Distinct Spin Research Articles

Design of Two-Dimensional Hybrid Perovskites with Giant Spin Splitting and Persistent Spin Textures.

Semiconductors with large energetic separation ΔE± of energy sub-bands with distinct spin expectation values (spin textures) represent a key target to enable control over spin transport and spin-optoelectronic properties. While the paradigmatic case of symmetry-dictated Rashba spin splitting and associated spin textures remains the most explored pathway toward designing future spin-transport-based quantum information technologies, controlling spin physics beyond the Rashba paradigm by accessing strategically targeted crystalline symmetries holds significant promise. In this paper, we show how breaking the traditional paradigm of octahedron-rotation based structure distortions in 2D organic-inorganic perovskites (2D-OIPs) can facilitate exceptionally large spin splittings (ΔE± > 400 meV) and spin textures with extremely short spin helix lengths (lPSH ∼ 5 nm). A simple bond angle difference captures the distortion-driven global asymmetry and correlates quantitatively with first-principles computed spin-splitting magnitudes. A multiband effective mass model that accounts for interlayer coupling provides a unified understanding of how specific symmetry elements dictate layer- and state-dependent spin polarizations within these multi-quantum-well structures. The general symmetry analysis methodology presented here, together with the potential for rationally creating 2D-OIPs with unique symmetry patterns, opens a pathway to design semiconductors with outstanding spin properties for next generation opto-spintronics.

Chirality- and Rashba- related effects in the spin texture of a two-dimensional centrosymmetric ferromagnet: The case of the CrI3 bilayer

The newly discovered two-dimensional (2D) magnetic semiconductors such as CrI3 have triggered a surge of interest stemming from their exotic spin-dependent properties and potential applications in spintronics and magneto-optoelectronics. Using first-principle density-functional-theory calculations, we investigate the properties of the spin-polarization texture in momentum space in the prototype 2D centrosymmetric ferromagnetic (FM) bilayer of CrI3 with perpendicular magnetization, with a goal of identifying general features due to interlayer interaction and their microscopic origins in 2D centrosymmetric FM materials. The FM CrI3 bilayer displays a rich in-plane spin texture in its highest valence bands. We show the existence of two distinct spin canting effects induced by the coupling of the two FM layers in establishing the in-plane spin texture. The first effect is generated by the mirror-related chirality of the layer stacking and the spin–orbit-polarized nature of the valence states, and yields the same canting on both layers. The second effect is a Rashba-related effect, which in a centrosymmetric ferromagnet induces in a single electronic state two opposite spin-canted components on the two layers, resulting in a notable frustration effect on the energy of the bonding states. Finally, we show that the above effects can be effectively used to manipulate the spin texture via compressive vertical strain, which induces in the FM CrI3 bilayer valence-band-edge states with canted spins.

Imprinted atomic displacements drive spin–orbital order in a vanadate perovskite

AbstractPerovskites with the generic composition ABO3 exhibit an enormous variety of quantum states, such as orbital order, magnetism and superconductivity. Their flexible and comparatively simple structure allows for straightforward chemical substitution and cube-on-cube combination of different compounds in atomically sharp epitaxial heterostructures. Many of the diverse physical properties of perovskites are determined by small deviations from the ideal cubic perovskite structure, which are challenging to control. Here we show that directional imprinting of atomic displacements in the antiferromagnetic Mott insulator YVO3 can be achieved by depositing epitaxial films on different facets of the same isostructural substrate. These facets were chosen such that other well-known control parameters, including lattice and polarity mismatch with the overlayer, remain nearly unchanged. We observe signatures of staggered orbital and magnetic order and demonstrate distinct spin–orbital ordering patterns on different facets. We attribute these results to the influence of specific octahedral rotation and cation displacement patterns, which are imprinted by the substrate facet, on the covalency of the bonds and the superexchange interactions in YVO3. Our results show that substrate-induced templating of lattice distortion patterns constitutes a pathway for materials design beyond established strain-engineering strategies.

Observation of doping-induced spin–orbit coupling in gold cluster assembly to carrier-tuneable semiconductors and Schottky behaviors

The doping influenced carrier dynamics to maneuvering n-type to p-type semiconducting gold cluster assembly have been assessed. The resonance photoemission spectroscopic measurements corroborate an incremental rise in the density of states at the valence edge, the overlap of valence states due to doping, and the presence of distinct spin–orbit splitting and coupling in manganese-doping (Au7Mn) compared to gold clusters (Au8), originating from the relativistic effect resulted in a semiconducting property. The work function dependent current–voltage characteristics in metal–semiconductor configuration show Ohmic and Schottky behaviors assorting p-type carriers in Au7Mn in contrast to the n-type Au8 and are presenting an atomic cluster based fast electronic device.

Probing Majorana Wave Functions in Kitaev Honeycomb Spin Liquids with Second-Order Two-Dimensional Spectroscopy.

Two-dimensional coherent terahertz spectroscopy (2DCS) emerges as a valuable tool to probe the nature, couplings, and lifetimes of excitations in quantum materials. It thus promises to identify unique signatures of spin liquid states in quantum magnets by directly probing properties of their exotic fractionalized excitations. Here, we calculate the second-order 2DCS of the Kitaev honeycomb model and demonstrate that distinct spin liquid fingerprints appear already in this lowest-order nonlinear response χ_{yzx}^{(2)}(ω_{1},ω_{2}) when using crossed light polarizations. We further relate the off-diagonal 2DCS peaks to the localized nature of the matter Majorana excitations trapped by Z_{2} flux excitations and show that 2DCS thus directly probes the inverse participation ratio of Majorana wave functions. By providing experimentally observable features of spin liquid states in the 2D spectrum, our Letter can guide future 2DCS experiments on Kitaev magnets.

Transition metal oxides: a new frontier in spintronics driven by novel quantum states and efficient charge-spin interconversion

Transition metal oxides (TMOs) have emerged as promising candidates for spintronic applications due to their unique electronic properties and novel quantum states. The intricate interplay between strong spin-orbit coupling and electronic correlations in TMOs gives rise to distinct spin and orbital textures, leading to enhanced spin-momentum locking and efficient charge-spin interconversion. Remarkably, recent researches have unveiled the significant and highly tunable nature of charge-spin interconversion efficiency in TMOs, which can be manipulated through strategies such as electric field gating, epitaxial strain, and heterostructure engineering. This review provides a comprehensive overview of the recent advances in understanding the electronic band structures of TMOs and their correlation with charge-spin interconversion mechanisms. We summarize the tunability of these properties through various experimental approaches and discuss the potential implications for spintronic device applications. The insights gained from this review can guide future research efforts towards the development of high-performance, energy-efficient spintronic devices based on TMOs.

Micromagnetic study of exchange bias effect in sub-micron dots of Co2MnSi interfaced with uncompensated IrMn

Owing to its crucial role in spintronics devices, the exchange bias (EB) phenomenon has been extensively investigated in various ferromagnet (FM) and antiferromagnet (AFM) bilayers since its discovery in Co/CoO core–shell nanoparticles. In this study, we present the emergence of negative EB for the first time in the Co2MnSi Heusler alloy interfacing with an uncompensated AFM, exhibiting analogous anisotropy to the IrMn. Due to the high pinning and IrMn anisotropy values, EB is stronger here. Investigation into the influence of ferromagnetic layer thickness (tFM) on exchange bias reveals an inverse relationship, while coercivity displays a non-monotonic increase. The analysis of spin canting angles suggests the presence of a maximum canting angle in the Co2MnSi layer close to the interface. We thoroughly analyze the spin configurations at the interface as well as away from it in the Co2MnSi (25 nm)/IrMn (5 nm) bilayer to better understand the mechanism of magnetization reversal. Interestingly, our findings unveiled distinct spin behaviors for the first and second reversals. In cases of small AFM thicknesses (tAFM), the exchange field is proportionate to the tAFM, contrasting with large tAFM, where it scales as 1/tAFM. Notably, coercivity demonstrates an increasing behavior across all tAFM variations. The angular dependence of the Heusler alloy revealed a four-fold symmetry indicative of cubic anisotropy and a two-fold symmetry representative of uniaxial anisotropy. The angular dependency study of exchange bias indicated similar clockwise (CW) and counterclockwise (CCW) rotations, with cos (θ) unidirectional dependence. However, loop shifting revealed that the lower pinning ability at 0° was due to a low Meiklejohn-Bean parameter (R) value. Additionally, through the manipulation of the R-parameter, we can tune the magnitude of the coercive field and EB. All these results are crucial for the utilization of the Co2MnSi/IrMn heterostructures for various applications in spintronics-based devices.

Cryogenic temperature magnetocaloric effect and critical behavior of GdDyErAlM (M=Fe, Co, Ni) high entropy amorphous alloys

High entropy amorphous alloys (HE AMs) have attracted extensive interest lately due to their superior magnetocaloric properties. However, the critical behavior and mechanical properties have received less research, which restricts their applications. This work presented a comprehensive investigation of the magnetocaloric effect (MCE), critical behavior, and mechanical performance of quinary Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs. All samples exhibited distinct spin glass-like behavior below TC and competitive MCE around hydrogen liquefaction temperature range. Excellent MCE was achieved by the HE AMs through a second-order phase transition from paramagnetic state to ferromagnetic state at 79 K for Fe, 41 K for Co, and 36 K for Ni. Among them, the maximum magnetic entropy change (-ΔSM)max of Gd20Dy20Er20Al20Co20 amorphous alloys was 9.59 J kg−1 K−1 under 0–5 T. Furthermore, RC and RCP of Gd20Dy20Er20Al20Fe20 amorphous alloys were respectively 519 J kg−1 and 613 J kg−1, larger than that of most RE-based amorphous alloys. For all samples, the critical behavior of the phase transition approached the mean field model, and this responded to the long-range ordering of the magnetic interaction. The bending plasticity of Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs were 0.78, 1.03, 0.89, respectively. The adjustable Tc, large (-ΔSM), high RCP, and outstanding mechanical properties suggested Gd20Dy20Er20Al20M20 (M = Fe, Co, Ni) HE AMs may find utility as magnetic refrigerants in low-temperature applications.

Superoxide to Peroxide Interconversion in Ni-TMC Complexes: The Significance of Structure and Spin States.

A deeper comprehension of the characteristics of metal-superoxide and metal-peroxide chemical species is imperative, considering their pivotal functions in oxygen transport, enzymatic activation, and catalytic oxygenations. O2 activation is mediated by the interconversion of superoxide and peroxide species. Even though there are multiple studies on metal-superoxide and -peroxide intermediates, robust examples of their interconversion processes are scarce synthetically. For example, Ni-superoxide/peroxide complexes have been characterized with N-Tetramethylated Cyclam (TMC) ligands with different ring sizes, i.e., Nickel(II)-superoxide complex is characterized with 14-TMC while Nickel(III)-peroxide complex with 12-TMC. Later, both complexes were obtained with 13-TMC ligand by employing different bases; interestingly, no evidence of interconversion between them was identified. What are the factors influencing these processes and why is this preference? We attempt a computational analysis of this issue and provide arguments based on our conclusions. 2-dimensional potential energy scan is performed on the 12-TMC, 13-TMC, and 14-TMC systems to identify the reaction path connecting superoxide and peroxide species. Analyses indicate that structure and spin states play a significant role in determining the probability of interconversion. The superoxide-peroxide interconversion process appears to be bound by their propensity for distinct structural features and spin states.

Real-time observation of coherent spin wave handedness

Magnonics, a crucial domain in information science and technology, utilizes spin waves in magnets as efficient information carriers. While antiferromagnets have been suggested for versatile magnonic platform because of the coexistence of right- and left-handed spin waves, their energetic degeneracy poses challenges for observation through spectral measurements, limiting their applicability. Recent observations of distinct spin wave handedness within the gigahertz regime have reported but, are yet to be demonstrated in terahertz (THz) frequencies of antiferromagnetic spin waves. Most of all, the coherence of spin waves is a key aspect of quantum information. Here, employing THz time-domain spectroscopy—a direct, precise, and easy probe for monitoring coherent spin wave dynamics—we discern chiral antiferromagnetic spin waves of opposite phase windings in the time domain, noting their handedness reversal across the angular momentum compensation temperature in ferrimagnets. We establish a principle for directly measuring the handedness of coherent antiferromagnetic spin waves in ferrimagnets with net magnetic moment M ≠ 0 but angular momentum L = 0. Our multidimensional access in the time and spectral domain enables the accurate determination of critical temperature and the dynamic observation of coherent chiral spin waves simultaneously in a single experiment, with potential applications in exploring other quantum chiral entities.

Exploring spin current and dielectric switching characteristics of doped-multiferroic in hexagonal phase for advance RAM technology: A theoretical study

The single-phase bismuth ferrite BiFeO3 (BFO) has garnered significant interest due to its spintronic-based switching properties observed at room temperature. The first-principles calculations were executed to examine the spin-polarized electronic, dielectric, and structural characteristics of co-doped BFO with lanthanum (La) at A-site and cobalt (Co), nickel (Ni) at B-site in its hexagonal phase (Bi1-αLaαFe1-βNiβO3 with α = β = 0.04) with generalized gradient approximation (GGA-PBE). The highest value (1.01 × 10−11 A) of total current observed in La Ni co-doped BFO, featuring a distinct spin current of the same magnitude, attributed to spin polarization at the Fermi level (100 %). Additionally, Co-doped BFO exhibits the highest observed spin current density (1.05 × 109A/m2) and charge current density (1.03 × 10−5A/m2). In case of dielectric switching properties, the Ni-doped BFO displays the lowest values of linear dielectric polarization (6.00 × 10−2 C/m2), polarization charge at its interface (1.27 × 10−17 C), capacitance (4.23 × 10−15 F), and switching energy (3.81 × 10−19 J), which is particularly lower than the reported switching energy (1.92 aJ) of multiferroic capacitor.

Loss and decoherence in superconducting circuits on silicon: Insights from electron spin resonance

Solid-state devices used for quantum computation and quantum sensing applications are adversely affected by loss and noise caused by spurious, charged two-level systems (TLS) and stray paramagnetic spins. These two sources of noise are interconnected, exacerbating the impact on circuit performance. We use an on-chip electron spin resonance (ESR) technique, with niobium nitride (NbN) superconducting resonators, to study surface spins on silicon and the effect of postfabrication surface treatments. We identify two distinct spin species that are characterized by different spin-relaxation times and respond selectively to various surface treatments (annealing and hydrofluoric acid). Only one of the two spin species has a significant impact on the TLS-limited resonator quality factor at low-power (near-single-photon) excitation. We observe a three- to fivefold reduction in the total density of spins after surface treatments and demonstrate the efficacy of ESR spectroscopy in developing strategies to mitigate loss and decoherence in quantum systems. Published by the American Physical Society 2024

New Classes of Magnetic Noise Self-Compensation Effects in Atomic Comagnetometer.

Precision measurements of anomalous spin-dependent interactions are often hindered by magnetic noise and other magnetic systematic effects. Atomic comagnetometers use the distinct spin precession of two species and have emerged as important tools for effectively mitigating the magnetic noise. Nevertheless, the operation of existing comagnetometers is limited to very low-frequency noise commonly below 1Hz. Here, we report a new type of atomic comagnetometer based on a magnetic noise self-compensation mechanism originating from the destructive interference between alkali-metal and noble-gas spins. Our comagnetometer employing K-^{3}He system remarkably suppresses magnetic noise exceeding 2 orders of magnitude at higher frequencies up to 160Hz. Moreover, we discover that the capability of our comagnetometer to suppress magnetic noise is spatially dependent on the orientation of the noise and can be conveniently controlled by adjusting the applied bias magnetic field. Our findings open up new possibilities for precision measurements, including enhancing the search sensitivity of spin-dark matter particles interactions into unexplored parameter space.

L -gap surface resonance at Pt(111): Influence of atomic structure, d bands, and spin-orbit interaction

Pt(111) hosts a surface resonance with peculiar properties concerning energy vs momentum dispersion and spin texture. At variance with the free-electron-like behavior of the L-gap Shockley-type surface states on the fcc(111) surfaces of Au, Ag, and Cu, it splits into several branches with distinct spin polarization around the center of the surface Brillouin zone Γ¯. Theoretical predictions based on density-functional theory vary depending on the particular functionals used. To clarify this issue, we investigate the atomic structure of Pt(111) by low-energy electron diffraction and the unoccupied electronic structure by spin- and angle-resolved inverse photoemission. The experimental results are backed by theoretical studies using different functionals, which show that the characteristics of the surface band depend critically on the lattice constant. From the analysis of the energy-dependent low-energy electron diffraction intensities, we derive structural parameters of the Pt(111) surface relaxation with high accuracy. In addition, we give an unambiguous definition of the nonequivalent mirror-plane directions Γ¯M¯ and Γ¯M¯′ at fcc(111) surfaces, which is consistent with band-structure calculations and inverse-photoemission data. Concerning the surface resonance at the bottom of the L gap, we identified a delicate interplay of several contributions. Lattice constant, hybridization with d bands, and the influence of spin-orbit interaction are critical ingredients for understanding the peculiar energy dispersion and spin character of the unoccupied surface resonance. Published by the American Physical Society 2024

Macroscopic tunneling probe of Moiré spin textures in twisted CrI3

Various noncollinear spin textures and magnetic phases have been predicted in twisted two-dimensional CrI3 due to competing ferromagnetic (FM) and antiferromagnetic (AFM) interlayer exchange from moiré stacking—with potential spintronic applications even when the underlying material possesses a negligible Dzyaloshinskii–Moriya or dipole–dipole interaction. Recent measurements have shown evidence of coexisting FM and AFM layer order in small-twist-angle CrI3 bilayers and double bilayers. Yet, the nature of the magnetic textures remains unresolved and possibilities for their manipulation and electrical readout are unexplored. Here, we use tunneling magnetoresistance to investigate the collective spin states of twisted double-bilayer CrI3 under both out-of-plane and in-plane magnetic fields together with detailed micromagnetic simulations of domain dynamics based on magnetic circular dichroism. Our results capture hysteretic and anisotropic field evolutions of the magnetic states and we further uncover two distinct non-volatile spin textures (out-of-plane and in-plane domains) at ≈1° twist angle, with a different global tunneling resistance that can be switched by magnetic field.

Accurate hyperfine tensors for solid state quantum applications: case of the NV center in diamond

The decoherence of point defect qubits is often governed by the electron spin-nuclear spin hyperfine interaction that can be parameterized by using ab inito calculations in principle. So far most of the theoretical works have focused on the hyperfine interaction of the closest nuclear spins, while the accuracy of the predictions for distinct nuclear spins is barely discussed. Here we demonstrate for the case of the NV center in diamond that the absolute relative error of the computed hyperfine parameters can exceed 100% using an industry standards first-principles code. To overcome this issue, we implement an alternative method and report on significantly improved hyperfine values with 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}(1%) relative mean error at all distances. The provided accurate hyperfine data for the NV center enables high-precision simulation of NV quantum nodes for quantum information processing and positioning of nuclear spins by comparing experimental and theoretical hyperfine data.

A differentiable programming framework for spin models

We introduce a novel framework for simulating spin models using differentiable programming, an approach that leverages the advancements in machine learning and computational efficiency. We focus on three distinct spin systems: the Ising model, the Potts model, and the Cellular Potts model, demonstrating the practicality and scalability of our framework in modeling these complex systems. Additionally, this framework allows for the optimization of spin models, which can adjust the parameters of a system by a defined objective function. In order to simulate these models, we adapt the Metropolis-Hastings algorithm to a differentiable programming paradigm, employing batched tensors for simulating spin lattices. This adaptation not only facilitates the integration with existing deep learning tools but also significantly enhances computational speed through parallel processing capabilities, as it can be implemented on different hardware architectures, including GPUs and TPUs.

Topological excitation of exciton-polariton half-vortices and skyrmions in a magnetic field with TE-TM splitting

We explore the topological generation of skyrmions and half-vortices in a uniform spinor exciton-polariton condensate featuring TE-TM splitting and exposed to an external magnetic field. The manipulation of pump intensity and magnetic field enables precise control over the spin texture and integrated winding number. Specifically, under an excitation condition where the power applied to the vortex state surpasses that on the non-vortex state by an amount dictated by the magnetic field, skyrmions emerge. These skyrmions exhibit a distinctive spin texture characterized by a circular polarization inversion extending from the center to the periphery. Conversely, reversing the excitation condition, where the power on the vortex state is diminished with the reversal of the magnetic field direction, leads to the creation of half-vortices across the entire condensate, devoid of any circular polarization inversion. In additional to the skyrmions and half-vortices, half-skyrmions can be also generated in the same configuration without magnetic field.

Laser‐Induced Real‐Space Topology Control of Spin Wave Resonances

AbstractFemtosecond laser excitation of materials exhibiting magnetic spin textures promises advanced magnetic control via the generation of non‐equilibrium spin dynamics. Ferrimagnetic [Fe(0.35 nm)/Gd(0.40 nm)]160 multilayers are used to explore this approach, as they host a rich diversity of magnetic textures from stripe domains at low magnetic fields, a dense bubble/skyrmion lattice at intermediate fields, and a single domain state for high magnetic fields. Using femtosecond magneto‐optics, distinct coherent spin wave dynamics are observed in this material in response to a weak laser excitation, enabling an unambiguous identification of the different magnetic spin textures. Moreover, employing strong laser excitation, versatile control of the coherent spin dynamics via non‐equilibrium transformation of magnetic spin textures becomes possible by both creating and annihilating bubbles/skyrmions. Micromagnetic simulations and Lorentz transmission electron microscopy with in situ optical excitation corroborate these findings.

Light-Controlled Multiconfigurational Conductance Switching in a Single 1D Metal-Organic Wire.

Precise control of multiple spin states on the atomic scale presents a promising avenue for designing and realizing magnetic switches. Despite substantial progress in recent decades, the challenge of achieving control over multiconfigurational reversible switches in low-dimensional nanostructures persists. Our work demonstrates multiple, fully reversible plasmon-driven spin-crossover switches in a single π-d metal-organic chain suspended between two electrodes. The plasmonic nanocavity stimulated by external visible light allows for reversible spin crossover between low- and high-spin states of different cobalt centers within the chain. We show that the distinct spin configurations remain stable for minutes under cryogenic conditions and can be nonperturbatively detected by conductance measurements. This multiconfigurational plasmon-driven spin-crossover demonstration extends the available toolset for designing optoelectrical molecular devices based on SCO compounds.