Spin-polarized Carriers Research Articles

Proximity-Induced Exchange Interaction and Prolonged Valley Lifetime in MoSe2/CrSBr Van-Der-Waals Heterostructure with Orthogonal Spin Textures.

Heterostructures, composed of semiconducting transition-metal dichalcogenides (TMDC) and magnetic van-der-Waals materials, offer exciting prospects for the manipulation of the TMDC valley properties via proximity interaction with the magnetic material. We show that the atomic proximity of monolayer MoSe2 and the antiferromagnetic van-der-Waals crystal CrSBr leads to an unexpected breaking of time-reversal symmetry, with originally perpendicular spin directions in both materials. The observed effect can be traced back to a proximity-induced exchange interaction via first-principles calculations. The resulting spin splitting in MoSe2 is determined experimentally and theoretically to be on the order of a few meV. Moreover, we find a more than 2 orders of magnitude longer valley lifetime of spin-polarized charge carriers in the heterostructure, as compared to monolayer MoSe2/SiO2, driven by a Mott transition in the type-III band-aligned heterostructure.

Hole and electron spin lifetime in lightly n-doped silicon at low temperatures

We report on photoinduced inverse spin-Hall effect (ISHE) measurements as a function of the incident photon energy in the 4–50 K temperature range for a Pt/n-doped Si junction. Optical spin injection allows generating a spin-oriented population of electrons and holes around the Δ valleys and Γ point of the Si Brillouin zone, respectively. Spin-polarized carriers cross the Pt/Si contact and then enter the Pt overlayer, where spin-to-charge conversion occurs by means of spin-dependent scattering with Pt nuclei. For temperatures T up to 20 K, most of the dopants are not ionized, so that the electric field, stemming from the contact potential between Pt and Si, extends to the whole Si substrate, which becomes insulating, and only spin-oriented holes reach the Pt layer and contribute to the ISHE spectra. For T>20 K, donors are partially ionized, and the resulting space charge close to the Pt/Si interface leads to the formation of a Schottky contact where the electric field rapidly vanishes within a few micrometers. As a consequence, also spin-polarized electrons enter Pt by means of thermionic emission, contributing to the ISHE signal. We numerically solve the one-dimensional spin drift-diffusion equations for holes and electrons and estimate the temperature dependence of the spin lifetime in Si for both populations, demonstrating that Si may serve as a versatile platform for spintronic applications, able to leverage both electrons and holes.

Full-zone optical spin injection in AlxGa1−xAs alloys

Abstract Full-zone optical spin injection in Al x Ga1−x As alloys is investigated by analyzing the degree of circular polarization (DCP) of luminescence in a quantum well architecture. Aluminium content in AlGaAs barrier layers is varied to explore both the direct- and indirect-bandgap regimes. For all the samples, experimental data are compared with a 30-band k .p model addressing the band structure of the alloy and the optical spin injection over the entire Brillouin zone. We observe circularly polarized luminescence arising from the spin generation either around Γ or the L valley. We interpret the specific shape of the DCP within a framework accounting for smaller electron spin relaxation at the higher k points of the X valley of the AlGaAs barrier layer. Moreover, it is found that the presence of strain plays a vital role in governing the magnitude and shape of the DCP spectra for near band-edge excitation while exciting spin-polarized carriers in the direct-bandgap AlGaAs. We believe that these findings are important for the realization of AlGaAs-based spin-photonic devices aiming at possible applications in quantum technology.

Spin filtering and quantum transport with transition metal-doped hydrogenated silicon quantum dot

Spin filtering is a fundamental operation in spintronics, enabling the generation and detection of spin-polarized carriers. Here, we proposed and theoretically demonstrated that a 3d transition metal (TM) doped hydrogenated silicon quantum dot (TM:H-SiQD) is a suitable candidate for spin-filter devices. Using density functional theory, we investigate the structure, electronic properties, and magnetic behavior of TM:H-SiQD. Our calculations demonstrate that Mn:H-SiQD exhibits the highest stability. The designed spin-filter device using Mn:H-SiQD shows a spin-filtering efficiency of 99.9% at 300 K electrode temperature along with very high conductance. This remarkable efficiency positions it as a promising candidate for spintronic devices.

Thin Ga(Sb,P)/GaP quantum wells with indirect band gap: Crystal structure, energy spectrum, exciton recombination and spin dynamics

Heterostructures with thin GaSb layers embedded in a GaP matrix are studied by transmission electron microscopy as well as steady-state and transient photoluminescence. For a single, one monolayer thick deposition with subsequent overgrowth, nonmonotonic Sb segregation results in self-organized Ga(Sb,P) double-quantum well (QW) formation. One QW is positioned deep in GaP at the designated place according to the heterostructure design, and the other QW is in the near surface region after 40 monolayers of GaP overgrowth. Both QWs are characterized by an indirect band gap. The band alignment in the QWs is identified as type I. In spite of the long (up to milliseconds) exciton lifetimes in the QWs in combination with the electron g factor of +2, the emission of the QWs demonstrates a low circular polarization degree in longitudinal magnetic fields as strong as 10 T. We demonstrate that the electron spin polarization in the Ga(Sb,P)/GaP heterostructure subject to a magnetic field occurs in the GaP layer, and spin-polarized charge carriers captured in the QWs store their spin orientation up to the millisecond time range, indicating very long spin relaxation times for the strongly localized electrons in the Ga(Sb,P)/GaP QWs.

Origin of Dopant-Carrier Exchange Coupling and Excitonic Zeeman Splitting in Mn2+-Doped Lead Halide Perovskite Nanocrystals.

Low-dimensional metal halide perovskites have unique optical and electrical properties that render them attractive for the design of diluted magnetic semiconductors. However, the nature of dopant-exciton exchange interactions that result in spin-polarization of host-lattice charge carriers as a basis for spintronics remains unexplored. Here, we investigate Mn2+-doped CsPbCl3 nanocrystals using magnetic circular dichroism spectroscopy and show that Mn2+ dopants induce excitonic Zeeman splitting which is strongly dependent on the nature of the band-edge structure. We demonstrate that the largest splitting corresponds to exchange interactions involving the excited state at the M-point along the spin-orbit split-off conduction band edge. This splitting gives rise to an absorption-like C-term excitonic MCD signal, with the estimated effective g-factor (geff) of ca. 70. The results of this work help resolve the assignment of absorption transitions observed for metal halide perovskite nanocrystals and allow for a design of new diluted magnetic semiconductor materials for spintronics applications.

First-principles calculations and experimental studies on Cr2MnAl Heusler alloy nanoparticles for spintronics applications

In depth understanding of the magnetic, structural and electrical properties of Heusler alloys are crucial to achieve potential applications in spin-based device. Wherein, we report the synthesis of Cr2MnAl Heusler alloy nanoparticles (NPs) via co-precipitation method and also demonstrated their transport properties. Interestingly X-ray analysis confirms the cubic phase of the synthesized Heusler alloy NPs and transmission electron microscopy (TEM) analysis reveals that the Cr2MnAl as particle size of 10 ± 2 nm. Moreover, this particle size has adverse effect on symmetry of Cr2MnAl Heusler alloy due to their higher surface to volume ratio that significantly changes their magnetic and electrical properties. These NPs exhibit soft ferromagnetic properties with a Curie temperature (Tc) of 25 K. Besides, resistivity measurements indicate the semiconducting nature and also we report the observation of anomalous Hall effect. In addition, we support our experimental results by studying the electronic and magnetic properties of alloy using first principle calculations. This density functional theory reveals that Cr2MnAl has half metallic characteristics with high spin polarization. In light of above, this material can be used as intermediate layer to decouple the two ferromagnetic layers which acts as spin-polarized carriers in spin-based device.

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.

Quantum anomalous Hall effect and half-metal state of valley in VGe2N4 monolayer

Understanding the physical properties of valley and achieving its half metal state is the key to applying the valley degree of freedom. In this study, by first-principles calculations, the VGe2N4 monolayer is demonstrated as a ferrovalley semiconductor with a valley polarization of 48 meV. Furthermore, two means of compressive strain and regulating the electron correlation effect are explored to achieve the half-metal state of valley in the present VGe2N4 monolayer. Interestingly, topological phase transitions from ferrovalley, half-valley metal to quantum anomalous Hall effect state appear with the increase of strain in the VGe2N4 monolayer. More interestingly, half-metal state of valley induced by electronic correlation or strain can occur in VGe2N4 monolayer, which means 100% spin-polarized valley carriers will be excited. In this case, with the action of an in-plane electric field, the VGe2N4 monolayer will present an anomalous valley Hall effect. Based on these results, the related valleytronics devices are designed. Our work emphasizes the entire process from ferrovalley to topological phase transition, and a method for achieving the half-metal state of valley is proposed. Our finding is of great significance for the development of valleytronics.

Probing the metallic state, magnetic anisotropy, and large Curie temperature in CaCuFeReO[formula omitted]: Strain engineering

Rhenium-based double perovskite oxides (DPOs) are a particularly fascinating class of materials because of high carrier spin polarization, large magnetic anisotropy energy (MAE), and complex electrical behavior along with high Curie temperature (TC). Herein, we discussed the impact of biaxial ([110]) strain ranging from −5% to ＋ 5% along the ab-plane on the electronic and magnetic properties of CaCuFeReO6 (CCFRO) DPO using ab-inito calculations. The unstrained system exhibits a ferrimagnetic (FiM) spin ordering as an energetically stable magnetic ground state due to electron hopping between Fe+3/Re+5t2g and Cu+2eg orbitals along with a metallic electronic state. Moreover, [010] (b-axis) is the magnetic easy axis that produces the MAE of 5.36 meV, giving a giant MAE constant of 1.97×107 erg/cm3. The evaluated partial spin-magnetic moment on the Cu1/Cu2/Fe/Re ion is 0.14/0.44/4.04/−0.64μB, where “−” sign on the Re moment means that its spin is antiparallel to the other ions, verifying the FiM ordering in the system. Also, the eg, t2g/eg, and t2g orbital characteristics of Cu+2, Fe+3, and Re+5 ions are visible in the spin-magnetization density iso-surfaces plots, respectively. Using the classical Heisenberg model, the computed TC for the unstrained structure is 576 K, which is quite close to the experimentally reported value of 567 K. In addition, it is shown that the FiM metallic behavior in the motif is robust against biaxial ([110]) strain within the considered range. It has also been revealed that TC increased to 5.73%/3.30% for the considered range of −5% compressive/＋5% tensile strain due to improved structural distortions.

Half Metallic Properties of the Polymorphs of Rubidium Selenide Compound

Half-metallic ferromagnets denote a specific category of compounds where one spin channel exhibits a gap at the Fermi level, contrasting with the metallic nature of the other spin channel. This distinction results in complete carrier spin polarization, reaching 100% at the Fermi level. A first-principles pseudopotential plane-wave method is utilized to examine the structural, electronic, and magnetic characteristics of RbSe across various polymorphs. Our investigation covers the RbSe compound in the CsCl (B2), NaCl (B1), ZnS (B3), NiAs (B81) and wurtzite (B4) phases. The calculations were done using the quantum ESPRESSO code within the generalized gradient approximation. The lattice parameters, bulk moduli, and their pressure derivatives agrees with prior theoretical data for cubic structures. The electronic band structures and density of states indicate the emergence of half-metallic and magnetic properties in RbSe, which stem from the existence of spin-polarized p orbitals within the Se atom. RbSe shows half-metallic behaviour in all structures studied with an integer magnetic moment of 1μB per formula unit for CsCl, NaCl, ZnS; and 2μB for NiAs and wurtzite. Results showed that most energetically stable phase of all five crystal structures studied is the CsCl-type of RbSe.

Tautomerization Makes Topological Phase Transition in 2D Organometallic Lattices

AbstractThe investigation into approaches for achieving reversible control of topological phase transitions has attracted substantial research interest. So far, several system‐dependent physical control methods are developed, while a chemical strategy for efficient regulation of topological properties is still lack. Here, this study presents a chemical means to achieve reversible topological control in 2D organometallic lattices by introducing the lactam‐lactim tautomerization modules in the organic linkers. The strategy is validated in the theoretically designed 2D hexagonal framework with planar tricoordinated Co as nodes and 2,2′‐bithiazole derivatives as organic linkers, which transforms from a ferrimagnetic half metal with a local gap featuring Chern number of +1 to a ferromagnetic Chern insulator possessing Chern number of −1 after lactam‐lactim tautomerization. Simultaneously, a flip in the spin polarization of charge carriers between the two lattice tautomers is also observed.

ZnxFe3-xO4–ZnO heterojunction interfaced with poly(L-DOPA) electron transfer mediator layer for enhanced visible light photocatalytic activity

Z-scheme heterojunctions comprising ZnxFe3-xO4@poly(L-DOPA)@ZnO (ZF@PD@ZnO) were synthesized using solvothermal and precipitation techniques. The study aimed to investigate the impact of the poly(L-DOPA) electron transfer mediator on the photocatalytic performance of ZnxFe3-xO4@ZnO (ZF@ZnO) nanocomposites under visible light irradiation. X-ray diffraction (XRD) and HRTEM analysis confirmed the formation of heterostructures, identifying the crystalline phases of both ZnO and zinc ferrite. BFTEM images revealed a polyhedral shape for all samples, with a tendency toward mild agglomeration. The partial inversion of the zinc ferrite cubic spinel structure was evidenced by FT-IR, XPS, and VSM analyses. Zinc ferrite was found to be ferromagnetic, with cation distributions between tetrahedral (A) and octahedral (B) positions as [Zn0.62+Fe0.43+]A[Fe0.42+Fe1.63+]BO4. The samples exhibited notable photocatalytic activity against Rhodamine B, serving as a model contaminant. Furthermore, the stability and reusability of the samples were examined. Additionally, the study elucidated the photocatalytic mechanism produced by the ternary Z-scheme ZF@PD@ZnO, involving spin-polarized charge carriers. Energy band alignment was evaluated by combining ultraviolet photoelectron spectroscopy (UPS) with UV-Vis spectroscopy. The interplay between band alignment and reactive oxygen species (ROS) generation was discussed in correlation with EPR results. Enhanced ROS generation under visible light illumination, observed in the ZF@PD@ZnO nanocomposite, is mainly due to the addition of the conductive poly(L-DOPA) layer, acting as an electron transfer mediator in the Z-scheme heterojunction, ensuring enhanced charge separation.

Enhanced room-temperature magnetic field effect on spin-polarized excitons of cesium lead bromine-magnetite nanocomposites

The generation and manipulation of spin-polarized electrons are the basis of spintronic applications. Spin injection from a ferromagnetic surface or heterojunction to a semiconductor adjacent layer is often used to create spin-polarized carriers; however, for halide perovskites, due to the mismatch of lattice parameters with most ferromagnets at room temperature, this spin injection is challenging. In this study, we synthesize all-inorganic perovskite CsPbBr3 surrounded by Fe3O4 magnetic nanoparticles. It is found that this nanocomposite shows both magnetization and magnetic field-induced circularly polarized photoluminescence at room temperature. Specifically, with the attachment of Fe3O4 nanoparticles closely on the surface of CsPbBr3 nanocrystals, both the degree of circular polarization and g-factor enhanced by 3.5 times compared with that of pure CsPbBr3. The phenomenon should be due to the formation of exciton magnetic polaron through the coupling of the magnetic aligned nanoparticles with the excitonic state of the host semiconductor in the external magnetic field. The effective spin injection provides a method of controlling the excitonic spin polarization of all-inorganic halide perovskites for spintronic applications.

Emergent carrier spin polarization in (Fe, Al)-codoped ZnO thin films explored by Andreev Reflection spectroscopy

The carrier spin polarization of magnetic materials is one of the most critical elements for current-driven spintronics devices. Experimental evidence of spin polarization of magnetic oxides is still a matter of considerable debate although room-temperature ferromagnetism was reported in nearly all doped/undoped oxides materials. In this work, we systematically study the carrier spin polarization and non-uniform magnetization scattering of Zn1−xFexAl0.01O (x = 0.05, 0.10) thin films in metallic regime. Spin polarization 65 ± 8% is confirmed experimentally for Zn0.95Fe0.05Al0.01O by Andreev Reflection spectroscopy, which reduces to 40 ± 5% for Zn0.90Fe0.10Al0.01O as Fe doping level increases to 10%. Magnetoresistance and Anomalous Hall effect are observed in Zn1−xFexAl0.01O films which corroborates the spin-polarized carrier in spin-split bands close to the Fermi level. Furthermore, combining element mapping and Andreev reflection spectra, our results support that non-uniform magnetization of Zn1−xFexAl0.01O films which introduces large inelastic spin-flip scattering at the interface of Zn1−xFexAl0.01O/Pb superconducting junctions, and consequently reduction of spin polarization. The spin-polarized carrier and transport behaviors in Zn1−xFexAl0.01O magnetic oxides provide the reliable evidence to identify the intrinsic ferromagnetism and an excellent platform for spintronics device applications.

Computational design of the novel Fe-doped single-layer SrS: structural, electro-magnetic, and optical properties.

The search for novel intrinsic two-dimensional (2D) magnetic materials is crucial to understand the fundamentals of 2D magnetism and realize next-generation magneto-electric and magneto-optical systems. Using the rigorous framework of spin-polarized density functional theory (SPDFT)-based ab initio calculations, this investigation systematically investigates the effects of a stepwise change in the Fe composition (x) on the structural, electro-magnetic and optical properties of the ordered SrS based single-layer alloys, with x encompassing values from 0 to 1. Our comprehensive analysis revealed that the calculated formation energies, cohesive energies, phonon dispersions, molecular dynamics, and elastic constants of both bare SrS and FeS monolayers indicate their thermodynamic, dynamic, thermal, and mechanical stability in hexagonal and square structures, respectively. Significantly, the introduction of magnetic Fe dopants into the non-magnetic SrS semiconductor enabled the creation of an intrinsic magnetic (FM) state characterized by spin-polarized charge carriers at the Fermi level (E F). As doping increases, the electronic structure shows a noticeable dependence on the chemical composition. It is noteworthy that the systems doped with 0.750 and 1 Fe exhibit metallic-magnetic and metallic non-magnetic properties, respectively, and the rest are half-semiconductors (HSC) according to the GGA approximation. Conversely, the HSE approach shows a transition to HSC for a doping level of 0.750, while others maintain the same behavior. The study of the optical properties shows improvements compared to the bare SrS monolayer through the incorporation of Fe dopants. The bare SrS has light absorption in the ultraviolet region, while the absorption band edges for HSC compounds change from the infrared to visible regions. This study proposes a practical method to tune the properties of the SrS single-layer by selectively adjusting the dopant concentration. Such control is promising for applications in spintronics and optical based nanodevices.

(Invited) Quest for Fully Spin and Optically Polarized Semiconductor Nanostructures for Room-Temperature Opto-Spintronics

Spintronics represents a new paradigm for future electronics, photonics and information technology, which explores the spin degree of freedom of the electron for information storage, processing and transfer. Since 1990s, we have witnessed great success of metal-based spintronics that has revolutionized the mass data storage industry. There has also been an enormous push for semiconductor spintronics during the past three decades, with the aim to capitalize the past and current success of charge-based semiconductor technology and to make its spin counterpart the backbone of future spintronics just like semiconductors have done in today’s electronics/photonics. An exclusive advantage of semiconductor spintronics is its potential for opto-spintronics that will allow integration of spin-based information processing and storage with photon-based information transfer and communications. Unfortunately, progresses of semiconductor spintronics have so far been severely hampered by the failure to generate nearly fully spin-polarized charge carriers in semiconductors at and above room temperature (RT) at which today’s devices operate.In this work, we succeed to achieve conduction electron spin polarization exceeding 90% at RT in a semiconductor nanostructure, which remains steadily high even up to 110°C [1]. This represents the highest RT electron spin polarization ever reported in any semiconductor by any approach! This breakthrough is accomplished by a conceptually new approach of defect-engineered remote spin filtering and amplification of InAs quantum-dot (QD) electrons via an adjacent tunneling-coupled GaNAs quantum well acting as a spin filter. The extraordinary spin filtering effect in GaNAs is enabled by spin-dependent recombination via spin-polarized defects, i.e. grown-in Ga self-interstitials, which selectively deplete conduction electrons with an opposite spin orientation to that of the defect electron. In sharp contrast to the general trend of deteriorating spin polarization with increasing temperature seen in all other approaches of spin generation, our approach is gifted with an opposite temperature dependence up to RT thanks to a thermally accelerated remote spin-filtering effect as a result of thermally activated recombination via the defects [2]. We further show that the QD electron spin can be remotely manipulated by spin control in the adjacent spin filter, paving the way for remote spin encoding and writing of quantum memory as well as for remote spin control of spin-photon interfaces. This work demonstrates the feasibility to implement opto-spintronic functionality under practical device operation conditions in a semiconductor nanostructure system based on the mature III-V semiconductor technology commonly used for today’s optoelectronics and photonics. It could also pave the way for a range of potential spintronic and opto-spintronic applications exploiting the state-of-the-art GaAs technology platform, such as spin-LEDs, spin lasers, spin-polarized single-photon sources, quantum spin-photon interfaces, spin qubits, etc.

Probing Spin-Dependent Ballistic Charge Transport at Single-Nanometer Length Scales.

The coherent transport of charge and spin is a key requirement of future devices for quantum computing and communication. Scattering at defects or impurities may significantly reduce the coherence of quantum-mechanical states, thereby affecting the device functionality. While numerous methods exist to experimentally assess charge transport, the real-space detection of a material's ballistic spin transport properties with nanometer resolution remains a challenge. Here we report on a novel approach that utilizes a combination of spin-polarized scanning tunneling microscopy (SP-STM) and the recently introduced molecular nanoprobe (MONA) technique. It relies on the local injection of spin-polarized charge carriers from a magnetic STM tip and their detection by a single surface-deposited phthalocyanine molecule via reversible electron-induced tautomerization events. Based on the particular electronic structure of the Rashba alloy BiAg2, which is governed by a spin-momentum-locked surface state, we prove that the current direction inverses upon tip magnetization reversal.

Spin-polarization and crystal structure engineering enhanced photocatalytic H2 production and photoluminescence properties in cobalt-doped CsPbBr3

In this study, the effect of Co doping in CsPbBr3 perovskite on phase transition and photocatalytic hydrogen production under a magnetic field was studied. Square CsPbBr3 nanoparticles with a dimension of 30–40 nm have been synthesized by the hot injection method. Rietveld refinement on the XRD pattern revealed the phase transition from cubic to orthorhombic after Co doping. The addition of 3%Co to CsPbBr3 resulted in a significant hydrogen production capacity of 3500 μmol/g in 4 h, with the maximum hydrogen production rate of 1042.11 μmol/g·h in the first hour, which was 1.80 times the maximum hydrogen production rate of bare CsPbBr3 (581.66 μmol/g·h). Notably, the photocatalytic H2 production of 3%Co: CsPbBr3 perovskite is significantly enhanced by applying an external magnetic field. Under the magnetic field of 2 T, the hydrogen production capacity of Co: CsPbBr3 increased to 5300 μmol/g in 4 h, with the maximum hydrogen production rate of 1828.36 μmol/g·h in the first hour, being 3.14 times the maximum hydrogen production rate of CsPbBr3 without magnetic field. The corresponding mechanism is systematically investigated by a vibrating-sample magnetometer, Electron paramagnetic resonance, UV–visible absorption, and photoluminescence spectra. The photocurrent and EIS were applied to investigate the charge-transfer kinetics of Co–CsPbBr3. The excellent photocatalytic H2 production efficiencies are because the doping of magnetic Co into highly polarized orthorhombic CsPbBr3 increased the number of spin-polarized photo-generated carriers while applying magnetic field provided spin polarization and more electron transport channels, suppressing the recombination efficiency of electrons and holes. Manipulating spin-polarized electrons in highly polarized orthorhombic photocatalytic semiconductors provides an effective strategy to boost photocatalytic H2 production efficiencies.

Gate voltage-controlled spin-rectifier diode based on Janus transition metal nitride MXene with spin gapless semiconductor

With the continuous application of spintronics technology, spintronic devices have been expected to become a major direction in the development of next-generation electronic devices. However, for spin rectifier diodes, how to provide a large number of spin-polarized carriers is still a key technical issue. Conventional spin-polarization injection models use ferromagnetic (FM)/semiconductor structures, but because of the conductivity mismatch can limit the injection of their polarization. This makes the search for spin-gapless semiconductor which has the conductivity between metals and semiconductors an effective way to solve this problem. Recently, MXene, a new two-dimensional material with high spin polarization, has been expected to undergo modulation of the electronic structure through external field or proximity effects. Subsequently, we propose a Janus transition metal structure of the MXene which modulates the spin properties by breaking the symmetry of the transition metals. Moreover, we find the band structure of TiCrNO2 can be effectively modulated by an applied electric field, which transforms itself from a magnetic semiconductor to a spin-gapless semiconductor under an electric field strength of 1 V/Å. With this as a basis, we construct a tunable spin rectifier diode and study its spin rectification effect by the first-principle calculations combined with non-equilibrium Green's function. The results show that the rectification ratio of the spin rectification diode can be adjustable by varying the strength of the external electric field, and its rectification rate exceeds the highest value currently available for two-dimensional rectifier devices. Our results provide a reference value for the application of nitride MXene in spintronic devices.