GaAs/AlxGa1-xAs超晶格在周期性磁场中电子的能带结构

在有效质量理论近似下,采用磁Kronig-Penny势场,精确求解了GaAs/AlxGa1-xAs超晶格中的电子在周期性磁场中形成的能带结构.考虑不同方向上的周期性磁调制以及电调制的作用下三维电子的运动行为,发现电子不仅在z方向形成能带,而且在y方向也可以形成一些可允许的能带.同时详细讨论了电子能带结构的特点及其形成机制.     

布洛赫电子在磁场中之运动

本文导出布洛赫电子在磁场中简约波矢随时间变化之基本公式,在推导过程中,假设电子恒运动于一个能带中,因而忽略了跃迁至其它能带之可能。     

轴向磁场对锯齿型和扶手椅型碳纳米卷电子结构的影响

碳纳米卷作为一种新型的碳基纳米材料,其结构非封闭且内径大小容易调控,成为当今材料科学研究热点之一。利用石墨烯碳原子轨道作sp2杂化时π电子的紧束缚模型,考虑波矢k周期性边界条件及轴向磁场的影响,构造了磁场中碳纳米卷的紧束缚模型,并研究了其在轴向磁场中的能带、能隙及电子态密度等性质。结果表明,碳纳米卷的能量色散是以磁通量子Φ0为周期随磁通量Φ变化,最低未占据分子轨道也随之产生了明显移动,从而导致碳纳米卷发生金属-半导体连续转变,其中ZCNS(15,0)能隙最大为0.878 e V,而ACNS(12,12)为0.654 e V     

磁场中环状碳纳米卷电子结构的紧束缚法研究

通过考虑波矢■周期性边界条件,在石墨烯紧束缚模型基础上,构造了磁场中环状碳纳米卷模型,研究了其电子结构性质.结果表明环状碳纳米卷的电子结构以磁通量子Φ_0为周期随磁通量Φ周期性变化,通过控制手性和磁场,可将其调制成金属或不同带隙的半导体,其中m=3I(I为整数)、θ=2π/3的锯齿型环状碳纳米卷的带隙受磁场的影响比较小,m=18时变化幅度仅为7 μeV.     

磁场对单壁碳纳米管电子结构的影响

利用"石墨近似",讨论了施加轴向匀强磁场对理想单壁碳纳米管电子结构的影响,建立了相应模型并采用π电子紧束缚近似法,对Zigzag型碳管进行了理论分析与计算.计算表明磁场中SWNTs的子能带和磁通量是量子化的,其能带以磁通量子φ0为周期随磁通φ作周期性变化;并出现金属-半导体性的周期性转变现象.     

周期性磁场下的GaAs/AlxGa1-xAs单量子阱中电子的能带结构

为了研究外磁场对量子阱中电子的能带结构的影响，采取一种简单的可解析求解的模型，研究了周期性磁场下的ＧａＡｓ／ＡｌｘＧａ１－ｘＡｓ单量子阱中电子的能带结构，发现在周期性磁场的作用下，在ｚ方向上的能量是分立的量子化能级，而原来在ｘ－ｙ平面内连续的能级分裂成分立的一系列许可带，但是在ｘ方向上能量仍然是连续的，同时对其能带的特点和形成机制进行探讨。     

磁场对体心立方双层铁磁性薄膜中的自旋波能谱的影响

采用界面重参数化方法,在周期性边界条件下严格求解了界面铁磁耦合的体心立方异质型双层铁磁性薄膜自旋波本征值问题,研究了两层薄膜中自旋波能带结构.在此基础上重点讨论了垂直于膜面的外加磁场对自旋波能带结构的影响,结果表明,磁场对自旋波的能带结构有很大的影响,足够大的磁场可以使体模消失.     

电子声子相互作用对Graphene能带的修正

研究了电子声子相互作用对Graphene电子能带的影响,把电子和LO光频声子相互作用当作微扰,用微扰论方法计算了电子声子相互作用对电子能带的修正.计算结果表明,在费米面附近,Graphene电子能带下移,电子费米速度下降.计算结果和实验测量基本符合.     

外磁场对铁磁双层膜自旋波能带的影响

研究了在外磁场作用下铁磁双层薄膜材料中自旋波的本征值问题.采用界面重参数化方法,在周期性边界条件下,严格求解系统的三种本征模,并给出横向自旋波取全部值的能带结构图,讨论了外磁场对自旋波能带的影响.     

铁电180°畴超格子中的子能带

研究了铁电180°畴超格子中畴子对导带底电子特性的影响.这种影响将导致在这种结构中形成电子子能带,从而影响材料的电子特性.电子有效质量的增加将使子能带向畴子低频所形成的子能带方向移动.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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