共查询到20条相似文献,搜索用时 46 毫秒
1.
A band structure investigation of the bulk photovoltaic tensor for n-Gap is presented. It is based on a second-order quantum mechanical response formalism and the known electronic structure of GaP. The good agreement between experimental data and our numerical results demonstrates that the intrinsic bulk photovoltaic effect in GaP is related to an optically induced nonlinear interference phenomenon. 相似文献
2.
Sreemanta Mitra Amrita Mandal Anindya Datta Sourish Banerjee Dipankar Chakravorty 《Journal of magnetism and magnetic materials》2012
Nanosheets of nickel with thickness equal to 0.6 nm have been grown within the interlayer spaces of Na-4 mica. The sheets are made up of percolative clusters of nanodisks. Magnetization characteristics indicate a superparamagnetic behavior with a blocking temperature of 428 K. The magnetic anisotropy constant as extracted from the coercivity data has been found to be higher than that of bulk nickel by two orders of magnitude. This is ascribed to a large aspect ratio of the nickel nanophase. The Bloch exponent is also found to be considerably different from that of bulk nickel because of a size effect. The Bloch equation is still found to be valid for the two dimensional structures. 相似文献
3.
K. A. Verkhovskaya A. V. Vannikov A. D. Grishina A. S. Laryushkin V. V. Savel’ev T. V. Krivenko 《Technical Physics》2016,61(7):1109-1111
The photovoltaic properties and the bulk photovoltaic effect have been studied in a polyvinylidene difluoride–trifluoroethylene polymeric ferroelectric doped by single-walled nanotubes and a ruthenium-based dye. The dopants serve as spectral sensibilizers that improve sensitivity to 532-nm laser radiation. 相似文献
4.
Bloch oscillation and Landau\ben Zener tunnelling in a modulated optical lattice in a photovoltaic photorefractive crystal 下载免费PDF全文
We theoretically study the beam dynamical behaviour in a modulated optical lattice with a quadratic potential in a photovoltaic photorefractive crystal.We find that two different Bloch oscillation patterns appear for the excitation of both broad and narrow light beams.One kind of optical Landau–Zener tunnelling also appears upon the Bloch oscillation and can be controlled by adjusting the parameter of the optical lattice.Unlike the case of linear potential,the energy radiation due to Landau–Zener tunnelling can be confined in modulated lattices of this kind.For high input intensity levels,the Landau–Zener tunnelling is suppressed by the photovoltaic photorefractive nonlinearity and a symmetry breaking of beam propagation from the modulational instability appears. 相似文献
5.
H. Heyszenau 《Zeitschrift für Physik B Condensed Matter》1980,37(3):187-191
The response coefficient for the bulk photovoltaic effect is derived from second order response theory for free electrons as well as for diffusive carrier motion in low mobility systems. 相似文献
6.
电子在晶格周期性势场影响下的运动遵循布洛赫定理. 布洛赫电子除了具有电荷和自旋两个内禀自由度外, 还有其他内禀自由度. 能带色散曲线上的某些极值点作为谷自由度, 具有独特的电子结构和运动规律. 本文从布洛赫电子的谷自由度出发, 简单介绍传统半导体的谷电子性质研究现状, 并重点介绍新型二维材料体系, 如石墨烯、硅烯、硫族化合物等材料中谷相关的物理特性. 有效利用谷自由度的新奇输运特性, 将其作为信息的载体可以制作出新颖的纳米光电子器件, 并有望造就下一代纳电子器件的新领域, 即谷电子学(valleytronics). 相似文献
7.
Monte Carlo simulation of spin-wave excitation for the magnetic films with structure and interaction fluctuations 总被引:1,自引:0,他引:1
Monte Carlo simulation studies are performed to examine influence of structure and interaction fluctuations on magnetic properties of a ferromagnetic system modelled with a Heisenberg Hamiltonian. It is found that the spontaneous magnetization at low temperature for the multilayered films decreases with temperature in a Bloch law of spin-wave excitations. Both Bloch coefficient B and exponent b vary evidently because of a strong surface and size effect in the finite magnetic films with free boundaries. For the disordered bulk FCC magnet with periodic boundary, the Bloch T3/2 law is followed at low temperature and B is greatly influenced by the structure and interaction fluctuations. At the same time, Bloch coefficient B of the amorphous magnet with the coordination and interaction fluctuations has been derived. The simulated results are in good agreement with the theoretical predictions of spin-wave excitation, and explain the experimental facts well. 相似文献
8.
We present a quantum mechanical calculation of the bulk photovoltaic current in ferroelectrics which leads to the correct order of magnitude compared with experimental data. Our theory is based on the model of “asymmetric” transition probabilities which has been recently proposed by Glass to explain the anomalous photovoltaic effect in LiNbO3. 相似文献
9.
Modulation instability of quasi-plane-wave optical beams in biased photorefractive-photovoltaic crystals 下载免费PDF全文
We investigate the modulation instability of quasi-plane-wave optical beams in biased photorefractive-photovoltaic crystals by globally treating the space-charge field. The modulation instability growth rate is obtained, which depends on the external bias field, on the bulk photovoltaic effect, and on the ratio of the optical beam's intensity to that of the dark irradiance. Our analysis indicates that this modulation instability growth rate is identical to the modulation instability growth rate studied previously in biased photorefractive-nonphotovoltaic crystals when the bulk photovoltaic effect is negligible for shorted circuits, and predicts the modulation instability growth rate in open- and closed-circuit photorefractive-photovoltaic crystals when the external bias field is absent. 相似文献
10.
采用振幅掩模穿过部分空间非相干光的方法产生一暗迹,将暗迹成像在晶体前表面,得到入射暗迹半高宽为16.75 μm,入射光功率为400 μW.基于LiNbO3:Fe晶体的强光伏效应,在无背景光辐照时,在晶体内写入一对部分空间非相干Y结暗光伏孤子.实验结果表明:在无背景光辐射时可以在LiNbO3:Fe晶体内写入部分空间非相干Y结孤子. 相似文献
11.
利用GC Valley的准连续光(Quasi-cw)近似模型,研究了短脉冲激光(纳秒ns量级)在光伏光折变材料LiNbO3晶体中写入和擦除光折变光栅的过程,给出了空间电荷场随时间变化的表达式.理论研究表明,空间电荷场的形成和擦除与两个时间参量有关,在考虑或者不考虑光生伏打效应两种情况下,这两个参量随擦除光强的变化有基本相同的变化规律,光栅的写入和擦除有相同的结果.同样,擦除一个光栅所需的光能量在两种情况下也有相同的结果.因此,在短脉冲光入射光折变晶体材料情况下,考虑光生伏打效应与不考虑光伏效应,对短脉冲光在光折变LiNbO3晶体中写入和擦除光栅基本没有影响. 相似文献
12.
V. M. Fridkin 《Applied Physics A: Materials Science & Processing》1977,13(4):357-359
The bulk photovoltaic effect and the photorefractive effect in some oxygen octahedra ferroelectrics (e.g., LiNbO3, KNbO3, (Sr, Ba) Nb2O6, BaTiO3) are interpreted on the base of the fluctuations model. The kinetics of the photovoltaic effect and its temperature and lux-ampere
characteristic are investigated. 相似文献
13.
Photovoltaic and Electroluminescence Characters in Hybrid ZnO and Conjugated Polymer Bulk Heterojunction Devices 下载免费PDF全文
We report electroluminescence in hybrid ZnO and conjugated polymer poly[2-methoxy-5-(3′, 7′-dimethyloctyloxy)- 1,4-phenylenevinylene] (MDMO-PPV) bulk heterojunction photovoltaic cells. Photoluminescence quenching experimental results indicate that the ultrafast photoinduced electron transfer occurs from MDMO-PPV to ZnO under illumination. The ultrafast photoinduced electron transfer effect is induced because ZnO has an electron affinity a bout 1.2 e V greater than that of MDMO-PP V. Electron 'back transfer' can occur if the interfacial barrier between ZnO and MDMO-PPV can be overcome by applying a substantial electric field. Therefore, electrolumi- nescence action due to the fact that the back transfer effect can be observed in the ZnO:MDMO-PPV devices since a forward bias is applied. The photovoltaic and electroluminescence actions in the same ZnO:MDMO-PPV device can be induced by different injection ways: photoinjection and electrical injection. The devices are expected to provide an opportunity for dual functionality devices with photovoltaic effect and electroluminescence character. 相似文献
14.
15.
Tenghui Wang Zhenxing Zhang Liang Xiang Zhihao Gong Jianlan Wu Yi Yin 《中国科学:物理学 力学 天文学(英文版)》2018,61(4):047411
The significance of topological phases has been widely recognized in the community of condensed matter physics. The well controllable quantum systems provide an artificial platform to probe and engineer various topological phases. The adiabatic trajectory of a quantum state describes the change of the bulk Bloch eigenstates with the momentum, and this adiabatic simulation method is however practically limited due to quantum dissipation. Here we apply the “shortcut to adiabaticity” (STA) protocol to realize fast adiabatic evolutions in the system of a superconducting phase qubit. The resulting fast adiabatic trajectories illustrate the change of the bulk Bloch eigenstates in the Su-Schrieffer-Heeger (SSH) model. A sharp transition is experimentally determined for the topological invariant of a winding number. Our experiment helps identify the topological Chern number of a two-dimensional toy model, suggesting the applicability of the fast adiabatic simulation method for topological systems. 相似文献
16.
17.
18.
The oscillatory motion of electrons in a periodic potential under a constant applied electric field, known as Bloch oscillations (BO), is one of the most striking and intriguing quantum effects and was predicted more than eighty years ago. Oscillating electrons emit electromagnetic radiation and here we consider this BO effect for emission in the THz region. To date, it has been assumed that the Bloch oscillation of an electron is anharmonic oscillation, therefore with radiation emitted at the single Bloch frequency. We analyze scenarios when Bloch oscillations can be accompanied by the emission of radiation not only at the Bloch frequency but also with double and triple Bloch frequencies. The first scenario means that electrons could jump over neighboring Stark states. The second scenario of anharmonic emission is coupled to an opening of the minigap in the miniband. 相似文献
19.
Initial formation and subsequent development of the electronic structure in band-by-band detail are studied for epitaxial palladium overlayers deposited onto a copper (1 1 1) single crystal substrate. Two-dimensional Bloch states are found to be established at the first full monolayer. The three-dimensional Bloch states characteristic of the Pd bulk crystal begin to be observed upon completion of the second layer. A surface sensitive Pd- derived feature is found to be formed at coverages of two monolayers. 相似文献
20.
Working in the Wannier representation, we derive an expression for the orbital magnetization of a periodic insulator. The magnetization is shown to be comprised of two contributions, an obvious one associated with the internal circulation of bulklike Wannier functions in the interior, and an unexpected one arising from net currents carried by Wannier functions near the surface. Each contribution can be expressed as a bulk property in terms of Bloch functions in a gauge-invariant way. Our expression is verified by comparing numerical tight-binding calculations for finite and periodic samples. 相似文献