Spin Charge Research Articles

Dynamics of test particles around magnetically charged regular black holes

In this work, we have provided detailed studies of motion test neutral, photon, neutrino-like, magnetized, and magnetically charged particles around a magnetically charged regular black hole (BH) together with properties of the spacetime curvature and event horizon around the BH. In order to see differences of linear electrodynamic (LED) and nonlinear electrodynamic (NED) charge effects in these studies, we have compared all the obtained results with the results obtained in Reissner–Nordstöm (RN) BH. It has been shown that an increase of the magnetic charge causes a decrease in the curvature invariants and event horizon radius. The study of the impact parameter for photons and neutrino-like particles has shown the effect of the magnetic charge of the regular BH, stronger than the RN one. Harmonic oscillations of test particles around regular BHs are studied. As an astrophysical application of the study, we also have provided comparisons of the effects of rotating Kerr BH spin and magnetic charge of the BH on upper, [Formula: see text] and lower, [Formula: see text] frequencies of twin peak quasi-periodic oscillations (QPOs) and represented possible values of the upper and lower frequencies of the twin-peak QPOs around these BHs in various QPO models. Finally, it is shown that the effect of magnetic charge on the ISCO radius of magnetized particles becomes stronger in higher values of magnetized parameters of the magnetized particles, where the effects of RN BH and regular BH charges become distinguishable.

Single-Molecule Junction: A Reliable Platform for Monitoring Molecular Physical and Chemical Processes.

Monitoring and manipulating the physical and chemical behavior of single molecules is an important development direction of molecular electronics that aids in understanding the molecular world at the single-molecule level. The electrical detection platform based on single-molecule junctions can monitor physical and chemical processes at the single-molecule level with a high temporal resolution, stability, and signal-to-noise ratio. Recently, the combination of single-molecule junctions with different multimodal control systems has been widely used to explore significant physical and chemical phenomena because of its powerful monitoring and control capabilities. In this review, we focus on the applications of single-molecule junctions in monitoring molecular physical and chemical processes. The methods developed for characterizing single-molecule charge transfer and spin characteristics as well as revealing the corresponding intrinsic mechanisms are introduced. Dynamic detection and regulation of single-molecule conformational isomerization, intermolecular interactions, and chemical reactions are also discussed in detail. In addition to these dynamic investigations, this review discusses the open challenges of single-molecule detection in the fields of physics and chemistry and proposes some potential applications in this field.

Suppression of anisotropy of kinetic energy in doped vanadium perovskites by charged defects and spin–orbital polarons

We study the interplay of rotations of t2g-orbitals in vanadium perovskites such as La1−xSrxVO3 induced by spin–orbital polarons and by charged defects. We also analyze the resulting decay of orbital order as well as the suppression of anisotropy of kinetic energy on varying the doping. The strong local correlations and the superexchange interactions are modeled by an extended 3-orbital-flavor Hubbard–Hund model. Because of the charged defects, it is crucial to extend the model by long-range Coulomb defect potentials as well as by long-range electron–electron repulsion. Thereby, the resulting binding of doped holes (i.e., spin–orbital polarons) to negative defects leads to screening by effective dynamic dipoles. The resulting dipolar fields, in combination with disorder, control the defect states and form a soft Coulomb gap inside the Mott–Hubbard gap and thereby control the low-energy properties of the system.

Perspectives on spintronics technology development: Giant magnetoresistance to spin transfer torque magnetic random access memory

The discovery of the giant magnetoresistance (GMR) effect in 1988 started a new field called spintronics and was recognized with the 2007 Nobel Prize in Physics, which was awarded to Fert and Grunberg. Spintronics is based on the contribution of both electron spin and electron charges of materials to facilitate electronic functions, enabling one extra degree of freedom for device operations. Spintronics has grown rapidly during the past three decades with significant discoveries, technological advancements, and material and device developments that have led to numerous product applications. Furthermore, new research fields and technology areas have been discovered and continue to expand. In this Perspective, key technological advances in the field during the past three decades will be highlighted, starting with the developments that led to the first use of the GMR effect in hard disk drives and its impact in the spintronic ecosystem to currently used perpendicular magnetic tunnel junctions (pMTJs) for spin transfer torque magnetic random access memory (STT-MRAM) devices. The important aspects of the pMTJ characteristics for the application of STT-MRAM will be discussed. This Perspective will present perspectives on a new structure that enhances the efficiency of the pMTJ-based STT-MRAM and research directions that can drive further advances in spintronics.

Thermodynamic properties of two-dimensional charged spin-1/2 Fermi gases

Based on the mean-field theory, we investigate the thermodynamic properties of the two-dimensional (2D) charged spin-1/2 Fermi gas. Landé factor g is introduced to measure the strength of the paramagnetic effect. There is a competition between diamagnetism and paramagnetism in the system. The larger the Landé factor, the smaller the entropy and specific heat. Diamagnetism tends to increase the entropy, while paramagnetism leads to the decrease of the entropy. We find that there exists a critical value of Landé factor for the transition point due to the competition. The entropy of the system increases with the magnetic field when g < 0.58. With the growth of paramagnetism, when g > 0.58, the entropy first decreases with the magnetic field, then reaches a minimum value, and finally increases again. Both the entropy and specific heat increase with the temperature, and no phase transition occurs. The specific heat tends to a constant value at the high-temperature limit, and it approaches to zero at very low temperatures, which have been proved by the analytical calculation.

Electronic and magnetic correlations in quantum entanglement of 1D Extended Hubbard Model

The Hubbard model is one of the basic models in condensed matter physics. It provides a simple way to understand how electron interactions can generate very rich phase diagrams. This paper aims to study its electronic, magnetic and quantum aspects. The considered Extended Hubbard Model (EHM) is parameterized by kinetic energy t, on-ste interaction energy U, off-ste interaction energy V and exchange spin–spin interaction J.The diagonalization of the t-U-V- model allows us to study the effect of V on some local properties of the half-filled chain fermions. The behaviour of ground state energy as a function of U and V shows that this model exhibits a conductor – insulator transition near the line U=2V. While, the diagonalization of the t-U-V-J- model shows that spin–spin interaction generates a Spin Density Wave (SDW) and Charge Density Wave (CDW) separation. Moreover, to study the quantum aspect of the t-U-V-J- model, we analyse the behaviour of its quantum entanglement. The obtained results show that the quantum entanglement reach its maximum value for an optimal inter-atomic distance.

Slightly broken higher spin symmetry: general structure of correlators

We explore a class of CFT’s with higher spin currents and charges. Away from the free or N = ∞ limit the non-conservation of currents is governed by operators built out of the currents themselves, which deforms the algebra of charges by, and together with, its action on the currents. This structure is encoded in a certain A∞/L∞-algebra. Under quite general assumptions we construct invariants of the deformed higher spin symmetry, which are candidate correlation functions. In particular, we show that there is a finite number of independent structures at the n-point level. The invariants are found to have a form reminiscent of a one-loop exact theory. In the case of Chern-Simons vector models the uniqueness of the invariants implies the three-dimensional bosonization duality in the large-N limit.

Formal derivation of quantum drift-diffusion equations with spin-orbit interaction

&lt;p style='text-indent:20px;'&gt;Quantum drift-diffusion equations for a two-dimensional electron gas with spin-orbit interactions of Rashba type are formally derived from a collisional Wigner equation. The collisions are modeled by a Bhatnagar–Gross–Krook-type operator describing the relaxation of the electron gas to a local equilibrium that is given by the quantum maximum entropy principle. Because of non-commutativity properties of the operators, the standard diffusion scaling cannot be used in this context, and a hydrodynamic time scaling is required. A Chapman–Enskog procedure leads, up to first order in the relaxation time, to a system of nonlocal quantum drift-diffusion equations for the charge density and spin vector densities. Local equations including the Bohm potential are obtained in the semiclassical expansion up to second order in the scaled Planck constant. The main novelty of this work is that all spin components are considered, while previous models only consider special spin directions.&lt;/p&gt;

Spin evolution and flip in the oxygen reduction reaction: a theoretical study of Cu(Ni)XP2S6(X = In, Bi and Cr)

We found that the excellent ORR performance of Ni doped CuXP2S6(X = In, Bi and Cr) is related to spin selective charge transfer and spin flip, which are clearly observed and analyzed by first-principles calculation.

Tuning intramolecular charge transfer and spin-orbit coupling of AIE-active type-I photosensitizers for photodynamic therapy.

Development of photosensitizers (PSs) featuring type-I reactive oxygen species (ROS) with aggregation-induced emission (AIE) properties is a judicious approach to overcome the deficit of conventional photodynamic therapy (PDT). However, it remains a challenge to design AIE-active type-I ROS PSs using a simple theranostic scaffold paired with a delicate balance between intramolecular charge transfer (ICT) and large spin-orbit coupling (SOC) features to facilitate intersystem crossing (ISC) and hence to intensify triplet excitons for type-I ROS generation as well as to improve optical properties for the desired biomedical applications. In this work, a rationally designed series of PSs based on C-6-substituted tetraphenylethylene-fused benzothiazole-coumarin scaffolds, named TPE-nCUMs, were synthesized via a fused-ring-electron-acceptor (FREA) strategy, endowed with AIE properties in aqueous solution and thus self-monitoring type-I ROS generation under white-light irradiation to study the effects of diverse ICT and SOC potentials on their photochemical and optical properties. Both experimental and theoretical results revealed that the concomitantly increasing strengths of both ICT and SOC features promote type-I ROS generation by TPE-nCUMs. The key role of the SOC-promoting carbonyl group towards the ROS generation ability of TPE-nCUMs was then examined. Among TPE-nCUMs, gem-2OMe-TPE-2CUM displayed highly efficient type-I ROS generation. Importantly, gem-OMe-TPE-1CUM acts as a fluorescent indicator in HeLa cells (in vitro), revealing its excellent diffusion capability in both lysosomal and mitochondrial organelles with low dark toxicity, high cytotoxicity under white-light and remarkable PDT efficiency. Our study has thus elucidated a rationally designed strategy at the molecular level to fine-tune ICT and SOC features for the advance of AIE-active type-I ROS PSs, opening a new avenue for cancer treatment and image-guided therapy.

Magnetic field effects in non-magnetic luminescent materials: from organic semiconductors to halide perovskites

Magnetic field effects (MFEs) are used to describe the changes of the photophysical properties (including photoluminescence, electroluminescence, injectedcurrent, photocurrent, etc.) when materials and devices are subjected to the external magnetic field. The MFEs in non-magnetic luminescent materials and devices were first observed in organic semiconductor. In the past two decades, the effects have been studied extensively as an emerging physical phenomenon, and also used as a unique experimental method to explore the processes such as charge transport, carrier recombination, and spin polarization in organic semiconductors. Recent studies have found that the MFEs can also be observed in metal halide perovskites with strong spin-orbital coupling. Besides, for expanding the research domain of MFEs, these findings can also be utilized to study the physical mechanism in metal halide perovskites, and then provide an insight into the improving of the performance of perovskite devices. In this review, we focus on the magnetic field effects on the electroluminescence and photoluminescence changes of organic semiconductors and halide perovskites. We review the mainstream of theoretical models and representative experimental phenomena which have been found to date, and comparatively analyze the luminescence behaviors of organic semiconductors and halide perovskites under magnetic fields. It is expected that this review can provide some ideas for the research on the MFEs of organic semiconductors and halideperovskites, and contribute to the research of luminescence in organic materials and halideperovskites.

Spin gapless semiconductors in antiferromagnetic monolayer HC[formula omitted]N[formula omitted]BN under strain

A density functional study is presented for HC4N3BN monolayer, which is triazine g-C4N3 tailored with H at its graphitic sites and B plus N at vacant sites, under uniaxial or biaxial in-plane strain. For moderate strains up to about ±8 percent, first-principles molecular dynamics simulations prove its thermal stability at room temperature and electronic structure calculations show the persistence of antiferromagnetic ground state of the system. The material undergoes magnetic transitions to ferro- and ferrimagnetic orders respectively at the critical biaxial strain of −8.3% and uniaxial strain of 7.8%. Interestingly, both transitions occur when the electronic structures of strained systems show the character of a spin gapless semiconductor. The combined effect of spin charge transfer and band shifting is proposed as a possible explanation for these transitions. Our finding on this monolayer signifies the importance of strain engineering in designing novel materials for antiferromagnetic spintronics.

Emerging materials for spin–charge interconversion

Emerging materials for spin–charge interconversion

Oxide spin-orbitronics: spin–charge interconversion and topological spin textures

Quantum oxide materials possess a vast range of properties stemming from the interplay between the lattice, charge, spin and orbital degrees of freedom, in which electron correlations often play an important role. Historically, the spin-orbit coupling was rarely a dominant energy scale in oxides. It however recently came to the forefront, unleashing various exotic phenomena connected with real and reciprocal-space topology that may be harnessed in spintronics. In this article, we review the recent advances in the new field of oxide spin-orbitronics with a special focus on spin-charge interconversion from the direct and inverse spin Hall and Edelstein effects, and on the generation and observation of topological spin textures such as skyrmions. We highlight the control of spin-orbit-driven effects by ferroelectricity and give perspectives for the field.

Photon energy and photon behavior discussions

Photons (Solar) are the main source of energy available on Earth and provide hope of clean energy in the future, photon energy has particle characteristics, and there is an inevitable connection between the wave behavior and the particle behavior of light, in-depth understanding and exploration are required. Based on the hypothesis of the strong interaction between electrons and protons to generate photons, the energy and behaviors of photons are discussed herein. By analyzing and calculating the photon speed, the negative photon speed was found to be in excellent agreement with the existing light speed constant. The Compton effect wavelength shift was analyzed and deduced considering the interaction of positive photons and atoms, and new conclusions are drawn, proposing the reason why X-rays are positive photons. Based on existing data, the observed estimation value of the negative photon velocity shift is 0.0295 ppm. From the interaction of the spin-charged particles, the relationship between the photon wavelength and its magnetic moment was calculated. In addition, we analyzed and calculated the characteristics of photon orbits, inferred the mechanism of atomic luminescence, and qualitatively explained the phenomenon of blackbody radiation. Based on the effect of charged spin photons and the electromagnetic potential field, we explain the reason for the simultaneous existence of reflection and refraction. The relationship between the incident angle and the reflectivity was analyzed, and refractive index formulas were derived to reasonably explain the characteristics of the X-ray refractive index. As a result, edge diffraction is considered a special case of refraction. By analyzing the fluctuation of the potential field inside the atom, the diffraction phenomenon of charged particles is described, and a particle explanation of the phenomenon of light waves and beat frequencies interference is provided. It is believed that the physical model of photon charging conforms to the existing physical laws. Photon energy is kinetic energy and is derived from the potential energy of electrons or protons.

Thermodynamics of Bardeen regular black hole with generalized uncertainty principle

This study explores the emission of massive charged spin-1 particles from the background of Bardeen regular spacetime by the semi-classical method used to study the Hawking radiation spectrum. We employed the Hamilton–Jacobi method and Wentzel–Kramers–Brillouin approximation technique with the suitable form of the wave function to solve the Proca field equation. We calculated the tunneling probability of outgoing spin-1 particles and the corresponding thermodynamic temperature. Furthermore, we obtained the modified thermodynamic quantities like temperature, entropy as well as heat capacity by utilizing the quadratic form of generalized uncertainty principle (GUP) and minimal length. In the end, we investigated the local stability as well as phase transitions of the Bardeen black hole in the context of GUP-modified heat capacity.

Motion of Charged Spinning Particles in a Unified Field

Using a geometry wider than Riemannian one, the parameterized absolute parallelism (PAP) geometry, we derived a new curve containing two parameters. In the context of the geometrization philosophy, this new curve can be used as a trajectory of charged spinning test particle in any unified field theory constructed in the PAP space. We show that imposing certain conditions on the two parameters, the new curve can be reduced to a geodesic curve giving the motion of a scalar test particle or/and a modified geodesic giving the motion of neutral spinning test particle in a gravitational field. The new method used for derivation, the Bazanski method, shows a new feature in the new curve equation. This feature is that the equation contains the electromagnetic potential term together with the Lorentz term. We show the importance of this feature in physical applications.

Photoelectric and magnetic properties of boron nitride nanosheets with turbostratic structure and oxygen doping

Turbostratic and oxygen doping (3.7 atom %) hexagonal boron nitride nanosheets (TO-BNNSs) with abundant defect sites, were synthesized by pyrolyzing the mixture of melamine cyanurate and boric acid. Systematic analyses reveal a highly disordered structures and covalent oxygen-doping in the TO-BNNSs. These features endow the product with increased unpaired electrons, localized charge asymmetry and spin polarization. While compared with bulk h-BN, the optical bandgap of TO-BNNSs drop down to ∼5.2 from ∼5.7 eV, dielectric constant raised from ∼2.1 to ∼2.4, the saturation magnetic moment increased from ∼0.011 to ∼0.033 emu g−1, and the coercivity enlarged from ∼73.56 to ∼367.39 Oe. These results suggest that h-BN materials with turbostratic structure and heteroatom-doping have extensive application prospect in the fields of nanoscale optics, electronics and magnetics.

Fast Coherent Control of a Nitrogen-Vacancy-Center Spin Ensemble Using a KTaO3 Dielectric Resonator at Cryogenic Temperatures

Microwave delivery to samples in a cryogenic environment can pose experimental challenges such as restricting optical access, space constraints and heat generation. Moreover, existing solutions that overcome various experimental restrictions do not necessarily provide a large, homogeneous oscillating magnetic field over macroscopic lengthscales, which is required for control of spin ensembles or fast gate operations in scaled-up quantum computing implementations. Here we show fast and coherent control of a negatively charged nitrogen vacancy spin ensemble by taking advantage of the high permittivity of a KTaO3 dielectric resonator at cryogenic temperatures. We achieve Rabi frequencies of up to 48 MHz, with the total field-to-power conversion ratio $C_{\rm P} = $ 9.66 mT/$\sqrt{\rm W}$ ($\approx191$ MHz/$\sqrt{\rm W}$). We use the nitrogen vacancy center spin ensemble to probe the quality factor, the coherent enhancement, and the spatial distribution of the magnetic field inside the diamond sample. The key advantages of the dielectric resonator utilised in this work are: ease of assembly, in-situ tuneability, a high magnetic field conversion efficiency, a low volume footprint, and optical transparency. This makes KTaO3 dielectric resonators a promising platform for the delivery of microwave fields for the control of spins in various materials at cryogenic temperatures.

The foundation of the hyperunified field theory I — Fundamental building block and symmetry

Starting from the motional property of functional field based on the action principle of path integral formulation while proposing maximum coherence motion principle and maximum locally entangled-qubits motion principle as guiding principles, we show that such a functional field as fundamental building block appears naturally as an entangled qubit-spinor field expressed by a locally entangled state of qubits. Its motion brings about the appearance of Minkowski space–time with dimension determined by the motion-correlation [Formula: see text]-spin charge and the emergence of [Formula: see text]-spin/hyperspin symmetry as fundamental symmetry. Intrinsic [Formula: see text]-spin charge displays a periodic feature as the mod 4 qubit number, which enables us to classify all entangled qubit-spinor fields and space–time dimensions into four categories with respect to four [Formula: see text]-spin charges [Formula: see text]. An entangled decaqubit-spinor field in 19-dimensional hyper-space–time is found to be a hyperunified qubit-spinor field which unifies all discovered leptons and quarks and brings on the existence of mirror lepton–quark states. The inhomogeneous hyperspin symmetry [Formula: see text] as hyperunified symmetry in association with inhomogeneous Lorentz-type symmetry [Formula: see text] and global scaling symmetry provides a unified fundamental symmetry. The maximum locally entangled-qubits motion principle is shown to lay the foundation of hyperunified field theory, which enables us to comprehend long-standing questions raised in particle physics and quantum field theory.