关键词： SCATTERING (Physics)   QUANTUM dots   ELECTRONIC apparatus & appliances   BALLISTIC electrons -- Mathematical models   ELECTRON transport   DOPING agents (Chemistry)   TEMPERATURE effect  

摘要： Disorder increasingly affects performance as electronic devices are reduced in size. The ionized dopants used to populate a device with electrons are particularly problematic, leading to unpredictable changes in the behavior of devices such as quantum dots each time they are cooled for use. We show that a quantum dot can be used as a highly sensitive probe of changes in disorder potential and that, by removing the ionized dopants and populating the dot electrostatically, its electronic properties become reproducible with high fidelity after thermal cycling to room temperature. Our work demonstrates that the disorder potential has a significant, perhaps even dominant, influence on the electron dynamics, with important implications for “ballistic” transport in quantum dots.

关键词： 磁性   介电   磁电耦合   量子顺电  

摘要： 由于磁性和介电性质的强烈耦合,量子顺电材料EuTiO_3材料的研究近来倍受人们的关注.本文通过运用基于密度泛函理论的第一性原理计算研究了量子顺电(PE)材料EuTiO_3的磁性和电子结构,分析了应变对磁性和结构相变的作用,从而探讨了该材料中可能的磁电耦合机理.结果发现,在无应变状态下,EuTiO_3处于顺电立方-G型反铁磁性态,而对于c轴方向的无论张应变还是压应变,当应变增加到一定程度时,由于Ti 3d空轨道与周围O2p电子的杂化平衡被打破,EuTiO_3将相变到铁电(FE)四方-铁磁结构,显示了强烈的自旋一晶格耦合效应.

关键词： 含能材料   量子化学计算   分子动力学模拟   综述  

摘要： 从含能材料分子的热力学性质及爆轰性能、分解机理、感度、分子间相互作用及相容性、固体与界面性质和极端条件下的性质几个方面,综述量子化学(QC)和分子动力学模拟(MD)方法在含能材料中的应用。所涉及的方法主要为量子化学第一性原理和经典分子动力学模拟(包括分子反应动力学模拟),比较了各种方法的特点和适用范围,列举了一些典型实例。附参考文献57篇。

关键词： 铁磁电极   量子点   A-B环  

摘要： 运用Keldysh格林函数方法,研究了两端联有铁磁电极的A-B环中的双量子点自旋极化输运.研究结果显示,系统的隧穿电流、自旋向上电流、自旋向下电流以及自旋累积明显的受自旋极化强度、外加电压和磁通的影响,并且随着极化强度的增大,在平行与反平行组态下的隧穿电流都减小,另外还出现了自旋分流现象.通过改变磁通,能明显地观察到两条通道的干涉现象.反平行组态下的自旋累积会随着极化强度的增大而增大.

关键词： 纤锌矿   量子阱   极化子  

摘要： 采用Lee-Low-Pines(LLP)变分法研究纤锌矿量子阱材料中电子-声子相互作用有关问题,给出纤锌矿GaN/AlxGa1-xN和InxGa1-xN/GaN量子阱材料中极化子基态能量和第一激发态到基态的跃迁能量随量子阱宽度和材料组分的变化关系.研究中考虑了纤锌矿量子阱材料中光学声子模各向异性以及声子频率随波矢的变化关系.同时还对运用LLP变分方法计算极化子能量时所采用的几种不同处理方法进行了分析和讨论,并给出相应的数值计算结果.

关键词： thermoelectrics   nanocomposites   quantum dot   electronic band structure   Lorenz number  

摘要： Following the idea that there exists an optimal bandwidth for maximizing the thermoelectric figure of merit (ZT), we conduct detailed calculations in this paper to search for the optimal ZT in Bi2Te3/Sb2Te3 quantum dot (QD) nanocomposites (NCs) with Bi2Te3 QDs uniformly embedded in Sb2Te3 matrix where electron minibands are formed. The two-channel transport model, which considers both the miniband transport by the quantum-confined carriers and the background transport by the bulklike carriers, is used for electrical transport, while the lattice thermal conductivity is modeled using the modified effective medium approximation. Simultaneous decrease of the lattice thermal conductivity and the Lorenz number leads to an enhanced ZT in QD NCs when the Seebeck coefficient is not dramatically decreased. The optimal structural parameters that result in optimal electronic structure for maximizing ZT are found, with the consideration of realistic carrier scattering physics including phonon bottleneck effect. The optimal QD size is found to be ∼6nm, and the optimal interdot distance depends on the QD size and the doping concentration. For a given QD size, the maximum ZT is determined by the minimum of Lorenz number, which occurs when the quantum-confined carrier transport overwhelms the bulklike carrier transport.

关键词： 非均匀结构   弹性波   声学声子输运   热导  

摘要： 利用散射矩阵方法,研究非均匀结构调制的半导体量子波导中6支最低弹性声子模的输运系数与热导性质。研究结果表明:当4支最低声学声子模的截止频率为0Hz且当频率接近于0Hz时,透射系数总为1;当2支光学模的截止频率大于0Hz且当频率接近截止频率时,透射系数总为0;声子模的输运系数、量子化热导平台以及热导性质与量子点的结构密切相关;在极低温度下,扭转模的热导对结构最敏感,而随着温度的增大,压缩模与y方向的弯曲声学模的热导对量子点的结构最敏感;改变量子点的结构能有效调节6支单模的热导。

关键词： 量子输运   叠加石墨烯纳米带   第一性原理   格林函数  

摘要： 用基于第一性原理的密度泛函理论和非平衡格林函数理论的计算模拟方法研究了不同宽度错层叠加锯齿边缘型石墨烯纳米带(ZGNRs)的电子输运特性.与单层ZGNRs相比,错层叠加ZGNRs中存在层间界面,因而在该系统中能够实现更加丰富的电学特性.研究表明,错层叠加ZGNRs中能较容易实现负微分电阻现象.这使得错层叠加ZGNRs有可能被用来制作电子振荡器件.

关键词： 量子力学   教学研究   哲学思想  

摘要： 本文结合材料物理专业中的基础课程——《量子理论》的发展史,从哲学的角度出发,浅谈了材料学科发展中的哲学思想,并以哲学思想为主线,来进一步指导学生对现代科学技术发展的理解,对加强学生的世界观、物质观以及运动观的进一步理解,具有重要的指导意义。

关键词： s-Tetrazine   Density functional theory   Heat of formation   Bond dissociation energy   Density  

摘要： s-Tetrazine is the essential candidate of many energetic compounds due to its high nitrogen content, enthalpy of formation and thermal stability. The present study explores the design of s-tetrazine derivatives in which different -NO2, -NH2, and -N-3 substituted azoles are attached to the tetrazine ring via C-N linkage. The density functional theory (DFT) is used to predict the geometries, heats of formation (HOFs) and other energetic properties. The predicted results show that azide group plays a very important role in increasing HOF values of the s-tetrazine derivatives. The densities for designed molecules were predicted by using the crystal packing calculations. The introduction of -NO2 group improves the density as compared to -N-3, and -NH2 groups and hence the detonation performance. Bond dissociation energy analysis and insensitivity correlations revealed that amino derivatives are better candidates considering insensitivity and stability.