共查询到17条相似文献,搜索用时 312 毫秒
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利用负本征值理论的态密度计算方法,研究了准一维双链无序系统的电子结构。并针对系统大小,对角和非对角无序程等各种参数,探讨了电子的局域化,系统能量分布范围等问题。在引进无序参量后,对角无序主要引起电子局域态的增多,而非对角无序则使系统的能量分布范围发生变化。 相似文献
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对形如Nt×Nl型准二维无序系统,只考虑格点之间的最近邻跳跃积分,采用特殊的格点编号方案,在单电子近似下,系统的哈密顿量可表示为简明对称矩阵,借助豪斯荷尔德变换将其约化为对称三对角矩阵,再利用负本征值理论及传输矩阵等方法,对系统态密度、局域长度及电导等电子结构特性进行数值计算. 重点研究了准一维四平行链和五平行链无序系统, 将结果与一维单链、准一维双链及三链系统进行对比,发现随维度的增加,系统的能带有所展宽,能态密度分布发生很大的变化,其峰值数量呈偶数规律增加. 并且在能带中心处存在有局域长度大于系统大小的扩展态,处于这些态下的系统具有较大电导. 从单链到多链,相当于扩大了系统的关联范围,使系统出现了类似非对角长程关联的行为.
关键词:
准二维无序系统
态密度
局域长度
电导 相似文献
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在单电子紧束缚近似下,建立了准一维多链无序体系直流、交流电子跳跃输运模型,通过计算探讨了无序模式、维度效应、温度及外场对其直流、交流电导率的影响.计算结果表明:准一维多链无序体系的直流、交流电导率随着格点能量无序度的增大而减小,非对角无序具有增强体系电子输运能力的作用.随着链数的增加,体系的直流、交流电导率增大,但格点能量无序度较小时,维度效应的影响不明显.在对角无序情况下准一维多链无序体系的交流电导率随温度的升高而增大,而在非对角无序模式下却随温度的升高而减小,但对于直流情况,体系的直流电导率随温度的升 相似文献
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从单电子紧束缚模型的哈密顿量出发,格点能量随机取εA和εB,只计及格点之间的近程跳跃积分,建立了一维无序二元固体模型. 利用负本征值理论及无限阶微扰理论,对系统电子的本征值和本征态进行了数值计算. 结果表明与一定能量本征值对应的电子波函数只分布在系统的一定范围内,显示了其局域性. 借助传输矩阵方法,计算出电子的局域长度,讨论了局域长度随本征能量和无序度的变化关系,并研究了计入不同范围跳跃积分下,局域长度的变化特征.
关键词:
无序
二元固体
电子态
局域长度 相似文献
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在单电子紧束缚无序模型基础上,建立了一维二元非对角关联无序体系电子跳跃输运交流电导模型,并推导了其交流电导公式,通过计算其交流电导率,探讨了格点能量无序度、格点原子组分、非对角关联及温度、外场对体系交流跳跃电导的影响.计算结果表明,一维二元非对角关联无序体系的交流电导率随格点能量无序度的增大而减小.同时,体系中两种原子的组分的变化实际代表着体系成分无序程度的变化,因而对其交流电导率的影响很大,表现为随A类原子含量p的增加而先减小后增大.当引入非对角关联时,体系出现退局域化现象,电子波函数由局
关键词:
二元无序体系
交流跳跃电导
格点能量无序度
非对角关联 相似文献
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利用傅里叶滤波法在一维Anderson无序系统中产生了具有幂律谱密度公式s(q)∝q-p形式的长程关联随机能量序列,并利用传输矩阵方法计算了系统中引入了长程关联后的局域长度,同时应用负本征值理论对系统中的电子态密度进行了分析,并分别把计算结果与系统中不具有长程关联时的局域长度与电子态密度进行了比较.结果表明,长程幂律关联的引入对电子态的性质产生了很大的影响,当关联指数p≥2.0时,在系统能带中心范围内发生了部分局域态向退局域态的转变,而同时电子态密度也发生了很大的变化,出现了六个范霍夫奇点,系统的能带范围也相应地得到展宽.
关键词:
无序系统
长程关联
局域长度
电子态密度 相似文献
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在单电子紧束缚无序模型基础上,建立了一维二元关联无序体系电子跳跃输运直流电导模型,并推导了其直流电导公式,通过计算其直流电导率,探讨了格点能量无序度、非对角关联及温度、外场对体系跳跃电导的影响.计算结果表明,一维二元无序体系的直流电导率随着格点能量无序度的增大而减小;当引入非对角关联时,体系出现退局域化现象,从而使体系的直流电导率增大;温度对体系的电子输运的影响表现为体系的直流电导率随温度的升高而增大;在外加电场的调制下,体系的直流电导率在强场区随电场强度增加而增长很快,呈现出非欧姆定律特性,但在弱场区外场的作用不明显.
关键词:
二元无序体系
跳跃电导
格点能量无序度
非对角关联 相似文献
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Based on a tight-binding disordered model describing a single electron band,
we establish a direct current (dc) electronic hopping transport conductance
model of one-dimensional diagonal disordered systems, and also derive a dc
conductance formula. By calculating the dc conductivity, the relationships
between electric field and conductivity and between temperature and
conductivity are analysed, and the role played by the degree
of disorder in electronic
transport is studied. The results indicate the conductivity of systems
decreasing with the increase of the degree of disorder, characteristics of
negative differential dependence of resistance on temperature at low
temperatures in diagonal disordered systems, and the conductivity of systems
decreasing with the increase of electric field, featuring the non-Ohm's law
conductivity. 相似文献
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In the chain compound PrBa2Cu4O8 localization appears simultaneously with a dimensional crossover in the electronic ground state when the scattering rate in the chains exceeds the hopping rate between the chains. Here we report the discovery of a large, transverse magnetoresistance in PrBa2Cu4O8 in the localized regime. This result suggests a novel form of localization whereby electrons retain their metallic (quasi-one-dimensional) character over a microscopic length scale despite the fact that, macroscopically, they exhibit localized (one-dimensional) behavior. 相似文献
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We study numerically the localization properties of a two-channel quasi-one-dimensional Anderson model with uncorrelated diagonal disorder within the nearest-neighbor tight-binding approximation. We calculate and analyze the disorder-averaged transmittance and the Lyapunov exponent. We find that the localization of the entire system is enhanced by increasing the interchain hopping strength t?. From the numerical investigation of the energy dependence of the Lyapunov exponent for many different interchain hopping strengths, we find that apart from the band center anomaly, which usually occurs in strictly one-dimensional disordered systems, additional anomalies appear at special spectral points. They are found to be associated with the interchain hopping strength and occur at E = ± t?/2 and ± t?. We find that the anomalies at E = ± t? are associated with the π-coupling occurring within one energy band and those at E = ± t?/2 are associated with the π-coupling occurring between two different energy bands. Despite having a similar origin, these two anomalies have distinct characteristics in their dependence on the strength of disorder. We also show that for a suitable range of parameter values, effectively delocalized states are observed in finite-size systems. 相似文献
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F. Constantinescu G. Felder K. Gawedzki A. Kupiainen 《Journal of statistical physics》1987,48(3-4):365-391
Then-orbital gauge-invariant model of disordered electronic systems proposed by Wegner is studied in the regime of dominant diagonal disorder. Analyticity of the density of states is established in two cases: (a) when the number of orbitals is small, (b) when the number of orbitals is large and the energy is in the expected extended states region. 相似文献
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一维Anderson无序模型电子局域态 总被引:2,自引:1,他引:1
本文应用一种新方法,得到了包括次近邻相互作用,且无序点阵从五百到一万的一维安德逊无序模型电子本征态。结果表明此模型的本征态随着无序点阵的增加均从扩展态变为局域态,且变化的快慢受系统无序度的影响。 相似文献