Improved reproducing kernel particle method for piezoelectric materials
Finite-time robust control of uncertain fractional-order Hopfield neural networks via sliding mode control
A novel stable value iteration-based approximate dynamic programming algorithm for discrete-time nonlinear systems
Quantum Monte Carlo study of hard-core bosons in Creutz ladder with zero flux
Solution of the spin-one DKP oscillator under an external magnetic field in noncommutative space with minimal length
Non-Markovian speedup dynamics control of the damped Jaynes-Cummings model with detuning
Quantum speed limit time of a two-level atom under different quantum feedback control
We investigate the quantum speed limit time (QSLT) of a two-level atom under quantum-jump-based feedback control or homodyne-based feedback control. Our results show that the two different feedback control schemes have different influences on the evolutionary speed. By adjusting the feedback parameters, the quantum-jump-based feedback control can induce speedup of the atomic evolution from an excited state, but the homodyne-based feedback control cannot change the evolutionary speed. Additionally, the QSLT for the whole dynamical process is explored. Under the quantum-jump-based feedback control, the QSLT displays oscillatory behaviors, which implies multiple speed-up and speed-down processes during the evolution. While, the homodyne-based feedback control can accelerate the speed-up process and improve the uniform speed in the uniform evolution process.
Quantum coherence and non-Markovianity of an atom in a dissipative cavity under weak measurement
Improved quantum randomness amplification with finite number of untrusted devices based on a novel extractor
Novel quantum watermarking algorithm based on improved least significant qubit modification for quantum audio
Soliton excitations in a polariton condensate with defects
Transitionless driving on local adiabatic quantum search algorithm
Current transport and mass separation for an asymmetric fluctuation system with correlated noises
Detection of meso-micro scale surface features based on microcanonical multifractal formalism
Topological horseshoe analysis and field-programmable gate array implementation of a fractional-order four-wing chaotic attractor
Controllable optical superregular breathers in the femtosecond regime
Leader-following consensus of discrete-time fractional-order multi-agent systems
Spin polarization and dispersion effects in emergence of roaming transition state for nitrobenzene isomerization
Direct observation of melted Mott state evidenced from Raman scattering in 1T-TaS2 single crystal Hot!
The evolution of electron correlation and charge density wave (CDW) in 1T-TaS2 single crystal has been investigated by temperature-dependent Raman scattering, which undergoes two obvious peaks of A1g modes about 70.8 cm-1 and 78.7 cm-1 at 80 K, respectively. The former peak at 70.8 cm-1 is accordant with the lower Hubbard band, resulting in the electron-correlation-driven Mott transition. Strikingly, the latter peak at 78.7 cm-1 shifts toward low energy with increasing the temperature, demonstrating the occurrence of nearly commensurate CDW phase (melted Mott phase). In this case, phonon transmission could be strongly coupled to commensurate CDW lattice via Coulomb interaction, which likely induces appearance of hexagonal domains suspended in an interdomain phase, composing the melted Mott phase characterized by a shallow electron pocket. Combining electronic structure, atomic structure, transport properties with Raman scattering, these findings provide a novel dimension in understanding the relationship between electronic correlation, charge order, and phonon dynamics.
Measurement of the bulk and surface bands in Dirac line-node semimetal ZrSiS Hot!
Dirac semimetals are materials in which the conduction and the valence bands have robust crossing points protected by topology or symmetry. Recently, a new type of Dirac semimetals, so called the Dirac line-node semimetals (DLNSs), have attracted a lot of attention, as they host robust Dirac points along the one-dimensional (1D) lines in the Brillouin zone (BZ). In this work, using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations, we systematically investigated the electronic structures of non-symmorphic ZrSiS crystal where we clearly distinguished the surface states from the bulk states. The photon-energy-dependent measurements further prove the existence of Dirac line node along the X-R direction. Remarkably, by in situ surface potassium doping, we clearly observed the different evolutions of the bulk and surface electronic states while proving the robustness of the Dirac line node. Our studies not only reveal the complete electronic structures of ZrSiS, but also demonstrate the method manipulating the electronic structure of the compound.
Two-dimensional transport and strong spin-orbit interaction in SrMnSb2 Hot!
Optical study on intermediate-valence compounds Yb1-xLuxAl3 Hot!
We report an optical spectroscopy study on intermediate valence system Yb1-xLuxAl3 with x=0, 0.25, 0.5, 0.75, and 1. The Kondo temperature in the system is known to increase with increasing Lu concentration. Therefore, it is expected that the energy scale of the hybridization gap should increase with increasing Lu concentration based on the periodic Anderson model. On the contrary, we find that the spectral structure associated with the hybridization effect shifts monotonically to lower energy. Furthermore, the Lu substitution results in a substantial increase of the free carrier spectral weight and less pronounced plasma frequency reduction upon lowering temperature. We attribute the effect to the disruption of the Kondo lattice periodicity by the random substitution of Yb by Lu. The work highlights the importance of the lattice periodicity of the rare earth element for understanding the Kondo lattice phenomena.
A new fully quantum-mechanical method used to calculate the collisional broadening coefficients and shift coefficients of Rb D1 lines perturbed by noble gases He and Ar
Simulating resonance-mediated two-photon absorption enhancement in rare-earth ions by a rectangle phase modulation
Photoelectron longitudinal momentum distributions containing nondipole effects
Attosecond transient absorption spectroscopy: Comparative study based on three-level modeling
Plasma-screening effects on positronium formation
Plasma-screening effects on positronium (Ps) formation for positron-hydrogen collisions in a Debye plasma environment is further investigated using the screening approximation model with the inclusion of the modified structure of Ps. More accurate Ps formation cross sections (n=1, 2) are obtained for various Debye lengths from the Ps formation thresholds to 50 eV. The influence of considering modified bound-state wave functions and eigenenergies for the Ps is found to result in the reduction of the Ps formation cross sections at low energies, whereas it cannot counteract the enhancement of the Ps formation by the Debye screening.
Comparison of the sensitivities for atom interferometers in two different operation methods
We investigated the sensitivities of atom interferometers in the usual fringe-scanning method (FSM) versus the fringe-locking method (FLM). The theoretical analysis shows that for typical noises in atom interferometers, the FSM will degrade the sensitivity while the FLM does not. The sensitivity-improvement factor of the FLM over the FSM depends on the type of noises, which is validated by numerical simulations. The detailed quantitative analysis on this fundamental issue is presented, and our analysis is readily extendable to other kinds of noises as well as other fringe shapes in addition to a cosine one.
A broadband cross-polarization conversion anisotropic metasurface based on multiple plasmon resonances
Birefringence via Doppler broadening and prevention of information hacking
Aberration correction of conformal dome based on rotated cylindrical lenses for ultra-wide field of regard
A new compact conformal dome optical system was designed, and the aberration characteristics of the dome were investigated using Zernike aberration theory. The aberrations induced by the conformal dome at different fields of regard (FORs) from 0^o to 90^o were effectively balanced by a pair of rotating cylindrical lenses. A design method was introduced and the optimization results were analyzed in detail. The results showed that the Zernike aberrations produced by the conformal dome were decreased dramatically. Also, a complete conformal optical system was designed to further illustrate the aberration correction effect of the rotating cylindrical lenses. Using a pair of rotating cylindrical lenses not only provided an ultra-wide FOR, but also perduced a better image quality of the optical system.
Super-sensitive phase estimation with coherent boosted light using parity measurements
We consider a passive and active hybrid interferometer for phase estimation, which can reach the sub-shot-noise limit in phase sensitivity with only the cheapest coherent sources. This scheme is formed by adding an optical parametric amplifier before a Mach-Zehnder interferometer. It is shown that our hybrid protocol can obtain a better quantum Cramer-Rao bound than the pure active (e.g., SU(1,1)) interferometer, and this precision can be reached by implementing the parity measurements. Furthermore, we also draw a detailed comparison between our scheme and the scheme suggested by Caves[Phys. Rev. D 23 1693 (1981)], and it is found that the optimal phase sensitivity gain obtained in our scheme is always larger than that in Caves' scheme.
Broad bandwidth interference filter-stabilized external cavity diode laser with narrow linewidth below 100 kHz
Design of photonic crystal fiber with elliptical air-holes to achieve simultaneous high birefringence and nonlinearity
Temperature rise induced by an annular focused transducer with a wide aperture angle in multi-layer tissue
Acoustic radiation force induced by two Airy-Gaussian beams on a cylindrical particle
Envelope solitary waves and their reflection and transmission due to impurities in a granular material
Comment on “Band gaps structure and semi-Dirac point of two-dimensional function photonic crystals” by Si-Qi Zhang et al.
Excitation of chorus-like waves by temperature anisotropy in dipole research experiment (DREX): A numerical study
Due to their significant roles in the radiation belts dynamics, chorus waves are widely investigated in observations, experiments, and simulations. In this paper, numerical studies for the generation of chorus-like waves in a launching device, dipole research experiment (DREX), are carried out by a hybrid code. The DREX plasma is generated by electron cyclotron resonance (ECR), which leads to an intrinsic temperature anisotropy of energetic electrons. Thus the whistler instability can be excited in the device. We then investigate the effects of three parameters, i.e., the cold plasma density nc, the hot plasma density nh, and the parallel thermal velocity of energetic electrons, on the generation of chorus-like waves under the DREX design parameters. It is obtained that a larger temperature anisotropy is needed to excite chorus-like waves with a high nc with other parameters fixed. Then we fix the plasma density and parallel thermal velocity, while varying the hot plasma density. It is found that with the increase of nh, the spectrum of the generated waves changes from no chorus elements, to that with several chorus elements, and then further to broad-band hiss-like waves. Besides, different structures of chorus-like waves, such as rising-tone and/or falling-tone structures, can be generated at different parallel thermal velocities in the DREX parameter range.
Bandgap engineering to tune the optical properties of BexMg1-xX (X=S, Se, Te) alloys
Synthesized few-layers hexagonal boron nitride nanosheets
Bulk and surface damages in complementary bipolar junction transistors produced by high dose irradiation
Two complementary types NPN and PNP of bipolar junction transistors (BJTs) were exposed to high dose of neutrons and gamma rays. The change in the base and collector currents, minority carriers lifetime, and current gain factor β with respect to the dose were analyzed. The contributions of the base current according to the defect types were also reported. It was declared that the radiation effect of neutrons was almost similar between the two transistor types, this effect at high dose may decrease the value of β to less than one. The Messenger-Spratt equation was used to describe the experimental results in this case. However, the experimental data demonstrated that the effect of gamma rays was generally higher on NPN than PNP transistors. This is mainly attributed to the difference in the behavior of the trapped positive charges in the SiO2 layers. Meanwhile, this difference tends to be small for high gamma dose.
First-principles calculations on elastic, magnetoelastic, and phonon properties of Ni2FeGa magnetic shape memory alloys
The elastic, magnetoelastic, and phonon properties of Ni2 FeGa were investigated through first-principles calculations. The obtained elastic and phonon dispersion curves for the austenite and martensite phases agree well with available theoretical and experimental results. The isotropic elastic moduli are also predicted along with the polycrystalline aggregate properties including the bulk modulus, shear modulus, Young's modulus, and Poisson's ratio. The Pugh ratio indicates that Ni2 FeGa shows ductility, especially the austenite phase, which is consistent with the experimental results. The Debye temperatures of the Ni2 FeGa in the austenite and martensite phases are 344 K and 392 K, respectively. It is predicted that the magnetoelastic coefficient is -5.3×106 J/m3 and magnetostriction coefficient is between 135 and 55 ppm in the Ni2 FeGa austenite phase.
Ejecta from periodic grooved Sn surface under unsupported shocks
Magnetism and piezoelectricity of hexagonal boron nitride with triangular vacancy
First-principle calculations reveal that the configuration system of hexagonal boron nitride (h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer. Interestingly, the h-BN with boron atom vacancy (VB-BN) displays metallic behavior with a total magnetic moment being 0.46μB per cell, while the h-BN with nitrogen atom vacancy (VN-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μB per cell. Remarkably, piezoelectric stress coefficient e11 of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d11 (12.42 pm/V) of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS2 monolayer, which is mainly due to the spin-down electronic state in the VN-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems (NEMS) and nanoscale electronics devices.
Transport properties of mixing conduction in CaF2 nanocrystals under high pressure
Spin-dependent balance equations in spintronics
Two types of ground-state bright solitons in a coupled harmonically trapped pseudo-spin polarization Bose–Einstein condensate
A combined system for generating a uniform magnetic field and its application in the investigation of Efimov physics
Charge distribution in graphene from quantum calculation
The local charge distributions of different shape graphene sheets are investigated by using the quantum calculations. It is found that the charge distribution on carbon atom is not uniform, strongly depending on its position in the graphene and its local atomic environment condition. The symmetrical characteristic and geometrical structures of graphene also have an important influence on the charge distribution. The charges of atom at the graphene edge are strongly related to their surrounding bonds. It is found that the charges of double-bonded atom at the zigzag edge are closely related to the bond angle, but the charges of double-bonded atom at the armchair edge are mainly influenced by the area of triangle. The charges of triple-bonded atom at the edge are mainly affected by the standard deviation of the length of the associated triple bonds.
Density functional theory analysis of electronic structure and optical properties of La-doped Cd2SnO4 transparent conducting oxide
Structural, electronic, and mechanical properties of cubic TiO2: A first-principles study
Electronic and mechanical properties of half-metallic half-Heusler compounds CoCrZ (Z=S, Se, and Te)
Optical interaction between one-dimensional fiber photonic crystal microcavity and gold nanorod
Localized surface plasmon resonance (LSPR) has demonstrated its promising capability for biochemical sensing and surface-enhanced spectroscopy applications. However, harnessing LSPR for remote sensing and spectroscopy applications remains a challenge due to the difficulty in realizing a configuration compatible with the current optical communication system. Here, we propose and theoretically investigate a hybrid plasmonic-photonic device comprised of a single gold nanorod and an optical fiber-based one-dimensional photonic crystal microcavity, which can be integrated with the optical communication system without insertion loss. The line width of the LSPR, as a crucial indicator that determines the performances for various applications, is narrowed by the cavity-plasmon coupling in our device. Our device provides a promising alternative to exploit the LSPR for high-performance remote sensing and spectroscopy applications.
Raman spectrum study of δ -doped GaAs/AlAs multiple-quantum wells
Closed-form internal impedance model and characterization of mixed carbon nanotube bundles for three-dimensional integrated circuits
Electronic states and spin-filter effect in three-dimensional topological insulator Bi2Se3 nanoribbons
We study the electronic band structure, density distribution, and transport of a Bi2Se3 nanoribbon. We find that the density distribution of the surface states is dependent on not only the shape and size of the transverse cross section of the nanoribbon, but also the energy of the electron. We demonstrate that a transverse electric field can eliminate the coupling between surface states on the walls of the nanoribbon, remove the gap of the surface states, and restore the quantum spin Hall effects. In addition, we study the spin-dependent transport property of the surface states transmitting from top and bottom surfaces (x-y plane) to the side surfaces (z-x plane) of a Bi2Se3 nanoribbon. We find that transverse electric fields can open two surface channels for spin-up and -down Dirac electrons, and then switch off one channel for the spin-up Dirac electron. Our results may provide a simple way for the design of a spin filter based on topological insulator nanostructures.
Directional mechanical and thermal properties of single-layer black phosphorus by classical molecular dynamics
High-pressure synchrotron x-ray diffraction and Raman spectroscopic study of plumbogummite
Influences of La and Ce doping on giant magnetocaloric effect of EuTiO
Strong anti-strain capacity of CoFeB/MgO interface on electronic structure and state coupling
Multiferroic and enhanced microwave absorption induced by complex oxide interfaces
A general method for large-scale fabrication of Cu nanoislands/dragonfly wing SERS flexible substrates
Substitution priority of Eu2+ in multi-cation compound Sr0.8Ca0.2Al2Si2O8 and energy transfer
Facilitative effect of graphene quantum dots in MoS2 growth process by chemical vapor deposition
A novel multi-scroll chaotic generator: Analysis, simulation, and implementation
Pressure-induced structural evolution of apatite-type La9.33Si6O26
The pressure-induced structural evolution of apatite-type La9.33Si6O26 was systematically studied using in situ synchrotron x-ray diffraction (XRD). The XRD spectra indicated that a subtly reversible phase transition from P63/m to P63 symmetry occurred at~13.6 GPa because of the tilting of the SiO4 tetrahedra under compression. Furthermore, the La9.33Si6O26 exhibited a higher axial compression ratio for the a-axis than the c-axis, owing to the different axial arrangement of the SiO4 tetrahedra. Interestingly, the high-pressure phase showed compressibility unusually higher than that of the initial phase, suggesting that the low P63 symmetry provided more degrees of freedom. Moreover, the La9.33Si6O26 exhibited a lower phase transition pressure (PT) and a higher lattice compression than La10Si6O27. Comparisons between La9.33Si6O26 and La10Si6O27 provided a deeper understanding of the effect of interstitial oxygen atoms on the structural evolution of apatite-type lanthanum silicates (ATLSs).
Photon-counting chirped amplitude modulation lidar system using superconducting nanowire single-photon detector at 1550-nm wavelength
We demonstrate a photon-counting chirped amplitude modulation (CAM) light detection and ranging (lidar) system incorporating a superconducting nanowire single-photon detector (SNSPD) and operated at a wavelength of 1550 nm. The distance accuracy of the lidar system was determined by the CAM bandwidth and signal-to-noise ratio (SNR) of an intermediate frequency (IF) signal. Owing to a short dead time (10 ns) and negligible dark count rate (70 Hz) of the SNSPD, the obtained IF signal attained an SNR of 42 dB and the direct distance accuracy was improved to 3 mm when the modulation bandwidth of the CAM signal was 240 MHz and the modulation period was 1 ms.
Improved performance of Ge n+/p diode by combining laser annealing and epitaxial Si passivation
Excessive levitation for the efficient loading of large-volume optical dipole traps
We study the excessive levitation effect in the magnetically levitated loading process of ultracold Cs atoms into a large-volume crossed optical dipole trap. We analyze the motion of atoms with a non-zero combined gravito-magnetic force during the loading, where the magnetically levitated force catches up with and surpasses the gravity. We present the theoretical variations of both acceleration and velocity with levitation time and magnetic field gradient. We measure the evolution of the number of trapped atoms with the excessive levitation time at different magnetic field gradients. The dependence of the number of atoms on the magnetic field gradient is also measured for different excessive levitation times. The theoretical analysis shows reasonable agreement with the experimental results. Our investigation illustrates that the excessive levitation can be used to reduce the heating effect of atoms in the magnetically levitated loading process, and to improve the loading rate of a large-volume optical dipole trap.
Efficient design of perovskite solar cell using mixed halide and copper oxide
A compact and high-power silicon-wafer solar strip-cells-array module integrated with an array concentrator
A compact, low-cost and high-output-power silicon-wafer solar strip-cells-array module (SCAM) was experimentally demonstrated. The proposed SCAM consisted mainly of a silicon-wafer strip-cell sparse array and low-concentration-ratio array concentrator based on an epoxy resin polymer (ERP) cylindrical plano-convex lens. A polymer replication process based on a polydimethylsiloxane mold was used to fabricate the ERP lens array concentrator. The results show that 46.94% of the silicon-wafer cell was saved in the designed SCAM. Moreover, the output power of the SCAM with a low concentration ratio of 8 suns was improved by 8.6%, compared with a whole piece of a conventional silicon-wafer solar cell with the same area as the module. The proposed method encapsulating solar cells provides a means to reduce the usage of silicon cells in modules as well as improving the output power of modules.
To what extent of ion neutralization can multivalent ion distributions around RNA-like macroions be described by Poisson-Boltzmann theory?
A network of conformational transitions in an unfolding process of HP-35 revealed by high-temperature MD simulation and a Markov state model
Improved data analysis method of single-molecule experiments based on probability optimization
Interfaces of high-efficiency kesterite Cu2ZnSnS(e)4 thin film solar cells
Cu2ZnSnS(e)4 (CZTS(e)) solar cells have attracted much attention due to the elemental abundance and the non-toxicity. However, the record efficiency of 12.6% for Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is much lower than that of Cu(In,Ga)Se2 (CIGS) solar cells. One crucial reason is the recombination at interfaces. In recent years, large amount investigations have been done to analyze the interfacial problems and improve the interfacial properties via a variety of methods. This paper gives a review of progresses on interfaces of CZTS(e) solar cells, including:(i) the band alignment optimization at buffer/CZTS(e) interface, (ii) tailoring the thickness of MoS(e)2 interfacial layers between CZTS(e) absorber and Mo back contact, (iii) the passivation of rear interface, (iv) the passivation of front interface, and (v) the etching of secondary phases.
Promise of commercialization: Carbon materials for low-cost perovskite solar cells
Perovskite solar cells (PVSCs) have attracted extensive studies due to their high power conversion efficiency (PCE) with low-cost in both raw material and processes. However, there remain obstacles that hinder the way to their commercialization. Among many drawbacks in PVSCs, we note the problems brought by the use of noble metal counter electrodes (CEs) such as gold and silver. The costly Au and Ag need high energy-consumption thermal evaporation process which can be made only with expensive evaporation equipment under vacuum. All the factors elevate the threshold of PVSCs' commercialization. Carbon material, on the other hand, is a readily available electrode candidate for the application as CE in the PVSCs. In this review, endeavors on PVSCs with low-cost carbon materials will be comprehensively discussed based on different device structures and carbon compositions. We believe that the PVSCs with carbon-based CE hold the promise of commercialization of this new technology.
Theoretical study on the kesterite solar cells based on Cu2ZnSn(S,Se)4 and related photovoltaic semiconductors
The kesterite thin film solar cells based on the quaternary Cu2ZnSnS4 and Cu2ZnSnSe4 and their alloys Cu2ZnSn(S,Se)4 have been considered as environment-friendly and non-toxic alternatives to the currently commercialized CdTe and Cu(In,Ga)Se2 thin film solar cells. From the theoretical point of view, we will review how the group I2-Ⅱ-IV-VI4 quaternary compound semiconductors are derived from the binary CdTe and the ternary CuInSe2 or CuGaSe2 through the cation mutation, and how the crystal structure and electronic band structure evolve as the component elements change. The increased structural and chemical freedom in these quaternary semiconductors opens up new possibility for the tailoring of material properties and design of new light-absorber semiconductors. However, the increased freedom also makes the development of high-efficiency solar cells more challenging because much more intrinsic point defects, secondary phases, surfaces, and grain-boundaries can exist in the thin films and influence the photovoltaic performance in a way different from that in the conventional CdTe and Cu(In,Ga)Se2 solar cells. The experimental characterization of the properties of defects, secondary phase, and grain-boundaries is currently not very efficient and direct, especially for these quaternary compounds. First-principles calculations have been successfully used in the past decade for studying these properties. Here we will review the theoretical progress in the study of the mixed-cation and mixed-anion alloys of the group I2-Ⅱ-IV-VI4 semiconductors, defects, alkaline dopants, and grain boundaries, which provided very important information for the optimization of the kesterite solar cell performance.
Recent progress of colloidal quantum dot based solar cells
Colloidal quantum dot (CQD) solar cells have attracted great interest due to their low cost and superior photo-electric properties. Remarkable improvements in cell performances of both quantum dot sensitized solar cells (QDSCs) and PbX (X=S, Se) based CQD solar cells have been achieved in recent years, and the power conversion efficiencies (PCEs) exceeding 12% were reported so far. In this review, we will focus on the recent progress in CQD solar cells. We firstly summarize the advance of CQD sensitizer materials and the strategies for enhancing carrier collection efficiency in QDSCs, including developing multi-component alloyed CQDs and core-shell structured CQDs, as well as various methods to suppress interfacial carrier recombination. Then, we discuss the device architecture development of PbX CQD based solar cells and surface/interface passivation methods to increase light absorption and carrier extraction efficiencies. Finally, a short summary, challenge, and perspective are given.