Quantum Interference Effects in p-Si1−x Ge x Quantum Wells

Quantum interference effects, such as weak localization and electron-electron interaction (EEI), have been investigated in magnetic fields up to 11 T for hole gases in a set of Si_1?x Ge _x quantum wells with 0.13<x<0.95. The temperature dependence of the hole phase relaxation time has been extracted from the magneto-resistance between 35 mK and 10 K. The spin-orbit effects that can be described within the Rashba model were observed in low magnetic fields. A quadratic negative magneto-resistance was observed in strong magnetic fields, due to the EEI effect. The hole-phonon scattering time was determined from hole overheating in a strong magnetic field.     

Effect of Charge State in Nearby Quantum Dots on Quantum Hall Systems

Transport properties have been measured on two-dimensional electron system (2DES) with a nearby InAs self-assembled quantum dot layer, in order to clarify the anomalous behavior of magnetoresistance, ρ _xx , and Hall resistance, ρ _xy at $\nu=\frac{1}{3}$ , which was an unsolved problem in our previous paper (Takehana et al.: J. Phys. Soc. Jpn. 75, 114713, 2006). The significant suppression of both ρ _xx and ρ _xy was found to be reduced in the vicinity of $\nu=\frac{1}{3}$ , which indicates that the fractional quantum Hall effect prevent the spin-flip process between localized electrons and that extended 2DES, according to the discussion of the previous paper.     

Spin-Singlet–Spin-Triplet Transitions in Quantum Dots

We calculate the rate of the spin-singlet–spin-triplet (ST) relaxation in the two-electron droplet in a magnetic field. Far from the ST crossing point the rate turns out to be rather significant. In connection with the source-drain transport experiments, we consider this result is an explanation of the observed disappearance of the singlet (upper) level at magnetic fields, which are stronger than the ST crossing value.     

Quantum PLC在船闸控制中的应用

随着航运业的快速发展,国内航运通道愈来愈多,船闸作为航运控制系统的重要组成部分,其系统中的PLC应用也愈发普遍,船闸PLC系统的关键在于它安全、可靠的逻辑顺序、自动化控制,本文就Quantum PLC在船闸控制系统中的应用原理及软硬件系统的应用表现做简要探讨。     

High Field Magnetoelastic Quantum Oscillations of Palladium

The Fermi surface response to external stress is studied by magnetoelastic quantum oscillations at single Pd crystals. The oscillatory magnetization and the magnetostriction of two crystals were measured by capacitive dilatometry at different low temperatures up to 32 T in static field. The experiment confirms the extremal cross sections of the Fermi surface for the L- and X-pockets. The combination of both methods allows to obtain the uniaxial stress dependence of the Fermi surface (using Shoenberg’s formalism). The procedure yields deformation response values in the range from 10 (TPa)^?1 to 100 (TPa)^?1, for stress along [100] and [111]. The new values for the [111] direction seem to have a stronger temperature dependence compared to other directions.     

Quantum SOE在电站控制系统中的应用研究

稳定与安全运行是保证发电系统性能的重要前提,针对提高电站的安全运行,及时寻找事故原因,通过事件顺序记录(SOE)模块与CPU通信接口采集数据至PLC对数据实时进行控制,其性能直接影响机组和重要辅机事故状态分析的及时性和准确性,运动堆栈或冒泡原理找出引起跳机的原因,通过整体的设计和动画效果的显示,实现现场设备的实时监视和报警功能,对电站实时控制及工业现场监控的进一步研究有着积极的意义。     

High-Temperature Quantum–Classical Transition in Solid Methane

Some experimental studies have reported that physical properties of solid methane exhibit a number of anomalies in the temperature interval between \(0.5 T _\mathrm{tr}\) and \(T _\mathrm{tr}\) (\(T _\mathrm{tr}\) is triple point of methane). This paper contains an attempt of systematization and theoretical interpretation of the observed anomalies.     

Cyclotron Resonance of Free Magnetopolaron in Quantum Well Wires

The cyclotron resonance of magnetopolaron in quantum well wires (QWWs) have been studied withthe use of variational solutions to the effective mass equation. The results show that both the abso-lute value of the electron-phonon interaction energy and the cyclotron resonance frequency de-crease with the increase of the sizes of QWWs, and also that the cyclotron resonance frequency in-creases with the external magnetic field.     

Rashba Effect in IV–VI Semiconductor Quantum Wells

The spin–orbit split quantized states for electrons confined in IV–VI lead-salt asymmetric quantum wells (QWs), grown on both (100) and (111) substrates, are obtained analytically within the envelope function approximation with a k p four-band model for the bulk. Nonparabolicity, anisotropy, and break of valley degeneracy are included. In (111) QWs, it is shown that for the valley along the growth direction the Rashba splitting is like the one in III–V QWs, i.e., isotropic and linear in k (for k 0). For the oblique valleys, contrary to the III–V case, a Rashba effect is obtained that is anisotropic and described by an effective magnetic field with nonzero component along the growth direction. Specific results for PbTe/PbEuTe asymmetric QWs with large Rashba splittings are shown.     

Quantum Interference and Surface States Effects in Bismuth Nanowires

We report the observation of Aharonov-Bohm (AB) oscillations for single Bi nanowires with diameter d< 80 nm. The single nanowire samples with glass coating were prepared by the Ulitovsky technique; they were cylindrical single crystals with (10 $\bar{1}$ 1) orientation along the wire axis. The surface of Bi nanowire supports surface states which give rise to a significant population of charge carriers with high effective mass that form a highly conducting tube around the nanowire. The oscillations of longitudinal magnetoresistance (MR) of Bi nanowires with two periods ΔB ₁ and ΔB ₂ proportional to Φ₀ and Φ₀/2 were observed, where Φ₀=h/e is the flux quantum. From B～ 8 T down to B = 0 the extremums of Φ₀/2 oscillations are shifted up to 3π at B = 0 which is the manifestation of Berry phase shift due to electron moving in a nonuniform magnetic field. A derivative of MR was measured at various inclined angles. The observed angle variation of the periods is not in agreement with the theoretical dependence Δ(α)=Δ(0)/cos?α of the size effect oscillations of the “flux quantization” type. Moreover, the equidistant oscillations of MR exist in transverse magnetic fields under certain rotation angles. An interpretation of the MR oscillations is presented.     

Giant Zeeman Splitting of Excitons in a III–V Nonmagnetic Quantum Well Electronically Coupled With a II–VI Semimagnetic Quantum Well

We report on design, fabrication by molecular beam epitaxy, and photoluminescence (PL) studies of GaAs/AlGaAs/ZnSe/ZnCdMnSe double quantum wells (QWs), where resonant electronic coupling occurs through a heterovalent interface. The resonant conditions achieved in the properly designed sample facilitate penetration of the electron wave function from the nonmagnetic GaAs QW into the diluted magnetic semiconductor ZnCdMnSe QW. It results in the sign reversal and drastic increase of a GaAs QW excitonic g factor. The exciton spin splitting observed in the magneto-PL spectra is in general agreement with the calculation performed within the envelope function approximation, taking into account both the inter-well electron coupling and Brillouin-like paramagnetic behavior of the Mn²⁺ ions.     

Ferromagnetic Properties of Mn-Doped III–V Semiconductor Quantum Wells

We investigate magnetic properties of In_1–xMn_xP and Ga_1–xMn_xN quantum wells in the mean-field approximation and show the difference between them. In the case of the In_1–xMn_xP, the dependence of the Curie temperature (T_c) on the hole density exhibits a step-like behavior, reflecting the effect of a two-dimensional Fermi (hole) gas, when the hole–hole exchange interaction is ignored. When we take into account the hole–hole exchange interaction, however, this behavior is broken by the appearance of peaks at the specific two-dimensional carrier densities, and T_c is substantially enhanced in this region. In the case of Ga_1–xMn_xN, the step-like behavior is obscure, and it appears that T_c increases rather continuously with the increasing two-dimensional (2D) carrier density. This shows very weak step-like behavior compared to other III-Mn-V DMS quantum wells, because the hole effective mass of Ga_1–xMn_xN is very large, and the large hole effective mass reduces the energy splitting due to the confinement effect. In a multi-heavy-valence-subband model, the Curie temperature of the In_1–xMn_xP quantum well is about 68 K with 6.5×10¹² holes per cm² and the Mn mole fraction x = 0.05 and the exchange constant J_pd = 0.15 eV nm³. The Curie temperature of the p-type Ga_1–xMn_xN quantum well can be above room temperature, unless the spin-exchange interaction integral is abnormally small.     

Quantum choreography: making molecules dance to technology's tune?

We consider how the ability to control quantum effects might give rise to entirely new technologies, present an overview of potential applications and consider some of the key challenges facing quantum control. A general overview of the main techniques that have been employed successfully so far in controlling various quantum phenomena is given and their applications, advantages and shortcomings are discussed. We conclude with an outlook on the future challenges to be overcome to make quantum technologies a reality.     

Possibility of Inverse Energy Cascade in Two-Dimensional Quantum Turbulence

We numerically study two-dimensional quantum turbulence by using the Gross-Pitaevskii model and the Vortex-Point model. Two-dimensional classical turbulence has long been investigated as an ideal system of geophysical phenomena. The amazing character of this turbulence is inverse energy cascade which carries energy toward low wavenumbers and excites large-scale motion. We expect these phenomena in two-dimensional quantum turbulence because in three-dimensional turbulence we know classical and quantum analogue. However, we have not yet confirmed inverse cascade in two-dimensional quantum turbulence. In this work, we show numerical results and discuss why inverse cascade does not occur in two-dimensional quantum turbulence by referring to the mechanism of two-dimensional classical turbulence.     

Quantum Oscillations and π-States in Multiply Connected Ferromagnet-Superconductor Hybrids

On the basis of Usadel equations, we consider superconductivity nucleation and Josephson current in multiply connected mesoscopic superconductor/ferromagnet (S/F) hybrids. We demonstrate that the exchange field can provoke an increase in the critical temperature T _c of the superconducting transition in the magnetic field. We study the Josephson effect in S/F composites and demonstrate that the negative sign of the critical current (π state) can be realized in such structures despite a dispersion of the distances between different segments of superconducting electrodes.     

Quantum PLC在西气东输天然气站控系统中的应用

本文阐述了西气东输工程无锡-张家港天然气管线站控系统的主要特点和设计需求,基于PLC的站控系统的硬件组成和软件控制的设计方法,PLC双机热备系统的实现及在天然气站控系统中的应用,介绍了关键功能的控制流程和实现方法。     

Theoretical Study of Quantum Gel Formation in?Superfluid 4He

Bosonic density functional theory calculations were carried out for neon, argon, and fluorine based systems in superfluid ⁴He with an emphasis on the formation of dimeric species in the liquid. These atomic species display relatively strong binding with helium and hence their solvation structures in the liquid exhibit highly localized liquid helium layers around them. These solvent layers modify the gas phase dimer potentials by inclusion of a recombination barrier, which provides stabilization for the solvated atoms. Of closed shell species neon is shown to exhibit a recombination barrier of 3 K for the dimer and up to 5.8 K for specific cluster geometries. For argon, the liquid induced potential barrier is only 0.7 K and it has a rather large amount of excess energy available along the recombination coordinate indicating that it is not possible to stabilize argon atoms in superfluid helium. Atomic fluorine shows the most pronounced effect with the recombination barrier of 26.8 K for producing ground state F₂. It is concluded that neon and fluorine atoms are good candidates to form impurity based quantum gels in bulk superfluid helium.     

Very Large Rashba Spin–Orbit Splitting in HgTe Quantum Wells

A large Rashba spin splitting has been observed in the first conduction subband of n-type modulation doped HgTe quantum wells with an inverted band structure via an investigation of Shubnikov–de Haas oscillations as a function of gate voltage. Self-consistent Hartree calculations of the band structure based on an 8 × 8 k p model quantitatively describe the experimental results. It has been shown that the heavy-hole nature of the H1 conduction subband greatly influences the spatial distribution of electrons in the quantum well and also enhances the Rashba spin splitting at large electron densities. These are unique features of type III heterostructures in the inverted band regime. The k ³ dispersion predicted by an analytical model is a good approximation of the self-consistent Hartree calculations for small values of the in-plane wave vector k . This is in contrast to the commonly used k dispersion for the conduction subband in type I heterojunctions.