共查询到20条相似文献,搜索用时 15 毫秒
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《Physica A》1995,220(3-4):585-598
An antiferromagnetic equivalent-neighbour Heisenberg interaction Hi between impurity spins is added to the reduced s-d Hamiltonian Hr previously introduced by simplifying the Kondo s-d exchange Hamiltonian HK. Asymptotic mean-field theory is developed for Hr + Hi, in the presence and absence of external magnetic field, and applied to (La1−xCex)Al2 alloys. Specific heat ci(T) and zero-field susceptibility χi(0,T) curves for (La1−xCex)Al2 are depicted. The coupling constants of Hr + Hi and conduction bandwidth are adjusted so that Tc temperatures for x = 0.2, 0.1 are equal to the experimental values. ci(T) exhibits a jump at Tc and is decreasing for T < Tc. χi(0,T) has a first order pole at Tc which corresponds to the maximum of experimental susceptibility and χi(0,0) > 0. These results improve those obtained earlier on the grounds of Hr theory. 相似文献
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研究了反向衬底偏压VB下纳米N沟道金属氧化物半导体场效应晶体管中栅调制界面产生(GMG)电流IGMG特性, 发现IGMG曲线的上升沿与下降沿随着|VB|的增大向右漂移. 基于实验和理论模型分析, 得出了VB与这种漂移之间的物理作用机制, 漂移现象的产生归因于衬底偏压VB 调节了表面电势φs在栅电压VG 中的占有比重: |VB|增大时相同VG下φs会变小, φs 的变化继而引发上升沿产生率因子gr减小以及下降沿产生率因子gf增大. 进一步发现IGMG 上升沿与下降沿的最大跨导GMR, GMF 在对数坐标系下与VB成线性关系, 并且随着|VB|增加而增大. 由于漏电压VD在IGMG 上升沿与下降沿中的作用不同, 三种VD下GMR-VB曲线重合而GMF-VB曲线则产生差异. 增大VD 会增强gf 随VG的变化, 因此使得给定VB 下的GMF变大. 同时这却导致了更大VD下GMF-VB 曲线变化的趋势减缓, 随着VD从0.2 V变为0.6 V, 曲线的斜率s从0.09减小到0.03.
关键词:
产生电流
表面势
衬底偏压
N沟道金属氧化物半导体场效应晶体管 相似文献
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We study the discrete Painlevé equations associated to the affine Weyl group which can be obtained by the implementation of a special limits of -associated equations. This study is motivated by the existence of two -associated discrete both having a double ternary dependence in their coefficients and which have not been related before. We show here that two equations correspond to two different limits of a -associated discrete Painlevé equation. Applying the same limiting procedures to other -associated equations we obtained several -related equations most of which have not been previously derived. 相似文献
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R. Jin H. R. Ott D. P. Grindatto 《Physica C: Superconductivity and its Applications》1995,250(3-4):395-402
The anisotropy of the normal-state resistivity of a number of superconducting Bi1.95Sr1.65La0.4CuO6+δ single crystals has been measured by using both a six- and a four-terminal technique. We find that the ab-plane resistivity ab in general increases almost linearly with temperature (dab/dT> 0). the temperature variation of the c-axis resistivity c, however, is strongly sample dependent. Both metallic-like (dc/dT> 0) and mixed temperature dependences of c, including dc/dT < 0 are observed. The mixed c(T) data can be well described by fitting to c(T) = A + BT + C/T, indicating that the temperature dependence of c(T) is the result of a competition between metallic and non-metallic terms. The temperature Tmin at which c reaches a minimum increases with increasing dab/dT, suggesting that the metallic term of c arises from misaligned Cu---O planes. This is confirmed by an electron-microscope (HRTEM) analysis of the samples. The anisotropy ratio c/ab is of the order of 103 but increases monotonically with decreasing temperature, indicating differences in the scattering processes parallel and perpendicular to the Cu---O plane. 相似文献
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提出了一种严格求解任意自旋-s算子幺正演化矩阵的方法,该方法不同于群论的方法和直接计算的方法,是一种间接的算法.方法的核心是利用两个系统表示的等价性:即自旋-s算子Hamiltonian量Hs=Sx与Heisenberg XX开链带相互作用Jn=n(N-n)的Hamiltonian量的等价性,由于存在这种等价性,自旋-s算子幺正演化矩阵的计算可通过Heisenberg XX开链中态的演化来实现.采用该方法计算了s=3/2,s=2和s=5/2时对应的幺正演化矩阵.由于初始态|sm〉在算子e-itSx下的演化实质上相当于对态|sm〉进行一个绕x轴转角为β=t的转动,演化矩阵元dsm'm(t)=〈sm′|e-itSx|sm〉就是转动后的态e-itSx|sm〉在|sm′〉态上的投影值,所以在t=π时刻的演化矩阵刚好对应Heisenberg XX开链上量子态的理想传输.
关键词:
s算子')" href="#">自旋-s算子
幺正演化矩阵
量子态传输 相似文献
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本文提出了予测稠苯芳杂环及其烷基链上质子化学位移的计算方法。
将稠苯芳杂环化合物用凯库勒式表示,计算式为为需考虑的苯环内的乙烯基效应。σmi,ci为各苯环的环流效应。σ1,Hc为各芳杂环的屏蔽效应,对杂环上质子它就是该单独芳杂环上相应质子的δ值,对苯环上质子要将它分解为各结构因素的效应,即:σ1,He=(1/2)d-1δx=y(或σz)+σc-c·σm,H.
σx-y与σz为杂原子或其基团的屏蔽效应,σc=c为存在于芳杂环中的乙烯基的效应,σm,Hc为芳杂环的环流效应,d为对不同质子所考虑的键数。有取代基时需考虑取代基的效应。计算环上烷基质子的公式为:δ=σp,CH3+ασc,CH3+βσt,CH3+σl,G
σl,G为稠苯芳杂环基的某级效应。 相似文献
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Paola Morando Concepción Muriel Adrián Ruiz 《Journal of Nonlinear Mathematical Physics》2019,26(2):188-201
The notion of solvable structure is generalized in order to exploit the presence of an algebra of symmetries for a kth-order ordinary differential equation with k > 3. In this setting, the knowledge of a generalized solvable structure for allows us to reduce to a family of second-order linear ordinary differential equations depending on k ? 3 parameters. Examples of explicit integration of fourth and fifth order equations are provided in order to illustrate the procedure. 相似文献
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本文用粉末烧结法合成了Tl-Ba-Ca-Cu-O体系TlBa2Can-1CunO2n+2.5新系列超导相,用粉末衍射法测定了n=2和3的晶体结构,属简单四方单胞,空间群为D4h1-P4/mmm,点阵常数a相同,而c值不同,随n值而增大。a=3.847?,c分别为12.73?和15.89?,每单胞含一个化合式单位,阳离子沿四方晶系的(0,0,z)和(1/2,1/2,z)位置交替排列,排列的顺序相同,n=3比n=2依次多增加Ca和Cu及相应的氧离子。TlBa2CanCunO2n+2.5,n=3时,零电阻超导转变温度Tc(0)=112K;n=2时,Tc(0)=101K,与Tl2Ba2Can-1CunO2n+4型体心四方晶胞超导相不同,TlBa2Can-1CanO2n+2.5结构中缺氧类钙钛矿型结构单元[Ba2Can-1CunO2n+1]仅被TI-O单层所隔开,当n相同时,Tl-O双隔层的体心四方单胞比Tl-O单层的简单四方单胞的超导转变温度高10K左右,这说明Tl-Ba-Ca-Cu-O体系中超导相的转变温度不仅与类钙钛矿结构单元的[CuO4]和[CuO5]的数目有关,而且与Tl-O的隔层数目有关。
关键词: 相似文献
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Helga Baum 《Journal of Geometry and Physics》1987,4(4):503-522
Let
(P) be the moduli space of irreducible connections of a G-principal bundle P over a closed Riemannian spin manifold M. Let DA be the Dirac operator of M coupled to a connection A of P and f a smooth function on M. We consider a smooth variation A(u) of A with tangent vector ω and denote Tω:=
(DA(u)−f) (u=0. The coefficients of the asymptotic expansion of trace (Tω · e-t(DA−f)2) near t=0 define 1-forms a(k)f, K=0, 1, 2, … on
(P). In this paper we calculate aa(0)f, a(1)f, a(2)f and study some of their properties. For instance using the 1-form a(2)f for suitable functions f we obtain a foliation of codimension 5 of the space of G-instantons of S4. 相似文献
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Chuan-Hung Chen 《Physics letters. [Part B]》2003,560(3-4):178-187
We study the nonresonant three-body decays of B+→D(*)−sK+π+ and Bd→Ds(*)−K0π+. We find that these decays can provide the information on the time-like form factors of D(*)sK. We also explicitly investigate Bd→Ds(*)−K*+ decays by discriminating the nonresonant contributions with the unknown D(*)s wave functions being fixed by the measured mode of Bd→Ds−K+. 相似文献
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MC与$lt;i$gt;M$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;+1$lt;/sub$gt;$lt;i$gt;AC$lt;/i$gt;$lt;sub$gt;$lt;i$gt;n$lt;/i$gt;$lt;/sub$gt;稳定性与电子特征的第一性原理研究 下载免费PDF全文
研究MC与Mn+1ACn(M=Sc, Ti, V, Cr, Mn; A=Al, Si, P, S; n=1, 2, 3)结构的稳定性与电子特征有利于探究三元层状结构Mn+1ACn稳定性的内在原因和设计新型Mn+1ACn结构. 第一性原理计算研究表明, M-3d与C-2p轨道间的电子转移对MC与Mn+1ACn 的形成焓有较大影响. 供电子能力较强的前过渡金属可以形成稳定的MC结构. 计算结果显示, MC结构是缺电子体系, 其趋向于与具有一定供电子能力的MA结构结合形成Mn+1ACn. 与M2PC和M2SC 相比, M2AlC和M2SiC可以更为容易地被分离成二维 M2C结构.
关键词:
MAX相结构
第一性原理
电子结构
过渡金属碳化物 相似文献
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The effects of an electric field on the interband transitions in InxGa1−xAs/InyAl1−yAs coupled step quantum wells have been investigated both experimentally and theoretically. A InxGa1−xAs/InyAl1−yAs coupled step quantum well sample consisted of the two sets of a 50 Å In0.53Ga0.47As shallow quantum well and a 50 Å In0.65Ga0.35As deep step quantum well bounded by two thick In0.52Al0.48As barriers separated by a 30 Å In0.52Al0.48As embedded potential barrier. The Stark shift of the interband transition energy in the InxGa1−xAs/InyAl1−yAs coupled step quantum well is larger than that of the single quantum well, and the oscillator strength in the InxGa1−xAs/InyAl1−yAs coupled step quantum well is larger than that in a coupled rectangular quantum well. These results indicate that InxGa1−xAs/InyAl1−yAs coupled step quantum wells hold promise for potential applications in optoelectron devices, such as tunable lasers. 相似文献
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《Journal of Nonlinear Mathematical Physics》2013,20(1):112-127
Abstract Let Vect(?) be the Lie algebra of smooth vector fields on ?. The space of symbols Pol(T*?) admits a non-trivial deformation (given by differential operators on weighted densities) as a Vect(?)-module that becomes trivial once the action is restricted to (2) ? Vect(?). The deformations of Pol(T*?), which become trivial once the action is restricted to (2) and such that the Vect(?)-action on them is expressed in terms of differential operators, are classified by the elements of the weight basis of , where denotes the differential cohomology (i.e., we consider only cochains that are given by differential operators) and where D λ,μ = Homdiff(F λ, F μ) is the space of differential operators acting on weighted densities. The main result of this paper is computation of this cohomology. In addition to relative cohomology, we exhibit 2-cocycles spanning and (2). 相似文献
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A reduced version of the Kogut-Susskind gauge theory is presented for U(∞) gauge theories. The reduced hamiltonian
, where Vij=trUiDiDjDj(UiDj) + (UiDj)+, is obtained by representing the group of space translations in the diagonal part of U(∞) U(∞). The space of states is invariant to the reduced gauge transformation Ui→ωUiDiω+Di+ and the scalar product carries a gauge invariant constraint on Ui The hamiltonian is also expr essed in terms of the string variables of Bars. We present the linear potential between static quarks at strong coupling and sketch the weak coupling expansion. 相似文献
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Tamara A. Leskova Ingve Simonsen Alexei A. Maradudin 《Waves in Random and Complex Media》2002,12(3):307-319
We study the statistical properties of the scattering matrix S(q|k) for the problem of the scattering of light of frequency ω from a randomly rough one-dimensional surface, defined by the equation x3=ζ(x1), where the surface profile function ζ(x1) constitutes a zero-mean, stationary, Gaussian random process. This is done by studying the effects of S(q|k) on the angular intensity correlation function C(q,k|q',k')=〈I(q|k)I(q'|k')〉-〈I(q|k)〉〈I(q'|k')〉, where the intensity I(q|k) is defined in terms of S(q|k) by I(q|k)=L-11(ω/c)|S(q|k)|2, with L1 the length of the x1 axis covered by the random surface. We focus our attention on the C(1) and C(10) correlation functions, which are the contributions to C(q,k|q',k') proportional to δ(q-k-q'+k') and δ(q-k+q'-k'), respectively. The existence of both of these correlation functions is consistent with the amplitude of the scattered field obeying complex Gaussian statistics in the limit of a long surface and in the presence of weak surface roughness. We show that the deviation of the statistics of the scattering matrix from complex circular Gaussian statistics and the C(10) correlation function are determined by exactly the same statistical moment of S(q|k). As the random surface becomes rougher, the amplitude of the scattered field no longer obeys complex Gaussian statistics but obeys complex circular Gaussian statistics instead. In this case the C(10) correlation function should therefore vanish. This result is confirmed by numerical simulation calculations. 相似文献
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I. Tanihata H. Hamagaki O. Hashimoto S. Nagamiya Y. Shida N. Yoshikawa 《Physics letters. [Part B]》1985,160(6):380-384
Secondary beams of 3He, 4He, 6He, and 8He were produced through the projectile fragmentation of an 800 MeV/nucleon 11B primary beam. Interaction cross sections (σI) of all He isotopes of 790 MeV/nucleon on Be, C, and Al targets were measured by a transmission-type experiment. The interaction nuclear radii of He isotopes RI(He) = (σI/π)1/2 − R I(T) where RI(T) is the radius of the target nucleus, have been deduced to be RI(3He) = 1.59 ± 0.06 fm, RI(4He) = 1.40 ± 0.05 fm, RI(6He) = 2.21 ± 0.06 fm, and RI(8He) = 2.52 ± 0.06 fm. 相似文献