- 标题
- 摘要
- 关键词
- 实验方案
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Control of a spin qubit in a lateral GaAs quantum dot based on symmetry of gating potential
摘要： We study the influence of quantum dot symmetry on the Rabi frequency and phonon-induced spin relaxation rate in a single-electron GaAs spin qubit. We find that anisotropic dependence on the magnetic field direction is independent of the choice of the gating potential. Also, we discover that relative orientation of the quantum dot, with respect to the crystallographic frame, is relevant in systems with C1v, C2v, or Cn (n ≠ 4r) symmetry. To demonstrate the important impact of the gating potential shape on the spin qubit lifetime, we compare the effects of an infinite-wall equilateral triangle, square, and rectangular confinement with the known results for the harmonic potential. In the studied cases, enhanced spin qubit lifetime is revealed, reaching almost six orders of magnitude increase for the equilateral triangle gating.
关键词： spin qubit,GaAs,spin relaxation rate,Rabi frequency,quantum dot,gating potential
更新于2025-09-19 17:13:59
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[IEEE 2019 Photonics North (PN) - Quebec City, QC, Canada (2019.5.21-2019.5.23)] 2019 Photonics North (PN) - Sapphire fiber Bragg grating coupled with graded-index fiber lens
摘要： This paper presents the results of three control strategies of managed energy services with home energy management system (HEMS)-integrated devices. The HEMS controls and monitors three types of managed devices: 1) heating; 2) task-speci?c; and 3) energy storage devices. Three approaches are proposed for the rolling optimization by the HEMS, namely, mixed integer linear programming (MILP), continuous relaxation (CR), and fuzzy logic controller (FLC). The CR approach is identi?ed to reduce the computational complexity of the MILP by changing the MILP into an LP solution. Three types of FLC control approaches are proposed, namely, heat-related FLC, task-related FLC, and FLC for the battery. Each control strategy is evaluated against cost optimization, computational resource, and practical implementation. The ?ndings in this paper show that all three algorithmic control strategies successfully perform cost optimization, even with inaccurate forecasting information.
关键词： mixed integer linear programming (MILP),fuzzy logic control (FLC),Continuous relaxation (CR),residential appliance,home energy management system (HEMS)
更新于2025-09-19 17:13:59
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Doppler-shifted laser self-mixing interferometry for enhanced detection sensitivity
摘要： Laser self-mixing interferometry (SMI) is a well-known measurement technique having been applied to the fields of geometrical quantities detection, medical treatment and industry manufacturing. Its detection sensitivity can be improved by frequency shifting towards the laser’s relaxation oscillation frequency (ROF), which has always been implemented by a pair of acousto-optic modulators (AOM). This manuscript presents a novel method based on Doppler effect for frequency shifting, which is based on a rotating disk and has the advantages of convenient adjustment and low cost. The theoretical analysis in the form of Doppler shift and time-delayed rate equations is followed, and simulative and experimental results are included to prove its validity. To our knowledge, this technique has not been used in practice till now, and the proposed structure, with these advantages, can find significant applications in designing high performance SMI sensors, and can extend SMI measurement to more kinds of non-cooperative surfaces.
关键词： Self-mixing interferometry,signal to noise ratio,Doppler shift,sensitivity,relaxation oscillation frequency
更新于2025-09-19 17:13:59
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Size effect on optical performance of blue light-emitting diodes
摘要： In this paper, size effects on optical performance of blue light-emitting diodes (LEDs) are investigated. The essential physical mechanism is studied by fabricating LEDs with various sizes of the active area and testing optical characteristics. It is found that micro-LEDs have better light extracting efficiency and thermal dissipation compared with broad-area LEDs, which is likely due to the small ratio of perimeter and active area. Furthermore, micro-LEDs are more beneficial for displays due to the stable wavelength under the low pulse width modulation (PWM) current density.
关键词： size dependence,micro-LED,strain relaxation,light extract efficiency
更新于2025-09-19 17:13:59
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The formation of intermediate layers in covered Ge/Si heterostructures with low-temperature quantum dots: a study using high-resolution transmission electron microscopy and Raman spectroscopy
摘要： The method of software analysis of high-resolution TEM images using the peak pairs algorithm in combination with Raman spectroscopy was employed to study lattice deformations in Ge/Si(001) structures with low-temperature Ge quantum dots. It was found that the stresses do not spread in a thick Si layer above quantum dots, but completely relax via the formation of a thin boundary layer of mixed composition. However, intermixing of Ge and Si is absent beneath the Ge layer in samples with a Ge coverage of 10 ?A. Besides intermixing was not observed at all, both beneath and above the Ge layer, in samples with a Ge coverage of 6 ?A or less. This may be due to the predominance of Ge di?usion into the Si matrix from the {105} facets of Ge huts, not from the Ge wetting layer, at low temperatures of the Ge/Si structure deposition. The critical thickness of Si coverage at which the intense stress-induced di?usion takes place is determined to lie in the range from 5 to 8 nm.
关键词： lattice strain,Ge/Si quantum dots,peak-pairs analysis,HR TEM,Raman scattering,strain relaxation
更新于2025-09-19 17:13:59
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Magnetic field effect on the slow relaxation of photoconductance in tunnel coupled quantum dot arrays
摘要： The effect of magnetic field on the long-term photoconductance relaxation in two-dimensional arrays of Ge tunnel-coupled quantum dots grown on Si by molecular-beam epitaxy is studied. It was shown that the relaxation process can be slowed down as well as accelerated by magnetic field. The sign of changing the relaxation rate depends on the localization radius and the quantum dot occupancy. To explain an unusual acceleration effect we proposed a model based on the difference in probabilities of carrier transitions to single- or double-occupied quantum dots due to Zeeman effect.
关键词： Quantum dots,Photoconductance relaxation,Magnetic field,Zeeman effect
更新于2025-09-19 17:13:59
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Evidence for Self-healing Benign Grain Boundaries and a Highly Defective Sb <sub/>2</sub> Se <sub/>3</sub> a??CdS Interfacial Layer in Sb <sub/>2</sub> Se <sub/>3</sub> Thin-Film Photovoltaics
摘要： The crystal structure of Sb2Se3 gives rise to unique properties that cannot otherwise be achieved with conventional thin-film photovoltaic materials, such as CdTe or Cu(In,Ga)Se2. It has previously been asserted that, grain boundaries can be made benign provided only the weak van der Waals forces between the (Sb4Se6)n ribbons are disrupted. Here it is shown that non-radiative recombination is suppressed even for grain boundaries cutting across the (Sb4Se6)n ribbons. This is due to a remarkable self-healing process whereby atoms at the grain boundary can relax to remove any electronic defect states within the band gap. Grain boundaries can however impede charge transport due to the fact that carriers have a higher mobility along the (Sb4Se6)n ribbons. Because of the ribbon misorientation certain grain boundaries can effectively block charge collection. Furthermore, it is shown that CdS is not a suitable emitter to partner Sb2Se3 due to Sb and Se inter-diffusion. As a result a highly defective Sb2Se3 interfacial layer is formed that potentially reduces device efficiency through interface recombination.
关键词： Sb2Se3-CdS interface,grain boundary relaxation,grain texture,Kirkendall voids,Sb2Se3 photovoltaics
更新于2025-09-19 17:13:59
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Influence of bromide content on iodide migration in inverted MAPb(I <sub/>1?x</sub> Br <sub/>x</sub> ) <sub/>3</sub> perovskite solar cells
摘要： The effect of a systematic increase in the bromide content on mixed anion methyl ammonium lead halide, MAPb(I1?xBrx)3, perovskite solar cells is investigated. We show that at a critical bromide concentration (7.5%) we supress the slow impedance response from the cells. We link the changing impedance spectrum to a large increase in the activation energy for iodide motion. These results are corroborated by muon spin relaxation measurements, where we show that at the concentration of bromide typically used in high performance perovskite solar cells (17%) there is no sign of iodide motion in powders. Finally, we show JV curve hysteresis as a function of bromide content. The scan rate at which the maximum hysteresis index is observed does not change as the % Br is increased, leading us to conclude that the low frequency impedance response and the JV curve hysteresis are not caused by the same mobile ions.
关键词： bromide content,muon spin relaxation,perovskite solar cells,hysteresis,iodide migration,impedance spectroscopy
更新于2025-09-16 10:30:52
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Accounting for the Dependence of Coil Sensitivity on Sample Thickness and Lift-Off in Inductively Coupled Photoconductance Measurements
摘要： This paper presents the results of three control strategies of managed energy services with home energy management system (HEMS)-integrated devices. The HEMS controls and monitors three types of managed devices: 1) heating; 2) task-speci?c; and 3) energy storage devices. Three approaches are proposed for the rolling optimization by the HEMS, namely, mixed integer linear programming (MILP), continuous relaxation (CR), and fuzzy logic controller (FLC). The CR approach is identi?ed to reduce the computational complexity of the MILP by changing the MILP into an LP solution. Three types of FLC control approaches are proposed, namely, heat-related FLC, task-related FLC, and FLC for the battery. Each control strategy is evaluated against cost optimization, computational resource, and practical implementation. The ?ndings in this paper show that all three algorithmic control strategies successfully perform cost optimization, even with inaccurate forecasting information.
关键词： fuzzy logic control (FLC),home energy management system (HEMS),mixed integer linear programming (MILP),Continuous relaxation (CR),residential appliance
更新于2025-09-16 10:30:52
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Nonlinear optics at excited states of exciton polaritons in two-dimensional atomic crystals
摘要： Exciton polaritons (EP) are partial-light partial-matter quasiparticles in semiconductors demonstrating striking quantum phenomena such as Bose-Einstein condensation and single-photon nonlinearity. In these phenomena, the governing process is the EP relaxation into the ground states upon excitation, where various mechanisms are extensively investigated with thermodynamic limits. However, the relaxation process becomes drastically different and could significantly advance the understanding of EP dynamics for these quantum phenomena, when excited states of EP are involved. Here, for the first time, we observe nonlinear optical responses at the EP excited states in a monolayer tungsten disulphide (WS2) microcavity, including dark excited states and dynamically metastable upper polariton band. The nonlinear optics leads to unique emissions of ground states with prominent valley degree of freedom (DOF) via anomalous relaxation process, which is applicable to a wide range of semiconductors from monolayer transition metal dichalcogenides (TMDs) to emerging halide perovskites. This work promises possible approaches to challenging experiments such as valley polariton condensation. Moreover, it also constructs a valley-dependent solid state three-level system for terahertz photonics and stimulated Raman adiabatic passage.
关键词： excited states,exciton-polaritons,relaxation dynamics,Nonlinear optics,monolayer transition metal dichalcogenide
更新于2025-09-16 10:30:52