自旋电子学研究的最新进展

自旋极化电子的高效注入、自旋霍尔效应和自旋流的产生与探测都是目前自旋电子学中热门研究专题,世界一些著名学术刊物屡见报道。对这些重要内容的理论和实验的最新研究成果进行了介绍。通过自旋极化电子高效注入方法和材料的研究,人们期望研制出新一代自旋电子器件,进而实现应用电子自旋传输、记录和存储信息的目标。近期实验给出,自旋极化电子从铁磁金属注入半导体和金属都获得较高的极化率。各种注入方法中,自旋流直接注入法目前备受关注,因为自旋霍尔效应为自旋流的产生与探测提供了新的途径,即自旋霍尔效应可以产生自旋流,但因无霍尔电压故不容易测量;而逆自旋霍尔效应又将自旋流转化为电流,使得难以测量的自旋流又可以直接用电学方法测量。     

自旋电子学研究进展

自旋电子学是上世纪 90年代以来飞速发展起来的新兴学科。与传统的半导体电子器件相比 ,自旋电子器件具有非挥发性、低功耗和高集成度等优点。电子学、光学和磁学的融合发展更有望产生出自旋场效应晶体管、自旋发光二极管、自旋共振隧道器件、THz频率光学开关、调制器、编码器、解码器及用于量子计算、量子通信等装置的新型器件 ,从而触发一场信息技术革命。文中介绍了自旋电子学的若干最新研究进展。     

惰性气体核的自旋交换光抽运中的物理

核自旋极化的惰性气体原子在诸如核物理、材料科学和磁共振成像等许多领域中都有着广泛的应用,核自旋极化技术涉及领域很广,包括原子、分子和光学物理等等。评述了光抽运和自旋交换碰撞中角动量转移和损失的物理。     

SiGe/Ge/SiGe异质结构中自旋极化输运特性的模拟

利用蒙特卡罗方法对SiGe/Ge/SiGe异质结构的自旋极化输运特性进行了模拟研究.在Ge沟道调制掺杂异质结构形成的二维空穴气中,空穴的自旋进动主要受Rashba自旋轨道相互作用控制.在77～300K的温度范围内,对自旋散射长度、自旋极化率等自旋极化输运特性进行了研究.模拟结果显示,低温和窄宽度沟道有利于减小散射对自旋极化输运的影响,避免自旋极化率衰减,增大自旋散射长度.栅控的漏端电流自旋相关效应使器件跨导增大,并产生负跨导效应.     

SiGe/Ge/SiGe异质结构中自旋极化输运特性的模拟

利用蒙特卡罗方法对SiGe/Ge/SiGe异质结构的自旋极化输运特性进行了模拟研究．在Ge沟道调制掺杂异质结构形成的二维空穴气中,空穴的自旋进动主要受Rashba自旋轨道相互作用控制．在77～300K的温度范围内,对自旋散射长度、自旋极化率等自旋极化输运特性进行了研究．模拟结果显示,低温和窄宽度沟道有利于减小散射对自旋极化输运的影响,避免自旋极化率衰减,增大自旋散射长度．栅控的漏端电流自旋相关效应使器件跨导增大,并产生负跨导效应．     

自旋晶体管的最新研究进展

自旋晶体管是指利用电子自旋自由度构建的在结构上类似于传统半导体晶体管的三端自旋器件。对基于自旋劈裂的磁双极型自旋晶体管、基于热电子输运的自旋晶体管和基于Rashba效应的自旋晶体管的最新研究动态进行了评述,并对其发展前景做了展望。     

有机无机杂化钙钛矿半导体中光激发态自旋的光学探测

概述三维与二维钙钛矿材料(HOP)电子自旋光学响应的基本过程、电子态自旋寿命的光学测量方法和结果,并对已知自旋寿命的影响因素进行分析,讨论进一步研究钙钛矿在自旋阀、自旋输运、量子计算、偏振发光二极管等基于钙钛矿中自旋特性的应用中的前景。     

基于超快电子自旋动力学的太赫兹辐射研究进展

回顾了近年来利用超快自旋动力学过程产生太赫兹(THz)辐射的研究进展。介绍了基于逆自旋霍尔效应和逆Rashba-Edelstein效应的瞬态自旋流-电荷流转换,指出铁磁/非磁性异质结构已被用于设计低成本、高效率的THz辐射源。通过优化膜厚、生长条件、衬底和结构,可进一步提高基于自旋电子学的THz发射器的效率和带宽。简述了THz发射光谱在研究超快自旋泽贝克效应形成动力学中的应用。     

光的自旋-轨道相互作用北大核心CSCD

光的自旋-轨道相互作用是指光的自旋角动量和轨道角动量之间的相互作用,它存在于反射、折射、散射、衍射、聚焦等基本的光学过程中。在传统大尺度量级的经典光学中可以忽略自旋-轨道相互作用的影响,但在亚波长尺度下,自旋和轨道角动量之间会发生强耦合。对光的自旋-轨道相互作用的基本起源和重要应用进行了综述。首先,介绍了光的自旋-轨道相互作用的两个重要基本概念:光子角动量和几何相位理论。其次,分别介绍了自旋-内禀轨道角动量和自旋-外禀轨道角动量两种相互作用的基本原理。然后,重点介绍了光自旋-轨道相互作用的研究进展以及代表性应用。最后,对光自旋-轨道相互作用相关研究面临的挑战和未来的研究方向进行了展望。     

纳米尺寸自旋阀中电流驱动的自旋波发射

提出了在纳米赝自旋阀中的电流感应自旋传输矩的磁动力学描述,成功地解释了在磁纳米多层结构中的电流驱动微波发射和电流感应磁化翻转现象。自旋流极化由在电导匹配时的自旋流和化学势连续性边界条件决定。自旋矩的纵向和横向分量在自旋阀的电流驱动微波发射和电流感应磁化翻转现象中扮演了不同的角色:纵向自旋矩分量决定了电流感应磁化翻转(CIMS)效应,而横向自旋矩是自旋波发射(SWE)效应所不可缺少的。根据这一理论,由LLG方程自然得到自旋波发射的双模,分别为横向自旋矩引发的X和Y方向的振动,并引起磁多层电阻以频率2w或w(进动频率)随时间变化。磁场和自旋流共同决定了自旋波发射的频率和功率,这一理论预言了某种特殊的磁多层结构,如磁层相互垂直的结构,将具有大得多的微波发射效率,这一结论已经被实验所证实。     

基于自旋阀结构的磁传感器的研究

自旋阀结构的发现为磁电子学以及磁传感器的研究揭开了新的一页。基于自旋阀结构的磁传感器由于具有灵敏度高、功耗小、高集成度等优点,因此在传感器工业中具有广泛的应用前景。本文介绍了基于自旋阀结构的磁传感器的研究方法。首先介绍了自旋阀结构及其特性,然后介绍了基于自旋阀结构的磁性薄膜的制备方法和结构优化,其次介绍了基于自旋阀薄膜的磁传感器芯片的制造工艺,最后介绍了基于惠斯通电桥结构的自旋阀磁传感器芯片。     

自旋电子学和自旋电子器件

自旋电子学是近年来发展起来的微电子学和磁学的交叉学科,主要研究自旋极化电流的注入、控制和检测。本文介绍了自旋电子学和器件的研究进展,着重讨论了自旋注入和检测的问题,分析了自旋电子器件研究的核心问题和难点。自旋电子学的研究有着重要的理论意义,自旋器件在信息科学领域也具有十分广阔的应用前景。     

Concepts of Spin Seebeck Effect in Ferromagnetic Metals

Spin Seebeck effect (SSE) and related spin caloritronics have attracted great interest recently. However, the definition of the SSE coefficient remains to be established, let alone a clean experiment to measure the SSE coefficient in ferromagnetic metals. The concept through a model based on the semi‐classical Botlzmann transport equation has been clarified. The model includes the vital spin‐flip process, which is frequent in metals, and points out that the length scale of SSE is much larger than the spin diffusion length. The model reveals how the spin‐flip process influences the transport equations and provides the simple relationship between the different spin‐flip relaxation times for spin‐up and ‐down electrons, which is very useful to understand the spin transport properties. This understanding allows to redefine the expression of the spin Seebeck coefficient.     

Enhanced Spin Seebeck Effect in Monolayer Tungsten Diselenide Due to Strong Spin Current Injection at Interface

The spin current is significantly limited by the spin‐orbit interaction strength, material quality, and spin‐mixing conductance at material interfaces. Such limitations lead to spin current decay at the interfaces, which severely hinders potential applications in spin‐current‐generating thermoelectric devices. Thus, methodical studies on the enhancement of spin currents are indispensable. Herein, a novel approach for enhancing the spin current injected into a normal metal, Pt, using interface effects with a ferromagnetic insulator, yttrium iron garnet (YIG), is demonstrated. This is accomplished by inserting atomically thin monolayer (ML), tungsten diselenide (WSe₂) between Pt and YIG layers. A comparative study of longitudinal spin Seebeck effect (LSSE) measurements is conducted. Two types of ML WSe₂ (continuous and large‐area ML WSe₂ and isolated ML WSe₂ flakes) are used as intermediate layers on YIG film. Notably, the insertion of ML WSe₂ between the Pt and YIG layers significantly enhances the thermopower, V_LSSE/ΔT by a factor of approximately 5.6 compared with that of the Pt/YIG reference sample. This enhancement in the measured LSSE voltages in the Pt/ML WSe₂/YIG trilayer can be explained by the increased spin‐to‐charge conversion at the interface owing to the large spin‐orbit coupling and improved spin mixing conductance with the ML WSe₂ intermediate layer.     

Fe/GaAs中自旋注入效率的研究

自旋电子学是近年来发展迅速的一个研究领域,利用了传导电子自旋这一自由度的自旋电子器件以其提高数据处理速度、降低能量消耗、容易增加集成密度等优点正引起人们的空前关注.文中阐述了自旋的漂移-扩散方程,并对以Fe/GaAs为代表的铁磁性金属/半导体结构(FM/SC)进行了简单分析.如果选取参数适当,可以在Fe/GaAs结中获得较大的自旋注入效率.     

Spin‐Torque Manipulation for Hydrogen Sensing

External manipulation of spin‐orbit torques (SOTs) promises not only energy‐efficient spin‐orbitronic devices but also versatile applications of spin‐based technologies in diverse fields. However, the external electric‐field control, widely used in semiconductor spintronics, is known to be ineffective in conventional metallic spin‐orbitronic devices due to the very short screening length. Here, an alternative approach to control the SOTs by using gases is shown. It is demonstrated that the spin‐torque generation efficiency of a Pd/Ni₈₁Fe₁₉ bilayer can be reversibly manipulated by the absorption and desorption of H₂ gas, which appears concomitantly with the change of the electrical resistance. It is found that compared with the change of the Pd resistance induced by the H₂ absorption, the change of the spin‐torque generation efficiency is almost an order of magnitude larger. This result provides a new method to externally manipulate the SOTs and paves a way for developing more sensitive hydrogen sensors based on the spin‐orbitronic technology.     

Dirac Cone Spin Polarization of Graphene by Magnetic Insulator Proximity Effect Probed with Outermost Surface Spin Spectroscopy

The effects of the proximity contact with magnetic insulator on the spin‐dependent electronic structure of graphene are explored for the heterostructure of single‐layer graphene (SLG) and yttrium iron garnet Y₃Fe₅O₁₂ (YIG) by means of outermost surface spin spectroscopy using a spin‐polarized metastable He atom beam. In the SLG/YIG heterostructure, the Dirac cone electrons of graphene are found to be negatively spin polarized in parallel to the minority spins of YIG with a large polarization degree, without giving rise to significant changes in the π band structure. Theoretical calculations reveal the electrostatic interfacial interactions providing a strong physical adhesion and the indirect exchange interaction causing the spin polarization of SLG at the interface with YIG. The Hall device of the SLG/YIG heterostructure exhibits a nonlinear Hall resistance attributable to the anomalous Hall effect, implying the extrinsic spin–orbit interactions as another manifestation of the proximity effect.