Showing papers on "Exchange interaction published in 2022"
TL;DR: In this article , the authors extended the Monte Carlo method to investigate the thermodynamic and magnetocaloric properties of the graphdiyne bilayer under the presence of the external magnetic field.
14 citations
TL;DR: In this paper , the authors find an electron doping dependent variation of magnetic orders of a 2D AFM insulator NiPS3, where doping concentration is tuned by intercalating various organic cations into the van der Waals gaps of NiPS-3 without introduction of defects and impurity phases.
Abstract: To electrically control magnetic properties of material is promising toward spintronic applications, where the investigation of carrier doping effects on antiferromagnetic (AFM) materials remains challenging due to their zero net magnetization. In this work, the authors find electron doping dependent variation of magnetic orders of a 2D AFM insulator NiPS3, where doping concentration is tuned by intercalating various organic cations into the van der Waals gaps of NiPS3 without introduction of defects and impurity phases. The doped NiPS3 shows an AFM-ferrimagnetic (FIM) transition at a doping level of 0.2–0.5 electrons/cell and a FIM-AFM transition at a doping level of ≥0.6 electrons/cell. The authors propose that the found phenomenon is due to competition between Stoner exchange dominated inter-chain ferromagnetic order and super-exchange dominated AFM order at different doping level. The studies provide a viable way to exploit correlation between electronic structures and magnetic properties of 2D magnetic materials for realization of magnetoelectric effect.
12 citations
TL;DR: In this article , the authors synthesize m-body spin exchange Hamiltonians with m up to 5 in a superconducting quantum circuit by simultaneously exciting multiple independent qubits with time-energy correlated photons generated from a qudit.
Abstract: Synthesizing many-body interaction Hamiltonians is a central task in quantum simulation. However, it is challenging to synthesize Hamiltonians that have more than two spins in a single term. Here we synthesize m-body spin-exchange Hamiltonians with m up to 5 in a superconducting quantum circuit by simultaneously exciting multiple independent qubits with time-energy correlated photons generated from a qudit. The dynamic evolution of the m-body interaction is governed by the Rabi oscillation between two m-spin states, in which the states of each spin are different. We demonstrate the scalability of our approach by comparing the influence of noises on the three-, four- and five-body interaction and building a many-body Mach-Zehnder interferometer which potentially has a Heisenberg-limit sensitivity. This study paves a way for quantum simulation involving many-body interaction Hamiltonians such as lattice gauge theories in quantum circuits.
6 citations
6 citations
5 citations
TL;DR: In this paper , the authors investigated the origin of possible magnetism in the monolayer family of triangular lattice materials and found that the spin-orbit coupling (SOC) can be effectively tuned through the ligand elements as 3$d$ transition metal ions do not strongly contribute to the anisotropic component of the inter-site exchange interaction.
Abstract: Motivated by the recent wealth of exotic magnetic phases emerging in two-dimensional frustrated lattices, we investigate the origin of possible magnetism in the monolayer family of triangular lattice materials $MX_2$ ($M$={V, Mn, Ni}, $X$={Cl, Br, I}). We first show that consideration of general properties such as filling and hybridization enables to formulate trends for the most relevant magnetic interaction parameters. In particular, we observe that the effects of spin-orbit coupling (SOC) can be effectively tuned through the ligand elements as the considered 3$d$ transition metal ions do not strongly contribute to the anisotropic component of the inter-site exchange interaction. Consequently, we find that the corresponding SOC matrix-elements differ significantly from the atomic limit. In a next step and by using two complementary approaches based on first principles, we extract realistic effective spin models and find that in the case of heavy ligand elements, SOC effects manifest in anisotropic exchange and single-ion anisotropy only for specific fillings.
4 citations
TL;DR: In this paper, a two-dimensional Cr2O3 monolayer with Curie temperature up to 460 K and 100% spin polarization has been designed for spintronic devices.
4 citations
TL;DR: In this article , the role of selfinteraction error (SIE) removal on the evaluation of magnetic exchange coupling constants was examined and the effect of scaling down the self-interaction correction (SIC) for three nonempirical density functional approximations (DFAs) namely, the local spin density approximation, the Perdew-Burke-Ernzerhof generalized gradient approximation, and the recent SCAN family of meta-GGA functionals.
Abstract: We examine the role of self-interaction error (SIE) removal on the evaluation of magnetic exchange coupling constants. In particular, we analyze the effect of scaling down the self-interaction correction (SIC) for three nonempirical density functional approximations (DFAs) namely, the local spin density approximation, the Perdew-Burke-Ernzerhof generalized gradient approximation, and the recent SCAN family of meta-GGA functionals. To this end, we employ three one-electron SIC methods: Perdew-Zunger SIC [Perdew, J. P.; Zunger, A. Phys. Rev. B, 1981, 23, 5048.], the orbitalwise scaled SIC method [Vydrov, O. A. et al. J. Chem. Phys. 2006, 124, 094108.], and the recent local scaling method [Zope, R. R. et al. J. Chem. Phys. 2019, 151, 214108.]. We compute the magnetic exchange coupling constants using the spin projection and nonprojection approaches for sets of molecules composed of dinuclear and polynuclear H···He models, organic radical molecules, and chlorocuprate and compare these results against accurate theories and experiment. Our results show that for the systems that mainly consist of single-electron regions, PZSIC performs well, but for more complex organic systems and the chlorocuprates, an overcorrecting tendency of PZSIC combined with the DFAs utilized in this work is more pronounced, and in such cases, LSIC with kinetic energy density ratio performs better than PZSIC. Analysis of the results in terms of SIC corrections to the density and to the total energy shows that both density and energy correction are required to obtain an improved prediction of magnetic exchange couplings.
4 citations
3 citations
TL;DR: In this article , the impurity levels and exchange interaction between magnetic impurities in graphene driven by an off-resonant circularly polarized light field were investigated, and it was shown that a dynamical band gap opens up at the Dirac point, allowing impurities levels to exist inside the gap, which gives rise to a resonance feature in the exchange energy for impurities located either at the same or different sublattices.
Abstract: We theoretically investigate the impurity levels and exchange interaction between magnetic impurities in graphene driven by an off-resonant circularly polarized light field. Our analysis captures the non-perturbative effects resulting from scattering with magnetic impurities with a strong onsite potential. Under irradiation, a dynamical band gap opens up at the Dirac point, allowing impurity levels to exist inside the gap. These impurity levels are shown to give rise to a resonance feature in the exchange energy for impurities located either at the same or different sublattices. The exchange interaction also shows a wider spatial range of antiferromagnetic behavior due to irradiation. Our work demonstrates that the exchange energy of magnetic impurities in graphene is extensively tunable by light irradiation in the presence of strong potential scattering.
3 citations
TL;DR: In this article , a comprehensive model for a description of magnetization processes in rare-earth tetraborides (RET) is presented, which is based on the coexistence of two subsystems, and namely, the spin subsystem described by the XXZ Heisenberg model and the electronic subsystem describing by the generalized Hubbard model on the Shastry-Sutherland lattice.
TL;DR: In this article , the extended Heisenberg Hamiltonian for the atomic dimer with spin S = 1 is diagonalized exactly, and the ground state properties of the dimer are studied numerically in a wide range of Hamiltonian parameters, including energy spectrum, biquadratic moment, residual entropy, ground-state phase diagrams and magnetization curves.
TL;DR: In this article , the influence of the crystalline and electronic structure of the material on its magnetic properties is focused on, especially on the exchange interactions among magnetic ions, and methods of determination of the exchange parameters are described by using different experimental techniques, such as measurements of magnetic susceptibility, magnetization, and specific heat.
Abstract: Diluted magnetic semiconductors (DMS) are interesting because of the interplay between the electronic and magnetic subsystems. Selected magnetic properties of IV–VI DMS are described, looking at the similarities and differences between magnetic properties of II–VI, IV–VI, and III–V DMS. The influence of the crystalline and electronic structure of the material on its magnetic properties is focused on, especially on the exchange interactions among magnetic ions. Methods of determination of the exchange parameters are described by using different experimental techniques, such as measurements of magnetic susceptibility, magnetization, and specific heat. The development in the material technology from bulk crystals to thin films and nanostructures is followed.
TL;DR: In this article , a rigorous kinetic model of the irreversible reaction between the spin-1/2 and spin- 1 particles in an encounter complex with the reactive doublet state was considered.
Abstract: The kinetics of spin-selective reactions involving triplet molecules, such as triplet-triplet annihilation or electron transfer to dioxygen molecules in the ground triplet spin state, are strongly dependent on the dipole-dipole interaction (DDI) of electron spins in spin-1 particles. The effect of this interaction on the intersystem crossing in the reaction encounter complex of the paramagnetic particles was previously considered for some particular cases using oversimplified approaches. In this study, we consider a rigorous kinetic model of the irreversible reaction between the spin-1/2 and spin-1 particles in an encounter complex with the reactive doublet state. This model explicitly includes both isotropic exchange coupling of the reactants and spin dependence of the reaction rate in the form of the Haberkorn reaction term. For the time-independent DDI, an analytical expression for the reaction kinetics was derived. The effect of DDI fluctuations was analyzed using numerical simulations. It was found that increasing both the exchange coupling and the reaction rate constants can significantly slow down the quartet-doublet spin transitions and, as a consequence, the observed spin-selective reaction rate. Additionally, the presence of the irreversible reaction in the doublet states affects a coherent evolution in the non-reactive quartet subsystem.
TL;DR: In this paper, the current-induced spin polarization (CISP) of charge carriers is studied theoretically in symmetric quantum wells growing in [001] crystallographic direction, where both k-linear and k-cubed Dresselhaus spin-orbit interactions are present.
Abstract: The current-induced spin polarization (CISP) of charge carriers is one of the main mechanisms of spin-to-charge interconversion effects that can be used in new spintronics devices. Here, CISP is studied theoretically in symmetric quantum wells growing in [001] crystallographic direction, where both k -linear and k -cubed Dresselhaus spin–orbit interactions are present. The exchange interaction responsible for perpendicular to plane net magnetization is also taken into account. The main focus is on the influence of cubic Dresselhaus term on CISP and the interplay between spin–orbit interaction (SOI) and the exchange field. The analytical and numerical results are derived within the linear response theory and Matsubara Green’s function formalism. Apart from detailed numerical results, we also provide some analytical expressions that may be useful for interpretation of experimental results and for characterization of quantum wells with Dresselhaus SOI. Analytical expressions for the relevant Berry curvature are also derived, and it is shown that the Berry curvature in magnetic 2DEG with cubic Dresselhaus interaction oscillates in the k -space, while its averaged value is reduced. We also analyze the temperature behavior of CISP and calculate the low-temperature spin polarizability due to heat current.
TL;DR: In this article , the phase diagrams and magnetic properties of a ferromagnetic/antiferromagnetic Ising nanoparticles assembly with the spin-1/2 core and spin-3/2 shell were analyzed.
TL;DR: In this paper , the effect of spin reversal on temperature dependences of the total magnetization during crossing the compensation point for different applied fields has been investigated in a framework of quantum-mechanical mean field theory.
TL;DR: In this article , the authors analyzed the dynamics of an interstitial defect in the Wigner crystal and showed that it produces local ferromagnetism with much higher energy scales.
Abstract: The two-dimensional Wigner crystal (WC) occurs in the strongly interacting regime (r_{s}≫1) of the two-dimensional electron gas (2DEG). The magnetism of a pure WC is determined by tunneling processes that induce multispin ring-exchange interactions, resulting in fully polarized ferromagnetism for large enough r_{s}. Recently, Hossain et al. [Proc. Natl. Acad. Sci. U.S.A. 117, 32244 (2020)PNASA60027-842410.1073/pnas.2018248117] reported the occurrence of a fully polarized ferromagnetic insulator at r_{s}≳35 in an AlAs quantum well, but at temperatures orders of magnitude larger than the predicted exchange energies for the pure WC. Here, we analyze the large r_{s} dynamics of an interstitial defect in the WC, and show that it produces local ferromagnetism with much higher energy scales. Three hopping processes are dominant, which favor a large, fully polarized ferromagnetic polaron. Based on the above results, we speculate concerning the phenomenology of the magnetism near the metal-insulator transition of the 2DEG.
TL;DR: In this paper , a singlet-triplet qubit defined by four-electron states in the double-quantum-dot system was studied and it was shown that the exchange energy as a function of detuning can be non-monotonic, suggesting existence of sweet spots.
Abstract: The exchange interaction in a singlet-triplet qubit defined by two-electron states in the double-quantum-dot system ("two-electron singlet-triplet qubit") typically varies monotonically with the exchange interaction and thus carries no sweet spot. Here we study a singlet-triplet qubit defined by four-electron states in the double-quantum-dot system ("four-electron singlet-triplet qubit"). We demonstrate, using configuration-interaction calculations, that in the four-electron singlet-triplet qubit the exchange energy as a function of detuning can be non-monotonic, suggesting existence of sweet spots. We further show that the tuning of the sweet spot and the corresponding exchange energy by perpendicular magnetic field can be related to the variation of orbital splitting. Our results suggest that a singlet-triplet qubit with more than two electrons can have advantages in the realization of quantum computing.
TL;DR: In this article , the structure of ground state exciton of Cd(Se,Te) quantum dots embedded in ZnTe matrix is studied experimentally using photoluminescence spectroscopy and theoretically using configuration interaction methods.
Abstract: The structure of the ground state exciton of Cd(Se,Te) quantum dots embedded in ZnTe matrix is studied experimentally using photoluminescence spectroscopy and theoretically using ${\bf k}\cdot{\bf p}$ and configuration interaction methods. The experiments reveal a considerable reduction of fine-structure splitting energy of the exciton with increase of Se content in the dots. That effect is interpreted by theoretical calculations to originate due to the transition from spatially direct (type-I) to indirect (type-II) transition between electrons and holes in the dot induced by increase of Se. The trends predicted by the theory match those of the experimental results very well.The theory identifies that the main mechanism causing elevated fine-structure energy in particular in type-I dots is due to the multipole expansion of the exchange interaction. Moreover, the theory reveals that for Se contents in the dot $>0.3$, there exist also a {\bf peculiar type of confinement showing signatures of both type~I and type~II} and which exhibits extraordinary properties, such as almost purely light hole character of exciton and toroidal shape of hole states.
TL;DR: In this article, a theory describing spatiotemporal behavior of spin transport in two-band metals by postulating a spin-exchange interaction between electrons and holes was developed, which revealed two types of electron-hole coupled-spin transport modes: a dissipative mode and a nonissipative mode with an infinite spin diffusion length.
Abstract: We develop a theory describing spatiotemporal behavior of spin transport in two-band metals by postulating a spin-exchange interaction between electrons and holes. Starting with the semiclassical Boltzmann equation, we derive a system of coupled diffusion equations and solve them analytically under steady-state conditions. The solutions reveal two types of electron-hole coupled-spin transport modes: a dissipative mode and a nondissipative mode with an infinite spin diffusion length. The two modes are the manifestations of two types of spin coupling channels. Besides the exchange interaction, we incorporate into our derivation the relaxation caused by the spin-orbit interaction to show how it affects the spin transport characteristics of the two modes.
TL;DR: In this paper , a theoretical study of exchange couplings in double Perovskite La2CuMnO6, using Monte Carlo simulation, is presented, based on the relation between the internal energy and the magnetization per site in the framework of Ising model.
TL;DR: In this paper , the exchange coupling between an antiferromagnet (AF) and a rare-earth (RE) was explored within Mn3Ir/Dy bilayers for two different Dy thicknesses.
TL;DR: In this article , a first-principles microscopic theory of multipolar exchange interaction between $J$-multiplets in $f$ metal compounds has been developed and applied to the description of the ground-state order in neodymium nitride with rocksalt structure.
Abstract: In insulating lanthanides, unquenched orbital momentum and weak crystal-field (CF) splitting of the atomic $J$ multiplet at lanthanide ions result in a highly ranked (multipolar) exchange interaction between them and a complex low-temperature magnetic order not fully uncovered by experiment. Explicitly correlated {\it ab initio } methods proved to be highly efficient for an accurate description of CF multiplets and magnetism of individual lanthanide ions in such materials. Here we extend this {\it ab initio } methodology and develop a first-principles microscopic theory of multipolar exchange interaction between $J$-multiplets in $f$ metal compounds. The key point of the approach is a complete account of Goodenough's exchange mechanism along with traditional Anderson's superexchange and other contributions, the former being dominant in many lanthanide materials. Application of this methodology to the description of the ground-state order in the neodymium nitride with rocksalt structure reveals the multipolar nature of its ferromagnetic order. We found that the primary and secondary order parameters (of $T_{1u}$ and $E_g$ symmetry, respectively) contain non-negligible $J$-tensorial contributions up to the ninth order. The calculated spin-wave dispersion and magnetic and thermodynamic properties show that they cannot be simulated quantitatively by confining to the ground CF multiplet on the Nd sites. Our results demonstrate that the {\it ab initio } approach to the low-energy Hamiltonian represents a powerful tool for the study of materials with complex magnetic order.
TL;DR: In this article , an analytical and numerical solution of the spin anisotropic Kondo lattice for arbitrary dimension at half filling has been provided in the framework of the mean field approach, where the ground state in the insulator state is determined by a static [Formula: see text] field of local moments.
Abstract: In the framework of the mean field approach, we provide analytical and numerical solution of the spin-[Formula: see text] anisotropic Kondo lattice for arbitrary dimension at half filling. Nontrivial solution for the amplitude of the field opens a gap in the fermion spectrum of an electron liquid in which local moments on the lattice sites are realized. The ground state in the insulator state is determined by a static [Formula: see text] field of local moments, which forms the lattice with a double cell, conduction electrons move in this field. Due to hybridization between electron states a large Fermi surface is formed in the Kondo lattice. A gap in the quasi-particle spectrum is calculated depending on the magnitudes of exchange integrals for the simple lattices with different dimension. The proposed approach is also valid for describing the Kondo lattice with weak anisotropy of the exchange interaction, which makes it possible to study the behavior of the spin-[Formula: see text] Kondo lattice with an isotropic exchange interaction.
TL;DR: In this article , the authors proposed that the giant EB in Mn3.5Au0.5N originates from the global interaction between two magnetic sublattices.
TL;DR: In this paper , the intrinsic magnetic topological insulator MnBi2Te4 (MBT) provides a platform for the creation of exotic quantum phenomena, but the design of stable magnetic structures remains challenging.
Abstract: The intrinsic magnetic topological insulator MnBi2Te4 (MBT) provides a platform for the creation of exotic quantum phenomena. Novel properties can be created by modification of the MnBi2Te4 framework, but the design of stable magnetic structures remains challenging. Here we report ferromagnet-intercalated MnBi2Te4 superlattices with tunable magnetic exchange interactions. Using molecular beam epitaxy, we intercalate ferromagnetic MnTe layers into MnBi2Te4 to create [(MBT)(MnTe)m]N superlattices and examine their magnetic interaction properties using polarized neutron reflectometry and magnetoresistance measurements. Incorporation of the ferromagnetic spacer tunes the antiferromagnetic interlayer coupling of the MnBi2Te4 layers through the exchange-spring effect at MnBi2Te4/MnTe hetero-interfaces. The MnTe thickness can be used to modulate the relative strengths of the ferromagnetic and antiferromagnetic order, and the superlattice periodicity can tailor the spin configurations of the synthesized multilayers. The magnetic exchange interaction of MnBi2Te4—an intrinsic magnetic topological insulator—can be tuned by intercalating ferromagnetic layers of MnTe.
TL;DR: In this article , the sensitivity of tiny Ni-doping on magnetic properties of magnetoelectric CaBaCo4O7 was investigated and it was shown that Ni substitution leads to disorder and disturbs the exchange interactions which could be responsible for competing magnetic state and broadening of magnetic transition in the doped samples.
TL;DR: In this paper , a weak antiferromagnetic interaction mediated by a non-covalent interaction was identified by magnetometry measurements, and the exchange magnitude (J = -2.24 cm−1, J stands for isotropic magnetic exchange constant) was determined.