自旋轨道耦合引起的电偶极矩

文章介绍了由于自旋轨道耦合导致的电子的电偶极矩在自旋电子学理论中的基本意义.研究发现,该电偶极矩与自旋流张量的反对称部分直接相关.它不仅直接导致可观测的电磁学效应,而且与电子在电场受到的力以及力矩有关,从而为自旋的电子学操控提供了可能.     

Polarization of Two Identical Atoms in an Electric Field

The polarization of two atoms which are in a linearly polarized monochromatic field and in a field of optical pulses is calculated. The problem is solved for the 2s→3p transitions taking into account the initial states of the atoms. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 57–59, July, 2005.     

Apparently Negative Electric Polarization in Shaped Graded Dielectric Materials

By using a first-principles approach, we investigate the pathway of electric displacement fields in shaped graded dielectric materials existing in the form of cloaks with various shapes. We reveal a type of apparently negative electric polarization （ANEP）, which is due to a symmetric oscillation of the paired electric permittivities, satisfying a sum rule. The ANEP does not occur for a spherical cloak, but appears up to maximum as a/b （the ratio between the long and short principal axis of the spheroidal cloak） is about 5/2, and eventually disappears as a/b becomes large enough corresponding to a rod-like shape. Further, the cloaking efficiency is calculated for different geometrical shapes and demonstrated to closely relate to the ANEP. The possibility of experiments is discussed. This work has relevance to dielectric shielding based on shaped graded dielectric materials.     

Electric Polarization in ErCrO3 Induced by Restricted Polar Domains

Physics of the Solid State - Electric polarization in ErCrO3 single crystals has been investigated in the temperature range of 5‒370 K. Ferroelectric ordering has not been found in any of the...     

Plasma Polarization Around Dust Particle in an External Electric Field

The effect of plasma polarization around a negatively charged dust particle is investigated with the help of Monte Carlo simulation of ion trajectories in the electric field of the dust particle and an external electric field. The induced dipole moment of such a system was estimated in a wide range of dust particle and plasma parameters. It is shown that the dipole moment is very large, and has a non‐monotonous dependence on the external electric field. For a small external electric field, it weakly depends on the charge of the dust particle. The dipole moment reduces with the decrease of ion mean free path (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

AlGaN合金中局域态和极化电场的竞争机制

通过MOVPE方法生长了不同Al组分的3块Al_xGa_1-xN样品,利用稳态光谱和时间分辨光谱对其样品的光学特性进行了分析。鉴于影响氮化物发光性质的极化电场或局域态的单一机制不能充分解释我们的实验现象,提出了局域态-内部极化电场竞争的机制。通过对实验数据的分析,得出如下重要结论：样品PL峰位蓝移的温度起点基本对应于局域态和极化电场起作用的交替点,PL峰位发生蓝移的温度起点与光强-温度曲线的斜率出现明显变化的温度点一致;随着温度的升高,若AlGaN合金样品中PL峰位存在二次蓝移,则说明样品中电场分布不均匀。     

Magnetic-Field-Induced Semimetal-Insulator-like Transition in Highly Oriented Pyrolitic Graphite

We report the extraordinarily large positive magnetoresistances （MR, 69400% at 4.5K under a magnetic field of 8.15 T）, de Hass-van Alphen oscillations effect at 10 K and the semimetal-Jnsulator-like transition in a wide range of temperature in highly oriented pyrolitic graphite （HOPG）. Besides a dominating ordinary MR （OMR） mechanism in the free-electron mode, it is realized from qualitative analysis that the Coulomb interacting quasiparticles within graphite layers play some roles. However it is difficult to associate the transition with the simple OMR theory. In order to investigate the possible origins of the transition, further analysis is carried out. It is revealed that the magnetic-field-induced behaviour is responsible for the semimetal-insulator-like transitions in HOPG.     

Magnetic-Field-Induced Strains of Bonded Ni-Mn-Ga Melt-Spun Ribbons

Non-stoichiometric Ni50Mn27 Ga23 polycrystalline ribbons are prepared by melt-spinning technique. The magneticfield-induced strain （MFIS） of Ni-Mn-Ga bulk alloy prepared by bonding the melt-spun ribbons is obtained. The experimental results show that Ni50Mn27Ga23 bonded ribbons exhibit a typical thermal-elastic shape memory effect in the thickness direction. The martensitic transformation strain of bonded ribbons is an expansive strain of about 0.3% without the magnetic field and a contractive strain of about -0.46% at the magnetic field of 1 T. The field can not only enhance the value of the martensitic transformation strain of the bonded ribbons, but can also change the direction of the strain. The bonded ribbons alloy presents negative MFIS and obtains a larger value of the strain though influenced by the adhesive between the ribbons. Therefore, the preparation technique of the Ni-Mn-Ga bulk alloy by bonding melt-spun ribbons is helpful to get rid of the size restriction of the ribbon and to broaden the applications of the ribbons.     

Observation of Sub-femtosecond Polarization Beats Using Twin Noisy Driving Fields

We study the phase-conjugate polarization interference in a V-type three-level system and obtain an analytic closed form for the second-order stochastic correlation of sum-frequency polarization beat. In our Na vapour atomic system pumped by laser pulse of nano-second timescale duration, we experimentally demonstrate an ultrafast modulation of the four-wave mixing signal intensity with a sub-femtosecond timescale period, corre- sponding to the sum-frequency of the resonant transitions from 3S1/2 to 3Pl/2 and 3P3/2.     

正铁氧体SmFeO_3高压拉曼研究(英文)

本文主要通过高压拉曼光谱研究了正铁氧体SmFeO3的晶格振动模式在外加压力作用下的行为规律,高压实验中压力最高为29.7GPa。本文采用溶胶凝胶法,制备出具有正交结构,其空间群为Pnma的SmFeO3。在外加压力作用下,所有观察到的拉曼振动模式都呈现出宽化趋势。特别是位于621.1cm-1的FeO6八面体的反弹性振动模式Ag(1)与位于452.7cm-1的FeO6八面体的弯曲振动模式B3g(3),其压力系数出现最大值。与此相反,Sm-O振动模式Ag(7)的压力系数却非常小。这说明外加压力更容易影响到FeO6八面体的晶格变化,而不是SmO12十七面体的改变。SmFeO3的这种高压下晶格振动模式变化行为类似于G型结构的CaSnO3。同时,文中还给出了所有声子零压模式下的格林爱森参数与体弹模量的比值。这些参数可用于进一步测量单轴或者双轴的应变力,可深入理解声子频率在张力作用下移动的表现行为。     

卫星遥感中不同偏振量对气溶胶反演的影响分析

偏振探测是提高气溶胶卫星遥感能力的重要途径.作为目前全球重要的偏振数据源,我国高分五号卫星搭载的多角度偏振探测仪(DPC)能够测量不同的偏振量,包括Stokes矢量偏振分量、偏振辐亮度(Lp)和线偏振度(DOLP).各偏振量所包含的有效信息和测量误差不同,进而影响气溶胶参数的反演精度.针对此,在最优估计反演框架下,利用...     

稀土发光配合物和高分子PVK之间的能量传递及其在高分子中的分散状态研究

我们使用乙酰水杨酸（aspirin)作为第一配体、邻菲罗琳（phen)为第二配体,在乙醇溶液中合成了稀土发光配合物。元素分析和红外光谱证明它的分子组成的TbC27N2O12H28、分子式就为Tb(aspirin)3phen。光致发光研究表明导电高分子（PVK）和稀土配合物之间存在Foerster能量传递现象。这种能量传递的一个必要条件应该是稀土配合物的激发谱和高分子PVK的发射谱有重叠。稀土配合物掺杂高分子PVK的透射电镜照片表明稀土配合物在高分子PVK中分散比较均匀,分散尺度在20-30nm之间。同时,我们发现高分子PVK和稀土配合物混合后不能均匀分散,这可能是影响电致发光器件寿命的一个因素。     

Effect of Electric Current on the Spin Polarization of Electrons in Materials with Nonuniform Magnetization

Journal of Experimental and Theoretical Physics - The nonequilibrium magnetization (spin polarization) of conducting electrons moving in materials with a nonuniform magnetization distribution is...     

Electric Polarization in YCrO3 Induced by Restricted Polar Domains of Magnetic and Structural Natures

Physics of the Solid State - The electric polarization induced by local polar domains of two types (phase separation domains of magnetic nature and structure-distorted domains) has been observed in...     

正交偏振多光谱成像术应用于活体微循环观察研究

构建一种小型、简洁的活体微循环多光谱成像系统,将正交偏振光谱成像术OPS Imaging及液晶可调谐滤光片LCTF应用于活体微循环多光谱成像。LCTF具有较高的成像质量、较低的功耗、且没有移动部件和图像移动,能够连续、随机地在可见-近红外波段上快速实现波长的任意调谐。利用该系统,对活体裸鼠的耳廓采用检偏角为90°(正交偏振方式)与0°两种方式进行了试验,获取了裸鼠耳廓微血管的多光谱图,得出采用正交偏振成像方式的图像的对比度及图像细节均优于检偏角为0°时的图像。试验验证了正交偏振多光谱成像技术能增强活体微循环观察效果。     

Electric Polarization of Inhomogeneously Strained Rare-Earth Crystals with a Garnet Structure and Related Films

Physics of the Solid State - The influence of inhomogeneous strains on the occurrence of electric polarization of rare-earth compounds with a garnet structure has been analyzed. Polarization of the...     

自旋轨道耦合和电势共同调节的石墨烯中的自旋极化性质

近年来,石墨烯中电子的自旋相关输运引起了越来越多的关注.本论文应用转移矩阵的方法讨论了石墨烯中具有单个界面或者两个界面的结构中,受到自旋-轨道耦合作用和电势的共同影响下自旋相关的输运性质.对于单个界面结构,由于自旋-轨道耦合作用导致能级产生劈裂,在固定的入射能量下,电子在自旋-轨道耦合区域产生两种传播模式.在自旋-轨道耦合区域加了电势后,透射几率和模式临界角都会受到较大的影响.对于两个界面结构,粒子的透射几率不仅与入射角有关,还与自旋-轨道耦合区域的宽度和自旋进动长度有关,而电势对同自旋方向的传输几率以及自旋反转的几率都有影响,适当地选取系统的参数和电势的大小,可以控制出射的电子自旋方向,实验上可以用来设计自旋反转器或者或者自旋控制器.     

Dispersion of Exciton Polaritons in Terbium Nitrate Hexahydrate

The dispersion relations of exciton polariton waves in terbium nitrate hexahydrate are determined based on the model of the interaction of electromagnetic waves with resonant electronic states of Tb³⁺ ions at the ⁵D₄–⁷F₆ transition. Frequencies of unitary polaritons characterized by refractive indices equal to unity are determined. It is shown that the group velocity of electromagnetic waves in the region of unitary polaritons is lower than the speed of light in vacuum by several orders of magnitude. A sharp increase in the efficiency of photoluminescence and Raman scattering is predicted in the case where the excitation radiation frequency approaches the unitary polaritons frequency.