Theoretical analysis of higher-order phonon sidebands in semiconductor luminescence spectra

A semiconductor luminescence formula is derived that includes phonon replica of arbitrary order based on a non-perturbative treatment of the electron–phonon interaction. The formula is used to analyze the extraordinarily strong sidebands observed with ZnO nanorods in recent experiments. Sidebands due to free and impurity-bound excitons are compared, and the generic differences between bulk and quantum-well emission are discussed.     

傅里叶变换光谱成像仪光谱传递函数研究

根据光学传递函数理论,定义了光谱成像仪的光谱传递函数. 针对基于Michelson干涉仪的时间调制傅里叶变换（FT）光谱成像仪,基于Sagnac干涉仪、Fresnel干涉仪、Lloyd干涉仪的空间调制FT光谱成像仪,推导出相应的光谱调制传递函数和光谱相位传递函数解析表达式,并分析了其物理意义. 光谱传递函数为评价相应光谱成像仪在光谱域的性能提供了一种量化的判据. 与空间域的光学传递函数相结合,成为反映光谱成像仪综合性能的客观依据. 关键词： 傅里叶变换 光谱成像仪 光谱传递函数     

Influence of a phonon bath in a quantum dot cavity QED system:Dependence of the shape

We present a systematic analysis on the role of the quantum dot （QD） shape in the influence of the phonon bath on the dynamics of a QD cavity QED system. The spectral functions of the phonon bath in three representative QD shapes： spherical, ellipsoidal, and disk, are calculated from the carrier wave functions subjected to the confinement potential provided by the corresponding shape. The obtained spectral functions are used to calculate three main effects brought by the phonon bath, i.e., the coupling renormalization, the off-resonance assisted feeding rate and the pure dephasing rate. It is found that the spectral function of a disk QD has the widest distribution, hence the phonon bath in a disk QD can lead to the smallest renormalization factor, the largest dephasing rate in the short time domains（≤2 ps）, and the oft-resonance assisted feeding can support the widest detuning. Except for the pure dephasing rate in the long time domains, all the influences brought by the phonon bath show serious shape dependence.     

Raman spectral probe on increased local vibrational modes and phonon lifetimes in Ho3+‐doped Bi2O3 micro‐rods

We report the appearance and enhancement in intensity of impurity related local vibrational modes in Bi₂O₃ : Ho micro‐rods along with normal modes. Pure and Ho‐doped Bi₂O₃ micro‐rods were synthesized by conventional co‐precipitation method at 60 °C. The structural and morphological studies were carried out using powder X‐ray diffraction technique and scanning electron microscopy, respectively. Raman spectroscopic studies reveal the existence of local phonon vibrational modes (LVM) due to the incorporation of Ho³⁺. Harmonic approximation method was employed to find the dopant‐related peak in the Raman spectra. Variation in full width at half maximum for LVM with increase in Ho³⁺ was also investigated. This increase in FWHM indicates the decrease in crystallinity of the doped samples. The phonon lifetime calculation carried out for each samples and the decrease in phonon lifetime with doping concentration make this material a potential candidate for optical and electronic applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of contact shape on ballistic phonon transport in semiconductor nanowires

We study the effects of contact shape on ballistic phonon transport in semiconductor nanowires at low temperatures using an approximative scalar model of continuum elasticity. Five different contacts connected to two semiconductor nanowires with different transverse widths are discussed. Numerical results show that the contact shape acts as an ‘acoustic impedance adaptor’, playing a crucial role on the ballistic phonon transmission and thermal conductance. The phonon coupling in the contacts with certain length facilitates ballistic phonon transmission compared to the abrupt interface, in which the phonon scattering is the strongest. It is found that the more the contact is abrupt, the smaller the thermal conductance is. The catenoidal contact rather than the abrupt interface is also the competitive candidate to obtain bigger thermal conductance. These results indicate that choosing an appropriate contact shape is one of the most critical factors to accurately measure the thermal conductance with a very high precision and reliability in different temperature ranges at low temperatures.     

The effect of a plasma microfield on hydrogen radiation near the thresholds of spectral series

The authors consider the dependence of hydrogen plasma radiation on the nonideality parameter near the thresholds of spectral series. At low electron concentrations experimental data agree well with calculations based on the principle of spectroscopic stability. At higher electron concentrations the experimental data agree better with calculations that include a decrease in the thresholds of photorecombination in the statistical plasma microfield and a change in the statistical weight of the levels which is induced by their autoionization in the plasma microfield. A. V. Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus, 15, P. Brovka St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 1, pp. 22–26, January–February, 1998.     

Pore-size dependence of the heat conduction in porous silicon and phonon spectral energy density analysis

Semiconductor devices made of silicon material have been widely used due to its excellent thermoelectrical properties. Here, the silicon material with aligned distributed rectangular-shaped holes is proposed for the manufacture of semiconductor device. Comprehensive understanding the heat conduction is of great significance to improve the efficiency of the thermoelectrical materials. This letter investigates the thermal conductivity of nanoscale porous silicon structures by adopting the nonequilibrium molecular dynamics method. The results demonstrate that the temperature is sensitive to the sizes of the rectangular-shaped holes. Additionally, it is found that the effective thermal conductivity significantly decreases with the increase of the dimensions of the holes. Our work reveals that the key to reduce the effective thermal conductivity is to disturb the distribution of heat flux. Furthermore, the phonon spectral energy density method is used to obtain the phonon dispersion and phonon energy in the frequency domain.     

高度电离的锗激光等离子体X射线谱的辨认

本文结合理论计算得到的锗类钠、类氖、类氟、类氧离子的振子强度,对平面晶体谱仪拍摄的锗激光等离子体X射线谱,波长在6～10(?)范围内的40多条谱线进行了分类辨认.     

声子色散对量子点中弱耦合磁极化子性质的影响(英文)

利用线性组合算符和幺正变换的方法,研究声子色散对磁场中抛物量子点弱耦合磁极化子性质的影响.计及LO声子色散,在抛物近似下导出了基态能量与量子点有效受限长度、声子色散系数、磁场强度以及耦合强度之间的关系.我们可以得到在弱耦合情况下抛物量子点中磁极化子的基态能量E0随量子点有效受限长度l0、电子声子耦合常数α和声子色散系数γ的增大而减小,随磁场回旋频率ωc增大而增大.自陷能Eotr随声子色散系数γ增大而增大.     

声子色散对量子点中弱耦合磁极化子声子平均数的影响

利用线性组合算符和幺正变换相结合的方法,研究了声子色散对抛物量子点中弱耦合磁极化子电子周围光学声子平均数的影响．计及纵光学(LO)声子色散,在抛物近似下导出了基态能量与量子点有效受限长度、声子色散系数、回旋共振频率以及电子-声子耦合常数之间的关系,电子周围光学声子平均数与声子色散系数以及电子-声子耦合常数的关系．数值计算结果表明在弱耦合情况下抛物量子点中磁极化子的基态能量随声子色散系数的增大而减小;电子周围光学声子平均数随声子色散系数增大而增大,随电子-声子耦合常数的增大而增大．     

声子色散对量子点中弱耦合磁极化子声子平均数的影响

利用线性组合算符和幺正变换相结合的方法,研究了声子色散对抛物量子点中弱耦合磁极化子电子周围光学声子平均数的影响。计及纵光学（ LO）声子色散,在抛物近似下导出了基态能量与量子点有效受限长度、声子色散系数、回旋共振频率以及电子－声子耦合常数之间的关系,电子周围光学声子平均数与声子色散系数以及电子－声子耦合常数的关系。数值计算结果表明在弱耦合情况下抛物量子点中磁极化子的基态能量随声子色散系数的增大而减小;电子周围光学声子平均数随声子色散系数增大而增大,随电子－声子耦合常数的增大而增大。     

Effect of quantization and positron concentration on shielding potentials in electron-positron-ion plasma

The kinetic theory of plasma has been employed to compute the test-charge potential distributions accounting for quantization effects in magnetized electron-positron-ion (EPI) plasmas. In this regard, the degenerate positrons and electrons are assumed to follow the Fermi-Dirac distribution, while inertial ions are modelled by Maxwellian velocity distribution. By solving the Fourier-transformed Vlasov–Poisson equations, a modified dielectric function and electrostatic potential is obtained. By imposing various constraints on the test-charge speed, the potential profile has been analysed in terms of Debye–Hückel (DH), far-field (FF), and wake-field (WF) potentials. It has been found that the amplitude of DH and FF potentials increases by the inclusion of quantization effects, and it becomes the opposite for the WF potential profile. Furthermore, the variation of positron concentration significantly affects the DH, FF, and WF potentials. The present findings are important to understand the shielding phenomenon in degenerate multi-species plasmas.     

边界条件对介电量子波导中声子输运性质的影响

运用散射矩阵方法，研究了Neumann边界条件和Dirichlet边界条件在低温下对结构不连续的纳米结构中的声学声子输运系数的影响.数值结果表明，当边界条件不同时，声学声子输运系数会有极大的不同；在一定的结构条件下，由于声子模与模的耦合作用，出现了共振透射和禁止频带.     

晶体中离子质量差异与激活离子光谱线热加宽和热位移

证明了基质晶体离子的质量差异对其中的激活离子光谱线的热加宽和热位移有贡献，对于单声子吸收或发射机制产生的热加宽和热位移而言，其贡献可以用一个乘积因子D^2表示，对于喇曼散射机制引起的热加宽，其贡献可以用乘积因子D^4表示，文中分别给出两种离子组成的晶体和三种离子组成的晶体的D的表示式。     

AlB2 and MgB2: a comparative study of their electronic,phonon and superconductivity properties via first principles

ABSTRACT

Recently, the AlB₂-type compounds (such as AlB₂ and MgB₂) which exhibit Dirac Nodal Line (DNLs) semimetal on their electronic band structure and Phononic Weyl Nodal Straight Lines (PTWNLs) on their phonon spectrum, have received wide attentions on their novel properties. Up to date, no comparative studies have been investigated on their electronic structures, phonon spectrum, and electron phonon coupling (EPC) under the conditions of carrier doping and strain engineering. Here, we systemically investigate their above properties under carrier doping and strain engineering by first-principles calculations. The results show that the superconducting transition temperature T _c can be enhanced by electron doping and tensile strain. For AlB₂, the tensile strain of 6% can enhance T _c to 10.25?K and with the doping concentrate of 0.1 e^- per cell can enhance T _c reach to 9.89?K. Moreover, the physical quantities related to superconductivity of AlB₂ are more affected by carrier doping than MgB₂. Our results provide a theoretical reference to explore the correlation between electronic and phonon topological properties in AlB₂-type materials.     

Analysis of electron energy distribution function in a magnetically filtered complex plasma

The electron energy distribution function (EEDF) for a magnetically filtered dusty plasma is studied in a dusty double plasma device where the electron energy can be varied from 0.15 eV to ～ 2.8 eV and plasma density from 10 6 cm-3 to 10 9cm-3 . The characteristics of EEDF for these ranges of plasma parameters are investigated in a pristine plasma as well as in a dusty plasma. The results show that in the presence of dust, there is a drastic modification in EEDF patterns in a plasma with higher electron temperature and density than those in a low temperature and low density plasma produced by the magnetic filter.     

Pair correlation function in a dense plasma and pycnonuclear reactions in stars

The short-range behavior of the pair correlation function in a dense onecomponent plasma (jellium) is investigated. As an intermediate step, the short-range behavior of the classical pair correlation function is obtained. Actually, although the temperature and the density are assumed to be such that the thermodynamic properties are almost classical, quantum mechanics (tunnel effect) always dominates the pair correlation function at short distances. The quantum pair correlation function is calculated by treating the many-body quantum effects by a perturbation theory, and by using a semiclassical approximation based on path integrals. The results are applied to the computation of the nuclear reaction rate in dense stellar matter (pycnonuclear reactions).Laboratoire associé au Centre National de la Recherche Scientifique.     

Interwire element of an impurity spectral function in coupled asymmetric quantum wires

We calculate the interwire element of the impurity spectral function in coupled double quantum wires at finite temperatures. Simple anisotropy in the direction perpendicular to the wires gives rise to this element, which is responsible for tunneling-induced effects. We find interwire particle–hole (single-particle) excitations contributing to the total impurity spectral function for temperatures up to 20 K.