Spintronic terahertz emitter with integrated electromagnetic control

Spintronic thin films are considered as one of the promising terahertz(THz) source candidates, owing to their high performance and low cost. Much effort has been made to achieve spintronic THz sources with broadband and high conversion efficiency. However, the development of spintronic THz emitters with good compatibility, low cost, and miniaturized technology still faces many challenges. Therefore, it is urgent to extend commercial and portable spintronic THz emitters to satisfy many practical ...     

Spintronic devices for neuromorphic computing

正In the past decades, significant progress has been achieved in artificial intelligence, which is now widely applied in image recognition, big data analysis, unmanned vehicle control and other cognitive tasks [1]. These applications nevertheless are highly energy consuming partly because of the mismatch between the neural-network-computing-based software implementation and the von Neumann architecture of present computers. One promising solution is developing neuro-     

Spintronic devices as quantum networks

We explore spintronics from a quantum information (QI) perspective. We show that QI specific methods can be an effective tool in designing new devices. Using the formalism of quantum gates acting on spin and mode degrees of freedom, we provide a solution to a reverse engineering problem, namely, how to design a device performing a given transformation between input and output. Among these, we describe an orientable Stern-Gerlach device and a new scheme to entangle two spins by transferring the entanglement from orbital to spin degrees of freedom. Finally, we propose a simple scheme to produce hyperentangled electrons, i.e., particles entangled in both the spin and mode degrees of freedom.     

自旋电子学材料、物理和器件设计原理的研究进展

文章介绍了作者所在实验室在巨磁电阻(GMR)、隧穿磁电阻(TMR)、庞磁电阻(CMR)和反铁磁钉扎薄膜材料以及单晶金属氧化物、高自旋极化率材料、P-N异质结和纳米环磁随机存储器原理型演示器件设计等研究方面取得的一些重要研究成果和进展.例如:在Al-O势垒磁性隧道结材料体系里,获得室温磁电阻超过80%的国际最好结果;获得两种高性能层状反铁磁钉扎材料体系;发现具有大的电致电阻效应的CMR薄膜材料,并可期望用于电流直接进行磁信息写和读操作的磁存储介质;发现双势垒磁性隧道结中的量子阱态共振隧穿和磁电阻振荡效应,以及纳米器件体系中自旋翻转长度的观测新方法,可用于新型自旋电子学材料及相关器件的人工辅助设计;利用电子自旋共振谱探测和研究了金属氧化物的微观自旋结构和各向异性;在[CoFe/Pt]n磁性金属多层膜中,观测到超高灵敏度的反常霍尔效应;利用纳米环状磁性隧道结作为存储单元,研制出一种新型纳米环磁随机存储器MRAM原理型演示器件.     

Cobalt-Dioxolene Redox Isomers: Potential Spintronic Devices

Cobalt-dioxolene complexes may show redox isomerism (valence tautomerism). This phenomenon is due to intramolecular electron transfer within the cobalt(III)-catecholato moiety yielding a cobalt(II)-semiquinonato species. The relative stability of the two redox isomers is determined by temperature and it is possible to stimulate the interconversion from the stable isomer to the metastable one upon irradiation at appropriate wavelengths. Since the energies of the two isomers are different, irradiation is followed by a decay process to the ground state. Theory predicts that dynamics of relaxation should be basically controlled by the energy gap between the two interconverting isomers. A series of cobalt complexes of general formula [Co(Me _n tpa)(diox)]PF·solv(diox = 3,5-di-tert-butyl-1,2-dioxolene, solv = ethanol, toluene) has been prepared using as an ancillary ligand the tripod-like Me _n tpa (n = 0, 1, 2, 3), derived by tris(2-pyridylmethyl)amine (tpa) by successive introduction of methyl groups into 6-position of pyridine moieties. The steric hindrance induced by this substitution modulates the redox properties of the metal acceptor, thus determining the charge distribution of the metal-dioxolene moiety at room temperature. Optically induced redox isomerism was observed by irradiating at cryogenic temperatures the Co(Me _n tpa)(diox)PF complexes (n = 0, 1, 2). The different kinetics of relaxation of the photo-induced metastable phases are related to the respective free energy changes of the interconversion, as estimated by cyclic voltammetry experiments at room temperature, and to the different lattice interactions, as supported by structural data. These results show the importance of molecular techniques in the perspective of controlling the relaxation properties of photo-induced metastable species.     

自旋电子学材料、物理和器件设计原理的研究进展

文章介绍了作者所在实验室在巨磁电阻(GMR)、隧穿磁电阻(TMR)、庞磁电阻(CMR)和反铁磁钉扎薄膜材料以及单晶金属氧化物、高自旋极化率材料、P-N异质结和纳米环磁随机存储器原理型演示器件设计等研究方面取得的一些重要研究成果和进展.例如：在Al-O势垒磁性隧道结材料体系里,获得室温磁电阻超过80%的国际最好结果;获得两种高性能层状反铁磁钉扎材料体系;发现具有大的电致电阻效应的CMR薄膜材料,并可期望用于电流直接进行磁信息写和读操作的磁存储介质;发现双势垒磁性隧道结中的量子阱态共振隧穿和磁电阻振荡效应,以及纳米器件体系中自旋翻转长度的观测新方法,可用于新型自旋电子学材料及相关器件的人工辅助设计;利用电子自旋共振谱探测和研究了金属氧化物的微观自旋结构和各向异性;在［CoFe/Pt］n磁性金属多层膜中,观测到超高灵敏度的反常霍尔效应;利用纳米环状磁性隧道结作为存储单元,研制出一种新型纳米环磁随机存储器MRAM原理型演示器件.     

Voltage-Driven Adaptive Spintronic Neuron for Energy-Efficient Neuromorphic Computing

A spintronics neuron device based on voltage-induced strain is proposed.The stochastic switching behavior,which can mimic the firing behavior of neurons,is obtained by using two voltage signals to control the in-plane magnetization of a free layer of magneto-tunneling junction.One voltage signal is used as the input,and the other voltage signal can be used to tune the activation function(Sigmoid-like) of spin neurons.Therefore,this voltage-driven tunable spin neuron does not necessarily use ener...     

与半导体相容的半金属铁磁体

文章在自旋电子学与新型计算机元件的背景下介绍了与半导体相容的半金属铁磁体，及其实验和理论研究进展情况．指出其中半稳能量低并且稳定性好的理论预测材料有可能不久通过外延方式在合适的基底上生长出来，并且得到实际应用．     

Photoelectrolysis of water with semiconductors

The use of semiconductors, as photoelectrodes in electrolytic cells for the electrolysis of water, is described and the results reported in the literature for various semiconductors are reviewed. The most important properties of the semiconductor are shown to be the band-gap energyE _g , and the flat-band potentialU _fb . The semiconductor absorbs photons that are more energetic than the band-gap energy and creates electronhole pairs. These charge carriers can be separated before recombination by the electric field at the semiconductor-electrolyte interface. For electrolysis to proceed, the potential corresponding to the band gap must appreciably exceed the standard potential for the electrolysis of water, 1.23 volts. In addition, the flat-band potential must be more negative than the hydrogen potential or an external bias voltage is required. The semiconductor must not corrode under the operating conditions and must permit transfer of the minority carrier to the electrolyte. The current theories of charge transfer and reaction mechanism are discussed. Many semiconductive oxides have been tested as photoanodes and found to be stable. However, only those compounds that have band gaps of ca. 3 eV have been found to have flat-band potentials that are more negative than the hydrogen potential. These compounds will electrolyse water, without additional bias voltage, but are inefficient absorbers of solar energy. Experiments withp-type photocathodes,p andn combinations and various special configurations are also described. The paper concludes with a general discussion of the practical prospects of photoelectrolysis in comparison with solid-state solar cells.     

n-p共掺杂材料体系自旋电子学性质研究进展

掺杂在调控材料体系的物理化学性质方面起着重要的作用.n-p共掺杂方法借助n型和p型掺杂物间强的静电相互作用,能够解决一些材料体系研究中存在的关键性问题,进而有效的改进这些体系的某方面特殊性质.本文中,将首先介绍n-p共掺杂方法;然后,分别从非补偿性n-p共掺杂和补偿性n-p共掺杂出发,对近些年来,明确利用n-p共掺杂方法,在稀磁半导体、石墨烯以及拓扑绝缘体等不同材料体系自旋电子学性质的相关研究进行详细介绍,并对n-p共掺杂方法在未来研究中的可能应用进行展望.     

Exchange coupling in multilayers with semiconductors

Intrinsic and heat-induced exchange coupling exists between ferromagnetic films separated by non-magnetic semiconducting spacer layers. Magnetic coupling across thin amorphous layers of Si, SiO, Ge and Ge/Si heterostructures is described. Antiferromagnetic coupling occurs in a limited thickness range for Si and Si/Ge heterostructures, and ferromagnetic coupling is found for SiO, Ge, and certain thicknesses of Si and Si/Ge heterostructures. The coupling strength is very weak, of the order of a few 10^–6 J/m². It exhibits a pronounced temperature dependence with a positive temperature coefficient for both ferro- and antiferromagnetic couplings. The observations indicate that resonant tunneling through defect states in the spacer material mediates the exchange coupling.     

Stanene: A Promising Material for New Electronic and Spintronic Applications

The attractive mechanical and electronic properties of freestanding graphene has led to the exploration of two‐dimensional (2D) materials which can be integrated with contemporary electronics. As a 2D analog of graphene, stanene has become a hopeful candidate for 2D films due to its excellent quantum effects, superconductivity, and thermoelectric properties. Focusing on the promising 2D elemental material stanene, the fundamental electronic properties and experimental preparation of this material are reviewed. The prospects of utilizing the ability to manipulate the electronic properties of stanene for nanoelectronic and optoelectronic applications are determined.     

Auger recombination with traps in quantum-well semiconductors

Auger recombination involving traps is calculated for quantum-well semiconductors. Apart from some modifications the results are analogous to those for bulk semiconductors. In particular, the lifetime of the recombination process is proportional to the inverse carrier density and independent of temperature.     

Silicon MOS structures with nonstoichiometric metal-oxide semiconductors

MOS structures are formed by oxidative annealing of tin, tungsten, palladium, nickel, and zinc thin films on silicon, and their high-frequency C-V characteristics are measured. The energy spectra of the density of surface states taken of SnO_{2 ? x} , WO_{3 ? x} and PdO_x nonstoichiometric oxides are found to have common features.     

Auxiliary-level-assisted operations with charge qubits in semiconductors

We present a new scheme for rotations of a charge qubit associated with a singly ionized pair of donor atoms in a semiconductor host. The logical states of such a qubit proposed recently by Hollenberg et al. [16] are defined by the lowest two energy states of the remaining valence electron localized around one or another donor. We show that an electron located initially at one donor site can be transferred to another donor site via an auxiliary molecular level formed upon the hybridization of the excited states of two donors. The electron transfer is driven by a single resonant microwave pulse in the case where the energies of the lowest donor states coincide or by two resonant pulses in the case where they differ from each other. Depending on the pulse parameters, various one-qubit operations—including the phase gate, the NOT gate, and the Hadamard gate—can be realized in short times. Decoherence of an electron due to the interaction with acoustic phonons is analyzed and shown to be weak enough for coherent qubit manipulation to be possible, at least in proof-of-principle experiments on one-qubit devices.     

Crystallization of chalcogenide glassy semiconductors with admixtures

Crystallization of chalcogenide glassy semiconductors with different contents of admixtures were investigated. It was shown that photoluminescence studies can reveal a lack of the centers responsible for radiation, i.e., possessing negative correlation energy, and the onset of crystallization in chalcogenide glassy semiconductors.