Spin Polarization Research Articles

Dimensionality-Tailored Ferromagnetism in Quasi-Two-Dimensional MnSe2 for the Magnetoelectrochemical Hydrogen Evolution Reaction in Alkaline Media.

The application of an external magnetic field to the cathode shows great promise in facilitating the hydrogen evolution reaction (HER) via water electrolysis. However, the criteria for designing such cathodes are still under investigation. Among various aspects, understanding the effect of different magnetic states of the cathode material is crucial, especially for the HER in alkaline conditions, which possesses different reaction steps compared to that in acidic conditions. Herein, we present MnSe2 as a cathode material for the magneto-electrocatalytic HER in alkaline media, utilizing its dimension-dependent magnetic phase transition. By tailoring its dimensionality, we have achieved room-temperature ferromagnetism in its quasi-two-dimensional (2D) form, whereas its bulk counterpart exhibits paramagnetism. Upon being subjected to a low external magnetic field of 0.4 T at -182 mV (vs RHE) overpotential, quasi-2D MnSe2 exhibited a 120% improvement in current density compared to itself at zero magnetic field, while negligible changes were observed in the bulk material. This performance enhancement under a magnetic field could originate from the higher spin polarization of the ferromagnetic catalyst. This work signifies a conceptual advancement of the catalyst's spin state in magnetically enhanced electrocatalytic reaction kinetics.

First-principles calculations for intrinsic defects in MgO: Positron lifetime and momentum distribution of electron–positron pairs

We presented first-principles calculations of the formation energies for various charge states of intrinsic defects in magnesium oxide, including VO, VMg, VMg+O, VO+Mg+O, and VMg+O+Mg. These results can be used to predict their thermodynamic stability and detectability of these defects via positron annihilation spectroscopy. We employed two-component density functional theory to compute the positron annihilation properties, incorporating the effects of temperature and spin polarization. We then performed calculations of the momentum distributions of annihilating electron–positron pairs in these intrinsic defects in MgO. Using one-dimensional momentum distributions (Doppler-broadening spectra), we calculated the line-shape parameters Srel and Wrel. Our positron lifetime calculations were compared with experimental data. These research provides insight into the positron annihilation characteristics of defects in MgO.

Magnetic doping engineering in perovskite microcrystals for boosted photocatalytic CO2 reduction

Conversion of carbon dioxide into value-added chemicals through sunlight is a promising approach to reducing our reliance on fossil fuels. Spin provides another freedom to manipulate the photocatalytic CO2 reduction (CO2RR) process and enhance the corresponding properties of optoelectronic applications. In this work, improved photocatalytic CO2RR efficiency was obtained by manipulating spin-polarized species in inorganic halide perovskite microcrystals (MCs) with the introduction of manganese cations (Mn2+) and an employment of a magnetic field. Mn2+-doped CsPbBr3 MCs were prepared through self-assembly process, where Mn2+ is incorporated into CsPbBr3 matrices successfully. Introducing Mn2+ into CsPbBr3 matrices not only induces structural change but also generates new emission band as well as magnetic properties. Thereby, Mn2+-doped CsPbBr3 MCs show significantly enhanced photocatalytic CO2RR properties in contrast with pristine samples (the CO yield is significantly elevated from 22.1 to 41.9 μmol/g in Mn2+-doped CsPbBr3 MCs), as they generate spin-polarized electrons with the introduction of Mn2+. Remarkably, the photocatalytic CO2RR of Mn2+-doped CsPbBr3 MCs is greatly improved under the employment of a magnetic field, achieving 5.0 times higher performance compared to pristine CsPbBr3 MCs when the magnetic field strength is 300 mT. This enhancement is experimentally demonstrated by using magnetic circular dichroism spectroscopy. The increased photocatalytic CO2RR efficiency of Mn2+-doped CsPbBr3 MCs stems from the cooperative doping of Mn2+ and the application of magnetic fields, which generates more spin-polarized photoexcited carriers, thereby leading to extended carrier lifetime and reduced recombination process. These findings demonstrate that introducing spin into optoelectronic semiconductors is a powerful approach to enhancing photocatalytic CO2RR efficiency.

Optoelectronic and structural properties of bulk cubic perovskite RbTaO3 and surface (0 0 1) for optoelectronic and spintronics applications

We used first-principles density functional theory (DFT) to study the optical, electronic, and structural properties of RbTaO3 cubic perovskite in both bulk and surface (0 0 1) forms. The RbTaO3 bulk system exhibited semiconducting behaviour with a band gap (Eg) of 2.20 eV. It showed weak reflectivity, excellent optical conductivity, and high absorption of incident energetic photons, indicating its potential for optoelectronic applications. For the surface (0 0 1), two RbO and TaO2 terminations were constructed. We calculate the atomic displacement (ΔZ) and surface energy (Esurf) for both terminations. The RbO- and TaO2-(0 0 1) terminated surfaces appeared half-metallic ferromagnetic (HMF) with a spin magnetic moment of integer value 1.00 μβ and fully spin polarization (SP) 100 %. The Eg for RbO- and TaO2-terminations were 2.60 eV and 2.30 eV, respectively, suggesting their potential for spintronics. We also analysed and compared the optical properties and atomic populations (Q) and their variation (ΔQ) for (0 0 1)-RbTaO3 terminations with the bulk system.

Structural and Electronic Properties of the Magnetic and Nonmagnetic X0.125Mg0.875B2 (X = Nb, Ni, Fe) Materials: A DFT/HSE06 Approach to Investigate Superconductor Behavior.

MgB2 material has a simple composition and structure that is well-reported and characterized. This material has been widely studied and applied in the last 20 years as a superconductor in wire devices and storage material for H in the hydride form. MgB2 doped with transition metals improves the superconductor behavior, such as the critical temperature (T cs) or critical current (J sc) for the superconducting state. The results obtained in this manuscript indicate that Nb-, Fe-, and Ni-doping in the Mg site leads to a contraction of the unit cell through the spin polarization on the electronic resonance of the boron layer. Fe and Ni transition metals doping perturb the electronic resonance because of stronger dopant-boron bonds. The unpaired electrons are transferred from 3d orbitals to the empty 2p z orbitals of the boron atoms, locating α electrons in the σ bonds and β electrons in the π orbitals. The observed influence of magnetic dopants on MgB2 enables the proposal of an electronic mechanism to explain the spin polarization of boron hexagonal rings.

Magnetization dynamics in skyrmions due to high-speed carrier injections from Dirac half-metals.

Recent developments in the magnetization dynamics in spin textures, particularly skyrmions, offer promising new directions for magnetic storage technologies and spintronics. Skyrmions, characterized by their topological protection and efficient mobility at low current density, are increasingly recognized for their potential applications in next-generation logic and memory devices. This study investigates the dynamics of skyrmion magnetization, focusing on the manipulation of their topological states as a basis for bitwise data storage through a modified Landau-Lifshitz-Gilbert equation (LLG). We introduce spin-polarized electrons from a topological ferromagnet that induce an electric dipole moment that interacts with the electric gauge field within the skyrmion domain. This interaction creates an effective magnetic field that results in a torque that can dynamically change the topological state of the skyrmion. In particular, we show that these torques can selectively destroy and create skyrmions, effectively writing and erasing bits, highlighting the potential of using controlled electron injection for robust and scalable skyrmion-based data storage solutions.

Impact of Fe-doping on magneto-optoelectronic properties of beryllium sulfide (BeS): A first principles insight

The investigation of electronic, magnetic, structural, and optical properties of Be1-xFexS alloys is carried out by utilizing FP-LAPW method based on density functional theory (DFT) calculations. Fe-doped BeS exhibits half-metallic ferromagnetic behaviour at all doping concentrations, transforming it as favourable contender for spintronic devices. Our findings reveal the presence of 100 % spin polarization of electronic states. The calculated values of magnetic moments are 4.0, 8.0, and 16.0 μB for Be0.9375Fe0.0625S, Be0.875Fe0.125S and Be0.75Fe0.25S, respectively. The pristine BeS compound adopts a cubic close packing structure, known as the zinc blende structure, with the space group F-43m. The static values of R(0) are observed to be 0.21, 0.56, and 0.72 for Fe doped BeS at Be0.9375Fe0.0625S, Be00875Fe0.125S and Be0.75Fe0.25S, respectively. The maximum values of σ(ω) are computed as 16375.9 (1/Ω cm) for 6.25 %, 14336.5 (1/Ω cm) for 12.5 %, and 11002.1 (1/Ω cm) for 25 % Fe doped BeS. The present study unveils maximum optical absorption and conductivity in the ultraviolet (UV) region, suggesting its potential application in UV-based photovoltaic devices.

Chirality-Induced Magnetic Polarization by Charge Localization in a Chiral Supramolecular Crystal.

The chirality-induced spin selectivity (CISS) effect is a fascinating phenomenon that correlates the molecular structure with electron spin-polarization (SP). Experimental procedures to quantify the spin-filtering magnitude have extensively used magnetic-field-dependent conductive AFM. In this work chiral crystals of imide-substituted coronene bisimide ((S)-CBI-GCH) are studied to explain the dynamics of the current-voltage I - V spectra and the origin of superimposed peaks are investigated. A dynamic voltage-sweep rate-dependent phenomenon can give rise to complex I - V curves. The redox group, capable of localization of charge, acts as a localized state that interferes with the continuum of the π - π stacking, giving rise to Fano resonances. A novel mechanism for dynamic transport is introduced, which provides insight into the origin of spin-polarized charge in crystallized CBI-GCH molecules after absorption on a metallic substrate, guided by transient charge polarization. Crucially, interference between charge localization and delocalization during transport may be important properties in understanding the magnetochiral phenomena observed by electrostatic force microscopy. Finally, it is observed that charge trapping sensitively modifies the injection barrier from direct tunneling to Fowler-Nordheim tunneling transport supporting nonlinearity in CISS for this class of molecules.

A few examples of cis trans isomerization in complexes involving the oxamide function

Synthesis of heterodinuclear 3d transition metal complexes in which two metal ions are introduced in equivalent coordination sites of a ligand is quite uncommon. We have previously shown that the application of the cis–trans isomerization of the oxamido group was able to furnish such a possibility. In the present paper we demonstrate that this synthetic pathway, relying on the possibility of changing the conformation (cis vs trans) of the oxamido group, can be extended to other ligands. Although we have not been able to characterize these complexes by structural determinations, FAB-MS, EPR and magnetic data do confirm the efficiency of this reaction pathway. We also demonstrate that the cis–trans isomerization of the oxamido group is not due to a particular property of the ion involved in the reaction. In fact, isomerization is governed by the basicity of the reaction medium. According to the reaction condition, it is possible to favor or not this phenomenon, and to increase the accessibility to a larger number of novel genuine complexes. But the oxophilic character of the lanthanide ions limits the use of this synthetic pathway because it impedes this isomerization. Eventually, the very weak magnetic interactions observed in these Cu-Gd complexes can be explained thanks to spin polarization.

Spin-Degeneracy Breaking and Parity Transitions in Three-Terminal Josephson Junctions

Hybrid Josephson junctions (JJs) realized in superconductor-semiconductor heterostructures host fermionic modes known as Andreev bound states (ABSs). In these structures, a promising and yet unexplored avenue for harnessing spin and parity degrees of freedom is offered by JJs with three or more superconducting terminals, where phase-induced spin polarization and transitions of the ground state to an odd parity were predicted to arise. Here we spectroscopically probe the two-dimensional band structure of ABSs in a phase-controlled InAs/Al three-terminal JJ. Andreev bands show signatures of spin-degeneracy breaking, with level splitting in excess of ∼9 GHz, and zero-energy crossings associated to ground state fermion parity transitions. Spin splitting and parity transitions are enabled and controlled by locally applied magnetic fluxes, in the absence of Zeeman effect or Coulomb blockade. Our results underscore the potential of multiterminal hybrid devices for phase engineering ABSs, with significant implications for spin- and parity-based quantum devices. Published by the American Physical Society 2024

All-dielectric meta-surface transmission-mode ultra-thin GaAs negative electron affinity photocathode

Transmission-mode (t-mode) GaAs negative electron affinity photocathodes (NEA-PCs) can be integrated with the optical focusing lenses and microchannel plates to produce high-quality electron beams and high-sensitive detectors. Quantum efficiency (QE) of ∼40% has been reported for the t-mode thick (>1000 nm) GaAs NEA-PCs. Nevertheless, practical applications of these devices have been seriously restricted by their long response time (tens of picoseconds). In this work, the all-dielectric meta-surfaces (ADMS) were designed as the light managers for the t-mode ultra-thin GaAs NEA-PCs. For the 500–850 nm waveband, high light absorption (>80%) can be obtained through coupling the electromagnetic dipole moments of ADMS into the leaky optical modes in 100 nm ultra-thin GaAs NEA-PC layer, which leads to enhanced QE higher than that of the thick ones, the response time less than 5 ps, and the mean transverse energy less than 60 meV, respectively. Given these properties, ADMS t-model ultra-thin NEA-PCs represent a promising photocathode to provide the high-brightness short-pulse spin-polarized electron beams and high-sensitive fast-response detectors for the electron accelerator and low-light-level photodetection applications, respectively.

Inducing feature-rich electronic and magnetic properties in PtSe2 monolayer via doping with TMXn clusters (TM = Mn and Fe; X = N and P; n = 3 and 6): A first-principles study

In this work, doping with TMXn (TM = Mn and Fe; X = N and P, n = 3 and 6) clusters is proposed to modify the electronic and magnetic properties of PtSe2 monolayer. Pristine PtSe2 monolayer is a non-magnetic two-dimensional (2D) semiconductor material with indirect band gap of 1.40(2.01) eV obtained from PBE(HSE06)-based calculations. PtSe3-type multivacancies lead to the monolayer magnetization with total magnetic moment of 0.54 μB, where Pt and Se atoms around defect sites produce mainly the system magnetism. In contrast, no magnetism is induced by PtSe6-type multivacancies. The substitutional incorporation of TMXn clusters magnetizes significantly PtSe2 monolayer, where both TM and X atoms originate mainly the magnetic properties. Depending on the spin orientation in the clusters, total magnetic moments between 0.00 and 8.00 μB are obtained. All the doped DTMXn systems exhibit strong spin polarization around the Fermi level, which is derived mainly from the outermost TM-3d, N-2p, and P-3p orbitals. Consequently, either half-metallicity or magnetic semiconductor behavior can be induced, depending on the nature of TMXn cluster. Further, the Bader analysis indicates that TMNn clusters act as charge gainers due to the more electronegative nature of N atoms in comparison with Se atoms, meanwhile TMPn clusters transfer charge to the host PtSe2 monolayer. Our study may introduce the cluster doping in PtSe2 monolayer as efficient method to create new highly spin-polarized 2D materials towards spintronic applications.

First-principles calculations of structural, magneto-electronic, mechanical, optical and thermoelectric properties of novel quaternary Heusler alloys type ZrCoYAs (Y= Fe and Mn)

To determine the structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of novel quaternary Heusler alloys type ZrCoYAs (Y= Fe and Mn), we used DFT with WIEN2k. Our results showed that the ferromagnetic Y-type-III phase is more stable due to the higher negative values of their formation energy. We calculated and discussed the elastic constants Cij, which are used to calculate the mechanical properties. The Spin-polarized band structure and DOS calculations using the GGA-PBE and GGA + U approach display a metallic character. However, using the mBJ-GGA-PBE and mBJ-GGA + U approach show a half-metallic character, a semiconductor for the spin-down channel with a direct band gap of 0.61 eV with mBJ-GGA-PBE and 0.74 eV with mBJ-GGA + U for ZrCoMnAs and a direct band gap of 0.43 eV with mBJ-GGA-PBE and indirect band gap with 0.39 eV with mBJ-GGA + U for ZrCoFeAs, in contrast, the spin-up channel is metallic, with 100 % spin polarization and an integer magnetic moment of 1.00 μB for ZrCoMnAs and 2.00 μB for ZrCoFeAs, obeying the Slater-Pauling rule. The estimated Curie temperatures of ZrCoMnAs and ZrCoFeAs are 204 K using the new model, 421 K using MFA, and 385 K using the new model, 1627 K using MFA, respectively. As exchange-correlation potential, MBJ and MBJ + U provide a better description of the electronic and magnetic properties of ZrCoMnAs and ZrCoFeAs compounds. Important optical properties such as dielectric function, absorption coefficient, refractive index, optical conductivity, reflectivity, and electron energy loss function are calculated in the infrared, visible, and ultraviolet range. The static dielectric function suggests that ZrCoMnAs possesses greater polarizability. Both alloys exhibit similar behavior in the far ultraviolet region range and reach a maximum absorption in the ultraviolet range. The half-metallic character of both alloys is revealed from the reflectivity at zero frequency. The calculation of the thermoelectric properties shows positive Seebeck coefficients, indicating that these Heuslers are p-type. Furthermore, the highest power factor is observed at a temperature of 1400 K. The maximum value of ZT is ∼1.1 at 1400 K for ZrCoFeAs and ZrCoMnAs. These studies show that these alloys may have potential applications in the thermoelectric applications.

(Invited) Probing Spin Selective Surface Chemistry with Circularly Polarized XUV Light

Controlling spin states of surface reaction intermediates is an important but often overlooked parameter to designing semiconductor photocatalysts to mimic nature’s best photosynthetic complexes. Extreme Ultraviolet Reflection-Absorption (XUV-RA) spectroscopy enables direct observation of surface electron dynamics by combining element, oxidation, and spin state resolution, with surface sensitivity and ultrafast time resolution. While absorption of linearly polarized XUV light can probe the local oxidation and spin states of individual elements, it is insensitive to absolute spin alignment. To enable the study of spin-selective electron dynamics at interfaces, we have recently implemented ultrafast XUV Magnetic Circular Dichroism (XUV-MCD). Employing XUV-MCD in a reflection geometry, we are now studying the ultrafast surface electron dynamics that give rise to spin polarized photocurrents in magnetic and chiral semiconductors. As an example, yttrium iron garnet (Y3Fe5O12, YIG) is a ferrimagnetic oxide with a visible band gap, consisting of two sub-lattices based on octahedrally and tetrahedrally coordinated Fe(III) centers. Ultrafast XUV measurements show that electron-phonon coupling and polaron formation rates differ significantly between octahedral and tetrahedral centers leading to very different charge carrier recombination kinetics. Circular measurements show that this difference in recombination rate gives rise to long-lived, spin-polarized charge accumulation at the YIG surface that drives spin selective water oxidation. This new ability to observe real-time spin polarization at surfaces promises to provide key design parameters for semiconductor photocatalysts capable of spin selective surface chemistry.

Boosting Oxygen Electrocatalysis via Pre-Magnetized Multi Metallic Electrocatalyst

The quest for highly efficient durable and cost-effective electro catalysts for oxygen evolution reaction (OER) remains a pivotal focus in the advancement of renewable energy conversion technologies. Transition metal-based alkaline media electrocatalysts have emerged as promising candidates due to their versatile electronic structures and cost effectiveness. Among these, magneto-electrocatalysts, integrating magnetic properties with electrocatalytic functionalities, represent a novel frontier in OER research. In this study, we introduce a novel approach to enhance OER performance via the utilization of pre-magnetized multi-metallic (Fe-Ni-Co ) doped electrocatalysts, harnessing electron spin polarization. We tailored the electronic structure and magnetic properties of the catalyst, promoting and validating the principle of spin polarization for augmenting OER activity. Through a comprehensive experimental study, we have investigated how the inclusion of magnetic components influences the catalytic activity, stability, and overall efficiency of the electrocatalyst during OER. Experimental methodologies involving material synthesis, characterization techniques (XRD,FE-SEM, VSM study) and electrochemical analysis are employed to assess the structural, magnetic, and electrocatalytic properties of the synthesized pre-magnetised electrocatalyst.We employed the Fe-modified Nickel foam (NF) substrate as a catalyst support. Three distinct electrocatalysts (EC) [NF/Fe-Ni, NF/Fe-Co, and NF/Fe-NiCo] were electrodeposited in two different types: (electrodeposition without magnetic field) and (electrodeposition with applied magnetic field 0.6 T). Observations revealed that for all three electrocatalyst, the electrocatalysts [which were synthesized by applying a magenetic field during eletro deposition and later on OER activity was measured in the absence of magnetic field ] exhibit superior electrocatalytic activity towards OER compared to its counterparts . The highest electrocatalytic activity is provided by NF/Fe-NiCo of 0.5 mA/cm2 ECSA in the absence of a magnetic field and 0.533 mA/ cm2 ECSA in the presence of magnetic field. This is superior to that of the precious metal Ru, which has a specific activity of 0.49 mA/ cm2 ECSA at 1.5V (versus RHE). After analysing the OER performance of the catalyst, we found that the activity of NF/Fe-NiCo improved from 69.15 to 89.55 mA/ cm2 when a magnetic field was applied. Capacitance measurements (15.16% increase) and ECSA measurements (22.1% increase) also corroborated this. The overpotential measurement decreased from 243.03 mV to 239.1 mV at 100 mA/ cm2. As a result, for both sets of catalysts, the magnetic field improved the current density. Comparatively OER performance in absence of magnetic field of the electrocatalyst which was synthesized by electrodeposition with applied magnetic field was better than (for the second catalyst OER activity studied under applied magnetic field. This suggests that rather than applying a magnetic field during long-term electrolysis, one may opt to apply a magnetic field during electrocatalyst production. When we compared the OER performance of these two, we discovered that NF/Fe-NiCo exhibits the greatest activity of all catalysts at 1.5V, with 91.3 mA/ cm2, although the percentage rise is lower than that of the other catalysts. However, compared to the rise in activity, the ECSA data reveals a significant increment of 56%. The data on capacitance and overpotential likewise correspond with the current density trend. With the lowest overpotential of 236.35 mV when measured at 100 mA/cm2, the NF/NiCo catalyst performed the best overall among all the catalysts. Our findings underscore the significance of electron spin polarization in boosting electrocatalytic performance, offering a promising avenue for the design and development of advanced catalysts for sustainable energy applications and in the context of their commercial viability and integration into industrial-scale electrochemical devices.

Understanding the Reaction Activity of Ni(1-x)FexOH Towards Oxygen Evolution Reaction

The development of electrocatalysts towards the oxygen evolution reaction based on earth-abundant and cheap materials, such as transition metal oxide and hydroxide, is crucial to reduce the emission of CO2 and slowdown the global warming [1]. Among these transition metal compounds, ferromagnetic electrocatalysts usually exhibit promising activities towards OER due to their unique electron spin properties [2]. Applying an external magnetic field can further tune the electron spin polarization of ferromagnetic materials and, therefore, improve the OER activity. However, evaluating the activity of these electrocatalysts towards OER remains challenging. For example, the electrocatalysts will undergo activation under reaction conditions (frequently due to Fe insertion), which brings difficulties in determining the real reaction sites as well as establishing the “structure-activity” relationship [3]. In addition, the overall measure activity (current density) is contributed by multiple factors such as intrinsic kinetics, mass transfer, conductivity, etc., which strongly depend on operation conditions. In this talk, I will present our recent study of OER on Ni(1-x)FexOH [4]. Electrochemical impedance spectroscopy (EIS) and quasi-in situ XPS will be applied to obtain the contribution from different reaction parameters and understand the intrinsic activity.[1] McCrory, C. C. L. et al. Benchmarking Hydrogen Evolving Reaction and Oxygen Evolving Reaction Electrocatalysts for Solar Water Splitting Devices. Am. Chem. Soc. 137, 4347–4357 (2015).[2] Ren, X. et al. Spin-polarized oxygen evolution reaction under magnetic field. Commun. 12, 1–12 (2021).[3] Jung, S., McCrory, C. C. L., Ferrer, I. M., Peters, J. C. & Jaramillo, T. F. Benchmarking nanoparticulate metal oxide electrocatalysts for the alkaline water oxidation reaction. Mater. Chem. A 4, 3068–3076 (2016)[4] Wei Chen, Laura Donk, Tiago Fernandes, Anna Kitayev, ErvinTal Gutelmacher, Yury V. Kolen’ko, Marta C. Figueiredo*, in preparation.

Nuclear spin polarization of lactic acid via exchange of parahydrogen-polarized protons

Hyperpolarization has become a powerful tool to enhance the sensitivity of magnetic resonance. A universal tool to hyperpolarize small molecules in solution, however, has not yet emerged. Transferring hyperpolarized, labile protons between molecules is a promising approach towards this end. Therefore, hydrogenative parahydrogen-induced polarization (PHIP) was recently proposed as a source to polarize exchanging protons (PHIP-X). Here, we identified four key components that govern PHIP-X: adding the spin order, polarizing the labile proton, proton exchange, and polarization of the target nucleus. We investigated the last two steps experimentally and using simulations. We found optimal exchange rates and field cycling methods to polarize the target molecules. We also investigated the influence of spin relaxation of exchanging protons on the target polarization. It was found experimentally that transferring the polarization from protons directly bound to the target X-nucleus (here 13C) of lactate and methanol using a pulse sequence was more efficient than applying a corresponding sequence to the labile proton. Furthermore, varying the concentrations of the transfer and target molecules yielded a distinct maximum 13C polarization. We believe this work will further help to understand and optimize PHIP-X towards a broadly applicable hyperpolarization method.

Regulating Fe-spin state by doping P heteroatom in Fe-N-C catalyst derived from colloidal nanoparticles encapsulated ZIF-8 to boost oxygen reduction activity

Over the past decades, Fe-N-C carbon materials have been considered as one of the most ideal alternatives to the noble metal catalysts (e.g. Pt/C) for the sluggish oxygen reduction reaction (ORR) in zinc-air batteries and fuel cells. In this research, ZIF-8 cage encapsulation confinement strategy coupled with post P-doping has been employed to design porous P, N and Fe co-doped carbon (FeNC-P) for efficient oxygen reduction reaction (ORR). The zero-field cooling (ZFC) temperature-dependent magnetic susceptibility measurement revealed that incorporation of P in the Fe-N-C catalysts can induce the transition of spin polarization configuration, which promotes the desorption of *OH in the crucial step of the ORR reaction process. The best-performing FeNC-P catalyst displays a 1.00 V (vs RHE) of Eonset (onset potential) and a 0.90 V (vs RHE) of E1/2 (half-wave potential) in an alkaline solution, which exceeds the benchmark Pt/C catalyst. Moreover, it also delivers a high power density of 130 mW·cm−2 in the self-made zinc-air battery, surpassing the benchmark Pt/C catalyst (90 mW·cm−2).

Spatial electron-spin splitting in single-layered semiconductor microstructure modulated by Dresselhaus spin-orbit coupling

Abstract Combining theory and computation, we explore Goos-Hänchen effect for electron in single-layered semiconductor microstructure (SLSM) modulated by Dresselhaus spin-orbit coupling (SOC). GH displacement depends on electron spins thank to Dresselhaus SOC, therefore, electron spins can be separated from space domain and spin-polarized electrons into semiconductors can be realized. Both magnitude and sign of spin polarization ratio change with electron energy, in-plane wave vector, strain engineering and semiconductor-layer thickness. Spin polarization ratio approaches up to maximum at resonance, however, no electron-spin polarization occurs in the SLSM for zero in-plane wave vector. More importantly, spin polarization ratio can be manipulated by strain engineering or semiconductor-layer thickness, giving rise to a controllable spatial electron-spin splitter in the field of semiconductor spintronics.

Structural Chirality and Electronic Chirality in Quantum Materials

In chemistry and biochemistry, chirality represents the structural asymmetry characterized by nonsuperimposable mirror images for a material such as DNA. In physics, however, chirality commonly refers to the spin–momentum locking of a particle or quasiparticle in the momentum space. While seemingly disconnected, structural chirality in molecules and crystals can drive electronic chirality through orbital–momentum locking; that is, chirality can be transferred from the atomic geometry to electronic orbitals. Electronic chirality provides an insightful understanding of chirality-induced spin selectivity, in which electrons exhibit salient spin polarization after going through a chiral material, and electrical magnetochiral anisotropy, which is characterized by diode-like transport. It further gives rise to new phenomena, such as anomalous circularly polarized light emission, in which the light handedness relies on the emission direction. These chirality-driven effects will generate broad impacts for fundamental science and technology applications in spintronics, optoelectronics, and biochemistry.