Quantum interference effects in a multidriven transition Fg=3←→Fe=2

We have theoretically and experimentally studied the quantum coherence effects of a degenerate transition Fg =3←→Fe=2 system interacting with a weak linearly polarized （with σ＋ components） probe light and a strong linearly polarized （with σ＋ components） coupling field. Due to the competition between the drive Rabi frequency and the Zeeman splitting, electromagnetically induced transparency （EIT） and electromagnetically induced absorption （EIA） are present at the different values of applied magnetic field in the case where the Zeeman splitting of excited state Δe is larger than the Zeeman splitting of ground state Δg （i.e.Δe 〉 Δg）.     

Absorption and Recurrence Spectra of Sodium Rydberg Atom in a Strong External Magnetic Field

Using core-scattered closed-orbit theory, we calculate the photoabsorption and the scaled recurrence spectra of sodium Rydberg atom in strong magnetic fied below ionization threshoM. The non-Coulombic nature of the ionic core have been modified by a model potential, which includes an attractive Coulomb potential and a short-ranged core potential. A family of core-scattered nonhydrogenic closed orbits have also been discovered. The Fourier transformed spectra of sodium atom have allowed direct comparison between peaks in such plot and the scaled action values of closed orbits. The new peaks in the recurrence spectra of sodium atom have been considered as effects caused by the core scattering of returning waves at the ionic core. The results are compared with those of hydrogen case, which show that the core-scattered effects play an important role in alkali-metal atoms.     

Hofstadter＇s Butterfly and Phase Transition of Checkerboard Superconducting Network in a Magnetic Field

We study the magnetic effect of the checkerboard superconducting wire network. Based on the de Gennes- Alexader theory, we obtain difference equations for superconducting order parameter in the wire network. Through solving these difference equations, we obtain the eigenvalues, linked to the coherence length, as a function of magnetic field. The diagram of eigenvalues shows a fractal structure, being so-called Hofstadter＇s butterfly. We also calculate and discuss the dependence of the transition temperature of the checkerboard superconducting wire network on the applied magnetic field, which is related to up-edge of the Hofstadter＇s butterfly spectrum.     

The Motion of a Nonholonomic Chaplygin Sphere in a Magnetic Field,the Grioli Problem,and the Barnett–London Effect

Doklady Physics - In this paper, we consider the motion of a nonholonomic Chaplygin sphere on a plane in a constant magnetic field under the assumption that the sphere has dielectric and...     

Generalized Rashba Coupling Approximation to a Resonant Spin Hall Effect of the Spin–Orbit Coupling System in a Magnetic Field

We introduce a generalized Rashba coupling approximation to analytically solve confined two-dimensional electron systems with both the Rashba and Dresselhaus spin–orbit couplings in an external magnetic field. A solvable Hamiltonian is obtained by performing a simple change of basis, which has the same form as that with only Rashba coupling. Each Landau state becomes a new displaced-Fock state instead of the original Harmonic oscillator Fock state. Analytical energies are consistent with the numerical ones in a wide range of coupling strength even for a strong Zeeman splitting, exhibiting the validity of the analytical approximation. By using the eigenstates, spin polarization correctly displays a jump at the energy-level crossing point, where the corresponding spin conductance exhibits a pronounced resonant peak. As the component of the Dresselhaus coupling increases,the resonant point shifts to a smaller value of the magnetic field. In contrast to pure Rashba couplings, we find that the Dresselhaus coupling and Zeeman splittings tend to suppress the resonant spin Hall effect. Our method provides an easy-to-implement analytical treatment to two-dimensional electron gas systems with both types of spin–orbit couplings by applying a magnetic field.     

Entropy Anomaly in Langevin–Kramers Dynamics with a Temperature Gradient,Matrix Drag,and Magnetic Field

Journal of Statistical Physics - We investigate entropy production in the small-mass (or overdamped) limit of Langevin–Kramers dynamics. The results generalize previous works to provide a...     

Effect of the Initial Laser Phase on the Interaction Between Relativistic Electron and Ultra－Intense Laser Field in a Strong Uniform Magnetic Field

We investigate the influence of the initial laser phase on the interaction between relativistic electron and ultraintense linear polarized laser field in a strong uniform magnetic field. It is found that the dynamic behaviour of the relativistic electron and the emission spectrum varies dramatically with different initial laser field phases.The effect of changing initial phase is contrary in the two parameter regions divided by the resonance condition.The phase dependence of the electron energy and velocity components are also studied. Some beat structure is found when the initial laser phase is zero and this structure is absent when the initial laser phase is a quarter of a period.     

Stimulated Raman Scattering in a Weakly Polar Ⅲ-Ⅴ Semiconductor： Effect of dc Magnetic Field and Free Carrier Concentration

Using the hydrodynamic model of semiconductor plasmas, we perform an analytical investigation of stimulated Raman scattering （SITS） of an electromagnetic pump wave in a transversely magnetized weakly polar semicon- ductor arising from electron-density perturbations and molecular vibrations of the medium both produced at the longitudinal optical phonon frequency. Assuming that the origin of SItS lies in the third-order susceptibility of the medium, we investigate the growth rate of Stokes mode. The dependence of stimulated Raman gain on the external dc magnetic field strength and free carrier concentration is reported. The possibility of the occurrence of optical phase conjugation via SItS is also studied. The steady-state Raman gain is found to be greatly enhanced by the presence of the strong external dc magnetic field.     

Coherent Hole-burning, Mollow Absorption Effect, and Four-wave Mixing in Cycling Transition Fe=0(←→)Fg=1 Subject to a Magnetic Field

We investigate the quantum coherence effects of a cycling transition Fe=0(←→)Fg=1, which is saturated and probed by the circular polarized fields, and is subject to a linearly polarized field and a magnetic field.Saturation field is applied in the case of the maximum coherence between the drive Rabi frequency and magnetic field, corresponding to the electromagnetically induced absorption (EIA) with negative dispersion found by Gu et al.In a small saturation Rabi frequency, the holes are burned in two Autler-Towns peaks outside two symmetric electromagnetically induced transparency (EIT) windows due to the two-photon resonance.When the saturation Rabi frequency is comparable with the drive Rabi frequency, the holes caused by the coherent population oscillation appear in the EIA spectrum.Continuing to increase the saturation Rabi frequency, we observe several emission peaks due to the Mollow absorption effects.Simultaneously, four-wave mixing (FWM) effects in this process are discussed.In the picture of dressed states, we explain the multi-peaks of quantum efficiency of FWM in terms of the multi-photon resonance conditions.We also find a good agreement between the absorption peaks and the FMW peaks.Finally, whenever EIA, EIT, or Mollow absorption happens, the dispersion at the pump-probe detuning center is kept to be negative with increasing the saturation Rabi frequency.It means that this point is suitable to perform the superluminal light propagation experiments.     

基于光子晶体光纤四波混频效应的波长转换研究

研究了光子晶体光纤中的四波混频效应及其波长转换.采用长度为25 m的高非线性色散平坦光子晶体光纤,当泵浦功率为19.8 dBm时,得到100 nm的转换带宽和-20 dB的最大转换效率.实验结果表明,当信号功率低于四波混频阈值时,两路不同波长的信号同时输入产生的四波混频效应互不影响.     

极化子效应对ZnS/CdSe柱型核壳量子点简并四波混频过程的影响

理论计算了带有极化子效应的ZnS/CdSe柱型核壳结构量子点简并四波混频的三阶极化率.在有效质量近似下,采用无限深势阱模型,导出了带有极化子效应的柱型量子点的三阶非线性光学极化率的解析表达式,解三维薛定谔方程得到电子的本征能量和波函数.分析了电子-LO声子和电子-IO声子相互作用对ZnS/CdSe核壳结构量子点简并四波混频的三阶极化率的影响.结果表明,当量子点尺寸一定时,带有极化子效应的χ(3)DFWM比没有极化子时的三阶极化率提高了近3个数量级,并且电子-LO声子的影响比电子-IO声子的影响大得多;当固定核壳量子点的阱宽而内外半径发生变化时,χ(3)DFWM的峰值随之变化,而且极化子效应影响的大小也随之发生变化.     

Electronic Structure and Visible-Light Absorption of Transition Metals(TM=Cr,Mn, Fe,Co) and Zn-Codoped SrTiO_3: a First-Principles Study

First-principles calculations are performed on the influence of transition metal(TM=Cr, Mn, Fe, Co) as codopants on the electronic structure and visible-light absorption of Zn-doped Sr TiO_3. The calculated results show that(Zn,Mn)-codoped Sr TiO_3 requires the smallest formation energy in four codoping systems. The structures of the codoped systems display obvious lattice distortion, inducing a phase transition from cubic to rhombohedral after codoping. Some impurity Cr, Mn and Co 3d states appear below the bottom of conduction band and some Fe 3d states are located above the top of valence band, which leads to a significant narrowing of band gap after transition metal codoping. The enhancement of visible-light absorption are observed in transition metals(TM=Cr, Mn, Fe, Co) and Zn codoped Sr TiO_3 systems. The prediction calculations suggested that the(Zn,Mn)-and(Zn,Co)-codoped SrTiO_3 could be the desirable visible-light photocatalysts.     

Coherent Structures in Transition of a Flat-Plate Boundary Layer at Ma = 0.7

Direct numerical simulation （DNS） of a spatially evolving fiat-plate boundary layer transition process at free stream Mach number 0. 7 is performed. Tollmien-Schlichting （T-S） waves are added on the inlet boundary as the disturbances before transition. Typical coherent structures in the transition process are investigated based on the second invariant of velocity gradient tensor. The instantaneous shear stress and the mean velocity profile in the transition region are studied. In our view, the fact that the peak value of shear stress in the stress concentration area increases and exceeds a threshold value during the later stage of the trallsition process plays an important role in the laminar breakdown process.     

Performance of All-optical WDM Network in Presence of Four-wave Mixing, Optical Amplifier Noise, and Wavelength Converter Noise

The article investigates the effect of four-wave mixing (FWM), amplified spontaneous emission (ASE) noise, and wavelength converter noise on the performance of WDM all-optical networks. Analysis for the evaluation of probability of error has been carried out (a) when only thermal and shot noise are present; (b) when thermal, shot, FWM, and ASE noise are present; and (c) when thermal, shot, FWM, ASE, and wavelength converter noise are present. Numerical results are presented in the graphical forms for the practical values of parameters.     

On the Mixing of K0-K0,D0-D0 and B0-B0

Systematically, we study the long-range contribution to the mixing effects based on the potential model while the QCD correction in Hamiltonian being taken into account. We have found that the long-distance effects are important to K⁰-K⁰ and D⁰-D⁰, but B⁰-B⁰. The QCD correction causes a change to the results, enhances the mixing, for K⁰-K⁰, by a factor of 1.3, whereas for D⁰-D⁰ it is a suppression of about 0.7. The absorptive parts which give rise to ΔΓ have also been discussed and the diquark-intermediate-state contributions to D and B systems are included.     

A Novel Method for Wavelength Conversion with Dual-pump Four-wave Mixing in a Semiconductor Optical Amplifier

Using a semiconductor-fiber ring laser, a novel method for the all optical wavelength conversion based on dual-pump four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) is demonstrated. For the input signal with different wavelengths, only one external pump is needed. This scheme can simplify the dual-pump FWM in SOA and has nearly constant conversion efficiency and signal-to-noise ratio (SNR) over 50nm range of wavelength shifts.     

Energetics, structural and magnetic ordering of H/Fe/M(0 0 1), (M=Cu, Ag) systems

We performed density functional theory calculations using the full-potential linearized augmented plane wave method and generalized gradient approximation to investigate the interaction of hydrogen with Fe surface layers in the Fe/M(0 0 1) system, where M=Cu, Ag. The adsorption of hydrogen is found to be preferable at bridge sites in both H/Fe(0 0 1) and H/Fe/Ag(0 0 1), whereas the preferred sites are the fourfold site above the surface layer in the H/Fe/Cu(0 0 1) system. The adsorption energies are enhanced due to Cu and Ag substrates as compared to Fe(0 0 1) substrates. The local density of states at the Fermi level and the magnetic moments are reduced due to the presence of H for the different systems.