disk; we suggest that this is due to variable disk winds obscuring the blue wing of the relativistic Fe K emission line. We discuss the implications of our measurements, the unique view of systematic uncertainties enabled by our treatment, and future efforts to characterize black hole spins with new missions.

Strong homotopy algebras for chiral higher spin gravity via Stokes theorem

Chiral higher spin gravity is defined in terms of a strong homotopy algebra of pre-Calabi-Yau type (noncommutative Poisson structure). All structure maps are given by the integrals over the configuration space of concave polygons and the first two maps are related to the (Shoikhet-Tsygan-)Kontsevich Formality. As with the known formality theorems, we prove the A∞-relations via Stokes’ theorem by constructing a closed form and a configuration space whose boundary components lead to the A∞-relations. This gives a new way to formulate higher spin gravities and hints at a construct encompassing the known formality theorems.

Earth-catalyzed detection of magnetic inelastic dark matter with photons in large underground detectors

Inelastic dark matter with moderate splittings, O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(few to 150) keV, can upscatter to an excited state in the Earth, with the excited state subsequently decaying, leaving a distinctive monoenergetic photon signal in large underground detectors. The photon signal can exhibit sidereal-daily modulation, providing excellent separation from backgrounds. Using a detailed numerical simulation, we examine this process as a search strategy for magnetic inelastic dark matter with the dark matter mass near the weak scale, where the upscatter to the excited state and decay proceed through the same magnetic dipole transition operator. At lower inelastic splittings, the scattering is dominated by moderate mass elements in the Earth with high spin, especially 27Al, while at larger splittings, 56Fe becomes the dominant target. We show that the proposed large volume gaseous detector CYGNUS will have excellent sensitivity to this signal. Xenon detectors also provide excellent sensitivity through the inelastic nuclear recoil signal, and if a future signal is seen, we show that the synergy among both types of detection can provide strong evidence for magnetic inelastic dark matter. In the course we have calculated nuclear response functions for elements relevant for scattering in the Earth, which are publicly available on GitHub.

Spin stiffness and spin excitation gap of van der Waals ferromagnetic Fe3+δGeTe2

Fe3+δGeTe2 (FGT) has proved to be an interesting van der Waals (vdW) ferromagnetic compound with a tunable Curie temperature ( TC ). However, the underlying mechanism for varying TC remains elusive. Here, we systematically investigate and compare low-temperature magnetic properties of single crystalline FGT samples that exhibit TC s ranging from 160 K to 205 K. Spin stiffness (D) and spin excitation gap (Δ) are extracted using Bloch’s theory for crystals with varying Fe content. Compared to Cr-based vdW ferromagnets, FGT compounds have higher spin stiffness values but lower spin wave excitation gaps. We discuss the implication of these relationships in Fe–Fe ion magnetic interactions in FGT unit cells. The itinerancy of magnetic electrons is measured and discussed under the Rhodes–Wohlfarth ratio (RWR) and the Takahashi theory.

Regulating Fe(III) spin state by anchoring iron on titanium dioxide for enhancing photo-Fenton treatment of tetracycline wastewater

Tetracycline (TC) wastewater can hardly be treated effectively by conventional processes due to its stable chemical structure and its refractoriness to biodegradation. Photo-Fenton technology based on iron-based catalyst exhibits excellent capacity on organic wastewater treatment, but current iron-based catalyst materials exist crucial problems such as slow regeneration of Fe(II) and low utilization of H2O2. In this study, Fe atom was anchored on TiO2 to regulate the spin state of Fe to prepare a new efficient photo-Fenton material. The results showed that the removal of TC by Fe2O3-TiO2(high spin, HS) can reach 94.7%, while the removal of TC by Fe-TiO2(low spin, LS) was only 83.0%. The Fe2O3-TiO2(HS) maintained high photo-Fenton activity after five cycles, and the TC removal rate still reached 91.8%. Fe2O3-TiO2(HS) had a narrow bandgap and excellent photogenerated charge separation properties, which facilitates the generation of photogenerated charges, improves the electron transfer, and accelerates the redox cycle of Fe(III)/Fe(II). The electrons in the 3d orbital of Fe2O3-TiO2(HS) are more easily to cross the antibonding orbital of the H2O2, which is conducive to the adsorption of H2O2 and generation of ·OH to accelerate TC degradation. This study provides a new photo-Fenton material for the treatment of TC wastewater and offers a new strategy for the development of photo-Fenton.

Why high spin? Why sulphur? Comparative analysis of catalytic oxidation by Compound I of cytochrome P450, catalase, peroxidase, and selenocysteine-modified P450

Compound I, which is formed in the catalytic cycle of cytochrome P450 enzymes, is best described as a high-spin state (S = 3/2) rather than a low-spin state (S = 1/2). Its high-spin role in catalytic oxidation (R−H → R−OH) remains poorly understood (why high spin?). Catalase and peroxidase can both generate Compound I. The axial ligand of cysteine thiolate R−S− (P450) at the haem site may be responsible for P450′s unique catalytic oxidation, as opposed to tyrosinate R−O− (catalase) or histidine imidazolate R−N− (peroxidase) or selenocysteine selenolate R−Se− (why sulphur?). This study aimed to address these two questions by density functional theory calculations (PBE-D3BJ-gCP/def2-SVP) of the reactions between Compound I and CH4. The results indicate that the stability of the adducts X−Fe−OH–-–CH3 (where X = Se, S, O, and N), which are produced from abstracting H from CH4 by X−Fe=O, can provide insights into these two issues.

Preparation of LiLaZrMO (M= Ga/Al) solid electrolytes for thermal batteries

Thermal batteries (TBs) are ideal power sources for high temperature environment due to their high specific energy, long storage time, and quick activation. However, the common molten salt electrolytes (MSE) suffer from overflow under overload or high spin state, which could lead to short circuit of the batteries. To address this issue, LiLaZrMO (LLZMO, M = Ga/Al) doped with different elements are prepared. The doping elements result in the phase change of LiLaZrO (LLZO) from tetragonal to cubic, alters the distribution of Li atoms and increases the ion transport bottleneck sizes. In particular, LiLaZrGaO (LLZGO) has the lowest activation energy (0.3 eV) and the highest total conductivity (2.57 × 10−2 S cm−1 at 500 °C) owing to the larger bottleneck and unique Li+ transport channel. TB with LLZGO provides the highest discharge specific capacity of 368.5 mAh g−1 and lowest internal resistance (0.23 Ω cm−2). Compared with the ones using LiF–LiCl–LiBr MSE, TB with LLZGO solid electrolyte (SE) also shows superior performance in pulse discharge capabilities due to the stable internal resistance as well as the fluctuation free characteristics. Therefore, LLZGO SE holds great potential as viable alternative to MSEs in TBs.

Importance of Spin Channels from Radical-Radical Reactions in Hydrogen-Oxygen Combustion Mechanisms at High Temperatures.

Radical-radical reactions can generate two channels with high and low spins. In this work, ten radical-radical reactions with different spin channels and four radical-molecule reactions in hydrogen-oxygen combustion were systematically investigated from a theoretical perspective. The potential energy surface (PES) of radical-radical reactions reveals that the high- and low-spin states of the reactant are energetically degenerate and the two channels are energetically feasible. The difference in rate constants between the high- and low-spin channels gradually decreases as the temperature increases. Then, the kinetic parameters of the 14 bimolecular reactions in the hydrogen-oxygen mechanism of the University of California, San Diego (UCSD), were replaced to simulate the ignition delay time and laminar flame speed. The simulation results agree well with the available experimental findings, indicating the necessity of considering both high- and low-spin channels for kinetic simulation.