Inertial spin Hall effect in non-commutative space

In the present Letter the study of inertial spin current (that appears in an accelerated frame of reference) is extended to Non-Commutative (NC) space. In the Hamiltonian framework, the Dirac Hamiltonian in an accelerating frame is computed in the low energy regime by exploiting the Foldy–Wouthuysen scheme. The NC θ-effect appears from the replacement of normal products and commutators by Moyal ?-products and ?-commutators. In particular, the commutator between the external magnetic vector potential and the potential induced by acceleration becomes non-trivial. Expressions for θ-corrected inertial spin current and conductivity are derived explicitly. We have provided yet another way of experimentally measuring θ. The θ bound is obtained from the out of plane spin polarization, which is experimentally observable.     

Dynamics of bound vector solitons induced by stochastic perturbations: Soliton breakup and soliton switching

We respectively investigate breakup and switching of the Manakov-typed bound vector solitons (BVSs) induced by two types of stochastic perturbations: the homogenous and nonhomogenous. Symmetry-recovering is discovered for the asymmetrical homogenous case, while soliton switching is found to relate with the perturbation amplitude and soliton coherence. Simulations show that soliton switching in the circularly-polarized light system is much weaker than that in the Manakov and linearly-polarized systems. In addition, the homogenous perturbations can enhance the soliton switching in both of the Manakov and non-integrable (linearly- and circularly-polarized) systems. Our results might be helpful in interpreting dynamics of the BVSs with stochastic noises in nonlinear optics or with stochastic quantum fluctuations in Bose–Einstein condensates.     

ESTIMATIONS OF THE CONSTANTS IN INVERSE INEQUALITIES FOR FINITE ELEMENT FUNCTIONS

In this paper, we estimate the constants in the inverse inequalities for the finite ele- ment functions. Furthermore, we obtain the least upper bounds of the constants in inverse inequalities for the low-order finite element functions. Such explicit estimates of the con- stants can be used as computable error bounds for the finite element method.     

Ultimate Charge Extraction of Monolayer PbS Quantum Dot for Observation of Multiple Exciton Generation

Multiple exciton generation (MEG) has great potential to improve the Shockley-Queisser (S-Q) efficiency limitation for colloidal quantum dot (CQD) solar cells. However, MEG has rarely been observed in CQD solar cells because of the loss of carriers through the transport mechanism between adjacent QDs. Herein, we demonstrate that excess charge carriers produced via MEG can be efficiently extracted using monolayer PbS QDs. The monolayer PbS QDs solar cells exhibit α=1 in the light intensity dependence of the short-circuit current density J_sc (J_sc∝I^α) and an internal quantum efficiency (IQE) value of 100 % at 2.95 eV because of their very short charge extraction path. In addition, the measured MEG threshold is 2.23 times the bandgap energy (E_g), which is the lowest value in PbS QD solar cells. We believe that this approach can provide a simple method to find suitable CQD materials and design interface engineering for MEG.     

Inequivalent Quantization in the Field of a Ferromagnetic Wire

We argue that it is possible to bind neutral atom (NA) to the ferromagnetic wire (FW) by inequivalent quantization of the Hamiltonian. We follow the well known von Neumann’s method of self-adjoint extensions (SAE) to get this inequivalent quantization, which is characterized by a parameter Σ∈ℝ(mod2π). There exists a single bound state for the coupling constant η ²∈[0,1). Although this bound state should not occur due to the existence of classical scale symmetry in the problem. But since quantization procedure breaks this classical symmetry, bound state comes out as a scale in the problem leading to scaling anomaly. We also discuss the strong coupling region η ²<0, which supports bound state making the problem re-normalizable.     

Binding Energy of Excitons in a Quantum Ring

The binding energy of excitons confined to a quantum ring under the influence of perpendicular homogeneous magnetic field is calculated as a function of the ring radius. Calculations are made by using the method of exact diagonalization within the effective-mass approximation. The feature of binding energy of the ground state as a function of the ring radius for several values of the magnetic field has been revealed. The interesting feature of our study is that, in a quantum ring, the geometric structure of exeitons may reveal transition.     

Radioluminescence and thermoluminescence properties of X-ray-irradiated pure CsI

The 25–280 K radioluminescence (RL) and thermoluminescence (TL) spectra in a nominally pure CsI have been studied. Strong emissions at 250–400 nm consist of two bands at 305 and 340 nm associated with the V_K+e and H+F-type self-trapped excitons (STEs), respectively. There are some weak extrinsic signals in RL. The temperature dependence and the response of the two main bands to the X-ray tube voltage have been studied. It has been found that the dominant TL signals are associated with contamination of the sample, though the trapping levels are still characterised by the host lattice. A temperature shift between the intrinsic and extrinsic TL peaks has been observed in the thermal emissions at 55 and 82 K.     

Time-resolved spectroscopy of freestanding GaN layers grown by halide vapour phase epitaxy

Freestanding GaN layers of various thicknesses grown by HVPE have been studied by time-resolved spectroscopy combined with structural and electrical measurements. We have observed an increase of the PL lifetime with increasing layer thickness; however, a saturation of the recombination times has been detected for the GaN layers thicker than 400 μm. We explain the observed thickness-dependent behavior of the decay times by competition of two nonradiative mechanisms; namely, for layers with thickness less than 400 μm the main nonradiative channel is related to the structural defects, while in thicker layers the recombination decay time is limited by impurities and/or vacancies.     

激子旋转弛豫对低掺杂卟啉侧链聚合物荧光衰变过程的影响

利用激子旋转扩散理论研究了一类低掺杂卟啉侧链聚合物中卟啉侧链基团的旋转对其发光动力学过程的影响.研究表明,卟啉侧链基团的旋转行为是导致激发态无辐射能量弛豫的重要途径.基团旋转越容易,能量弛豫速度越快,这可导致一个快速的荧光衰变动力学过程.在卟啉低掺杂浓度和聚合物分子链间距离较大的情况下,卟啉侧链基团的旋转成为影响荧光寿命和发光效率的主要因素.对实验测得的两种样品的荧光弛豫过程进行了拟合,理论结果与实验结果符合较好. 关键词： 激子旋转弛豫 瞬态荧光 卟啉侧链聚合物     

掺杂ZnSe/BeTe Ⅱ型量子阱结构中带电激子的磁场效应

报道了n型掺杂ZnSe/BeTe/ZnSe Ⅱ型量子阱(type-Ⅱ QW)在极低温 (5—10 K)条件下的各种光学性质. 磁场中(Farada配置)ZnSe层的反射光谱展示了一个典型的负的带电激子(X^-)的跃迁特征. 对于空间间接光致发光(spacially indirect PL)光谱,它的主发光峰显示了一个反玻尔兹曼分布的非对称性,并且在磁场中(Voigt配置)它的峰值能量随磁场的增加而降低. 这些实验结果显示了该掺杂样品的空间间接PL是来自Ⅱ型QW结构所特有的带电激子的跃迁. 关键词： 光致发光 二维电子气 带电激子 Ⅱ型量子阱