共查询到20条相似文献,搜索用时 62 毫秒
1.
在Brueckner-Hartree-Fock理论框架内,研究了自旋极化核物质的状态方程及其自旋依赖性,计算了相关的物理量如朗道参数G0和G′0,并着重讨论了三体核力的影响.结果表明:在整个自旋极化度范围内,自旋极化核物质的每核子能量随中子和质子自旋极化度的变化相当精确地满足二次方规律,而且在Brueckner-Hartree-Fock理论框架内,自旋非极化核物质的能量总是比相应的自旋极化核物质的能量低,这表明核物质中不会发生由自旋非极化态向自旋极化态的自发相变.当密度较低时,三体核力对核物质状态方程的自旋依赖性的影响不明显;随着密度的增大,三体核力效应增强,而且三体核力使朗道参数G0和G′0增大,从而使核物质对于自旋涨落的稳定性增强 相似文献
2.
在分子自旋电子学中,向非磁性的分子器件中注入自旋引起了广泛关注.在此提出一个新颖的策略,将磁性引入到与两个扶手椅形石墨烯纳米带电极耦合的单个苯分子器件中,即将这两个扶手椅形石墨烯纳米带电极的末端切割成锯齿形边缘的三角形石墨烯.利用第一性原理方法研究了分子结的自旋相关输运性质.结果表明,由于锯齿形边缘的三角形石墨烯向扶手椅形石墨烯纳米带电极和苯分子的自旋转移,导致锯齿形边缘三角形石墨烯的本征磁性减弱.有趣的是,虽然锯齿形边缘三角形石墨烯的本征磁性衰减了,但仍对分子结的自旋输运有显著的贡献.输运计算表明,在自旋平行构型下,可以获得较大的电流自旋极化率.然而,在自旋反平行构型下,电流的自旋极化率发生了反转.器件隧穿磁电阻的正负可以通过偏压来调控.这项工作提出了一个在新型分子自旋电子器件中设计和应用石墨烯纳米带的有趣方法. 相似文献
3.
采用量子化学方法设计并研究了一系列CH2、NH、O和Se取代的2,1,3-苯并噻二唑衍生物的电子性质、光谱性质和电荷传输性质.采用的研究方法是从头算Hartree-Fock和密度泛函方法.研究结果表明,中心芳环的S原子分别被CH2、NH、O和Se取代后,母体分子的电子性质、光谱性质以及电荷传输性质得到了很好的调节.根据得到的理论研究结果,在2,1,3-苯并噻二唑衍生物基础上进行结构修饰得到的一系列分子可以作为有机发光二极管中的有机发光材料. 相似文献
4.
用玻色化技术和高斯波泛函变分理论研究了电荷转移型Hubbard模型.通过自旋密度波和电荷密度波的位相结构的变化,并结合其相应能隙的变化,得到以下结论:系统的Ising相变与Mott相变不重合,中间有一个SDI(spontaneouslydimerizedinsulating)的过渡相.在BI(band-insulator)相,自旋密度波与电荷密度波都具有能隙,而在MI(Mott-insulator)相,电荷密度波具有能隙,自旋密度波没有能隙.
关键词:
Hubbard模型
电荷密度波
自旋密度波
相图 相似文献
5.
6.
在Brueckner–Hartree–Fock理论框架内,研究了自旋极化的中子物质的状态方程及其自旋依赖性,计算了自旋非对称能及相关的物理量如磁化率和朗道参数G0,并着重讨论了三体核力的影响,结果表明:在整个自旋极化度范围内,中子物质的每核子能量随自旋极化度的变化都满足二次方规律,自旋对称能随密度单调增加,这意味着中子物质中不会发生由自旋非极化态向自旋极化态的自发相变,三体核力的主要效应是使中子物质磁化率随密度减小的速度加快,从而使中子物质的磁化相变更加困难. 相似文献
7.
8.
9.
10.
根据存在自旋轨道耦合时基于散射理论的电流表达式和散粒噪声表达式,并利用自旋密度矩阵推导出沿自旋量子化坐标的自旋极化率表达式.解析计算了单通道的情况,发现自旋极化率和电荷流散粒噪声无关.由于多通道解析推导的困难,使用非平衡格林函数技巧,数值计算了包含自旋轨道耦合效应的纯净二维电子气的多通道情况.分别改变偏压、自旋轨道耦合系数、导体长度,研究了这三种不同条件下的自旋极化率与电荷流散粒噪声Fano因子的相关性.两者的相关性表明,相关性定量关系的建立可能为自旋极化的全电学检测提供新思路.
关键词:
散粒噪声
自旋极化
Rashba自旋轨道耦合
散射矩阵 相似文献
11.
A multi-conjugate adaptive optics (MCAO) can offer a possibility of widening field of view (FOV) characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle's expressions of two deformable mirrors (DMs) MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance. 相似文献
12.
Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use. 相似文献
13.
14.
A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
15.
40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
16.
Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
17.
Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
18.
Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
19.
The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
20.
References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献