Single-band Hubbard model with spin-orbit coupling

A single-band Hubbard hamiltonian with spin-orbit coupling included in the hopping integral is solved in terms of the solution with no spin-orbit coupling. For an openended linear chain the spectrum is independent ofu/t=tan θ, whereu(t) measures the spin-orbit (ordinary) contribution to the hopping integral; and for the half-filled band the spin-correlations are spiral-like with turn angle 2θ+π. In the case of a ring ofN sites the spectrum is periodic in θ with period 2π/N; for the half-filled-band case the period is π/N in the zero-band-width limit. Generalizations to higher dimensions are noted.     

Correlation evolution and monogamy of two geometric quantum discords in multipartite systems

We study the controlled photon emission of generic V-type three-level molecules (e.g. BaF) via a radio frequency field. The density matrix approach was employed to calculate the probabilities of emission of one or two X-polarised photons. The influence of the relative delay phase between the sequential pulse on the emission photon probabilities can be enhanced or eliminated by the polarisation of the radio frequency field. For θ ∈ [ 0.35π,0.75π ] + nπ, the influence of the relative delay phase is enhanced, whereas for θ ? [ 0.35π,0.75π ] + nπ the influence is suppressed. The probabilities of emitting one or two X-polarised photons oscillate with the modulation index ζ, and several zero points exist, which could be used as a trigger for photon emissions. The results also demonstrated the phenomenon of radio frequency field-assisted photon absorption.     

Measuring in-plane and out-of-plane coupled motions of microstructures by stroboscopic microscopic interferometry

A stroboscopic Mirau microscopic interferometer system for measuring in-plane and out-of-plane periodic motions of microstructures is demonstrated. One full cycle of a periodic motion is divided into a number of motion phases. One sequence of interferograms with different phase shifting steps is collected at every motion phase by using stroboscopic imaging. A bright-field image can be extracted from one sequence of interferograms with the same motion phase. In-plane displacements are measured by applying an image matching method to all bright-field images, followed by a compensation for the relative positions of interferograms at the different motion phases, before calculating the phase distribution related to out-of-plane deformation. We demonstrate its capability for measuring a combination of out-of-plane deformation and in-plane displacement in a microresonator.     

Dynamics of coupled Josephson junctions under the influence of applied fields

We investigate the effect of the phase difference of applied fields on the dynamics of mutually coupled Josephson junctions. A phase difference between the applied fields desynchronizes the system. It is found that though the amplitudes of the output voltage values are uncorrelated, a phase correlation is found to exist for small values of applied phase difference. The dynamics of the system is found to change from chaotic to periodic for certain values of phase difference. We report that by keeping the value of phase difference as π, the system continues to be in periodic motion for a wide range of values of system parameters. This result may find applications in devices like voltage standards, detectors, SQUIDS, etc., where chaos is least desired.     

Effects of geometry and linearly polarized cavity photons on charge and spin currents in a quantum ring with spin-orbit interactions

We calculate the persistent charge and spin polarization current inside a finite-width quantum ring of realistic geometry as a function of the strength of the Rashba or Dresselhaus spin-orbit interaction. The time evolution in the transient regime of the two-dimensional (2D) quantum ring connected to electrically biased semi-infinite leads is governed by a time-convolutionless non-Markovian generalized master equation. The electrons are correlated via Coulomb interaction. In addition, the ring is embedded in a photon cavity with a single mode of linearly polarized photon field, which is polarized either perpendicular or parallel to the charge transport direction. To analyze carefully the physical effects, we compare to the analytical results of the toy model of a one-dimensional (1D) ring of non-interacting electrons with spin-orbit coupling. We find a pronounced charge current dip associated with many-electron level crossings at the Aharonov-Casher phase ΔΦ = π, which can be disguised by linearly polarized light. Qualitative agreement is found for the spin polarization currents of the 1D and 2D ring. Quantitatively, however, the spin polarization currents are weaker in the more realistic 2D ring, especially for weak spin-orbit interaction, but can be considerably enhanced with the aid of a linearly polarized electromagnetic field. Specific spin polarization current symmetries relating the Dresselhaus spin-orbit interaction case to the Rashba one are found to hold for the 2D ring, which is embedded in the photon cavity.     

Theory of the angular distribution of molecular orbitalK x rays seen in heavy-ion-atom collisions

Dynamical calculations of angular distributions and intensities of two-collision 1s σ molecular orbital x rays in 12–90-MeV Ni + Ni collisions are reported. The Coriolis and spin-orbit coupling between 2pσ and 2pπ and the 3pσ and 3pπ molecular orbitals is included. Due to Coriolis coupling, the molecular wavefunctions and therefore the transition dipoles do not follow the rotation of the internuclear axis in collisions with small impact parameters, but remain approximately fixed in direction. Consequently one can predict the symmetry relations between the laboratoryx, y, andz components of the molecular orbital intensity and therefore the anisotropy of the radiation seen at energies near the united atomK α x-ray line. These relations are used to predict anisotropies of molecular orbital radiation in encounters with large united atom atomic numbers,Z ₁ +Z ₂>137. For Ni + Ni encounters, a lower population of the 2pπ and 3pπ orbitals than the 2pσ and 3pσ orbitals is needed to reproduce the observed anisotropies.     

Line energy,line tension and drop size

The relation between drop radius, r, the force to move the three phase contact line and the advancing and receding contact angles θ_A and θ_R is studied. To keep the line energy (energy per 2πr, also named line tension) independent of r, the modified Young equation predicts that the advancing and receding contact angles, θ_A and θ_R, change considerably with r. As shown by many investigators, θ_A and θ_R change negligibly, if at all, with r. We quantify recent evidences showing that the line energy is a function of the Laplace pressure and show that this way the modified Young equation is correct and still θ_A and θ_R should hardly change with r. According to our model, the small surface deformation associated with the unsatisfied normal component of the Young equation results in higher intermolecular interactions at the three phase contact line which corresponds to a higher retention force. This time increasing effect is supported by recent experiments.     

The research on beat length of polarization maintaining optical fiber with external pressure

Based on the coupled mode equations and elastic optic effect theory, the relationship between polarization maintaining fiber (PMF) beat length and external pressure was analyzed. Moreover, the beat length variation with different external pressure values F as well as angles θ between the pressure direction and PMF's x-axis was calculated numerically. The results demonstrated that the beat length variation was determined both by F and θ simultaneously. When F was a constant, the beat length was changed periodically in π cycle sinusoidal form with θ variation. Then, the minimum and maximum values of beat length would be obtained when θ were even and odd multiples of π/2, respectively. Meanwhile, the beat length variation was linear with F as θ was fixed. In this situation and with F increasing, if θ ∈ (kπ + π/4, kπ + 3π/4) (k ∈ Z), the beat length would increase linearly; otherwise, the beat length variation would be in the opposite direction while θ ∈ (kπ − π/4, kπ + π/4) (k ∈ Z); however, it remained almost unchanged in the case of θ = kπ ± π/4 (k ∈ Z). Finally, the beat length was measured with different pressure values F and angles θ based on a Sagnac interferometer system, and the results shown a great agreement with the theoretical analysis and simulation.     

Diffraction dissociation of neutrons into (pπ−) on protons in the momentum range 35 to 65 GeV/c

The diffraction dissociation reaction n + p → (pπ^?) + p was studied at the Serpukhov accelerator neutron beam in the momentum range 35–65 GeV/c in an electronics experiment. The differential cross sections of the reaction are analysed and presented in the five-dimensional phase space $\text{(p}{}_{\mathrm{<mtext>n</mtext>}}\text{, m}{}^1\text{, t,}\text{cos}\text{θ}{}^1\text{, φ}{}^1\text{)}$. The backward peak observed in the distribution over if cosθin GJ ¹ in the Gottfried-Jackson frame of if(pπ) is interpreted as a baryon-exchange effect. The angular distribution of the (pπ^?) system is compared with Deck-type models.     

Lowest excited states of 2-aminopurine

Absorption and fluorescene spectra and quantum yields of emission over a wide range of pH and solvent polarity were measured for 2-aminopurine and 2-dimethylaminopurine. An increase in dipole moment and a rise of pK values for N₁(N₃) ring atom protonation in the excited state were demonstrated. Thus, the lowest excited singlet state shows partially the (1, a_π¹) configuration. The polarization, lifetimes and the phosphorescence-to-fluorescence ratios indicate that spin-orbit coupling of ¹(n, π¹) and ¹(1, a_π¹) with the lowest triplet state is the main source of phosphorescence intensity. The matrix element of spin-orbit coupling of ¹(n, π¹) to the T₁ state is about 33 times larger than that of ¹(1, a_π¹). The temperature- dependent process of 2-aminopurine fluorescence quenching in either is presumably due to the thermal population of the second excited triplets state of (n, π¹) configuration, which can approximately be located at 370 cm^-1 above the lowest (1, a_π¹) singlet.     

Spin polarization of 29P produced through low energy nuclear reaction

Spin polarization of short-lived β-emitting nucleus ²⁹P (I ^π = 1/2^?+?, T _1/2 = 4.14 s) produced through the ²⁸P(d, n) ²⁹P reaction was studied as functions of the incident deuteron energy E _d and the recoil angle θ of ²⁹P. New optimum condition was found at E _d = 3.3 MeV and θ = 30° where polarization of ²⁹P is ?(4.1 ± 0.7) %.     

Numerical simulation study about spin resonant depolarization due to spin—orbit coupling

Spin polarization phenomenon in lepton circular accelerators had been known for many years. It gives new approach for physicists to study about spin feature of fundamental particles and dynamics of spin-orbit coupling, such as spin resonances. We use numerical simulation to study the feature of spin under the modulation of orbital motion in electron storage ring. The various cases of depolarization due to spin-orbit coupling through emitting photon and misalignment of magnets in the ring are discussed.     

Calculation of transverse and longitudinal space charge effects within the framework of the fully six-dimensional formalism

In the following report we describe a method for calculating the envelope of a particle bunch in linear coupled storage rings and transport systems in the presence of transverse and longitudinal space charge forces using the (canonical) variablesx, p _x ,z, p _z , σ=s?v ₀·t,p _σ=ΔE/E ₀ of the fully six-dimensional formalism. This work is an extension of earlier calculations on transverse space charge forces [1] to include the synchrotron oscillations. The extension is achieved by defining a 6-dimensional ellipsoid in thex?p _x ?z?p _z ?σ?p _σ space. The motion of this ellipsoid under the influence of the external fields and the instantaneous space charge forces can be described by six generating orbit vectors which can be combined into a 6-dimensional matrixB(s). This “bunch-shape matrix”,B(s), contains complete information about the configuration of the bunch. The solution of the equations of motion is carried through in the thin lens approximation. The formalism can also encompass acceleration by cavity fields.     

Analyzing power measurements for n-p scattering between 13.5 and 16.9 MeV

The analyzing power A_γ(θ) for neutron-proton scattering has been measured for θ = 90°(c.m.) from 13.5 to 16.9 MeV and from θ = 50° to 145°(c.m.) at 16.9 MeV. Extensive Monte Carlo calculations have been made to correct for multiple scattering effects. Overall uncertainties are about ± 0.002. All the A_γ(θ) data, but primarily those at 16.9 MeV, disagree with predictons based on the phase-shift sets which have been derived previously by way of global analyses of nucleon-nucleon scattering data. Data for the product σ(θ)A_γ(θ) have been fitted with an expansion of the form (sin θ)($\text{a}{}_0\text{+ a}{}_1\text{cos}\text{θ + a}{}_2\text{cos}{}^2\text{θ)}$. For the first time the need for a non-zero a₂ has been illustrated for energies below 20 MeV. This parameter is shown to be related to the nucleon-nucleon F-state spin-orbit phase parameter. In addition, the P, D, and F spin-orbit phase parameter values derived from the present data differ significantly from the ones based on the Yale-IV and Liver-more-X global analyses. The derived D and F spin-orbit phase parameters also differ from those obtained in the recent analysis of nucleon-nucleon scattering data by Arndt et al.     

Light-induced ultrafast phase transitions in VO2 thin film

Vanadium dioxide shows a passive and reversible change from a monoclinic insulator phase to a metallic tetragonal rutile structure when the sample temperature is close to and over 68 °C. As a kind of functional material, VO₂ thin films deposited on fused quartz substrates were successfully prepared by the pulsed laser deposition (PLD) technique. With laser illumination at 400 nm on the obtained films, the phase transition (PT) occurred. The observed light-induced PT was as fast as the laser pulse duration of 100 fs. Using a femtosecond laser system, the relaxation processes in VO₂ were studied by optical pump-probe spectroscopy. Upon a laser excitation an instantaneous response in the transient reflectivity and transmission was observed followed by a relatively longer relaxation process. The alteration is dependent on pump power. The change in reflectance reached a maximum value at a pump pulse energy between 7 and 14 mJ/cm². The observed PT is associated with the optical interband transition in VO₂ thin film. It suggests that with a pump laser illuminating on the film, excitation from the d_θ,? - state of valence band to the unoccupied excited mixed d_θ,?-π* - state of the conduction band in the insulator phase occurs, followed by a resonant transition to an unoccupied excited mixed d_θ,?-π* - state of the metallic phase band.     

Spin-polarized transport in one-dimensional waveguide structures with spatially-periodic electronic and magnetic fields

We investigate theoretically the spin-polarized transport in one-dimensional waveguide structure with spatially-periodic electronic and magnetic fields. The interplay of the spin-orbit interaction and in-plane magnetic field significantly modifies the spin-dependent transmission and the spin polarization. The in-plane magnetic fields increase the strength of the Rashba spin-orbit coupling effect for the electric fields along y axis and decrease this effect for reversing the electric fields, even counteract the Rashba spin-orbit coupling effect. It is very interesting to find that we may deduce the strength of the Rashba effect through this phenomenon.     

Absence of periodic solutions to scale invariant classical field theories

It is shown that in 3 + 1 Minkowski space classical field theories with energy-momentum θ_μν(x,t) satisfying θ₀₀(x,t) ? 0 and θ_μ^μ(x,t) = 0 have no finite energy periodic (or static) solutions. In particular this rules out classical glueball solutions. to Yang-Mills theories with compact gauge groups.     

Numerical simulation study on spin resonant depolarization due to spin-orbit coupling

The spin polarization phenomenon in lepton circular accelerators had been known for many years.It provides a new approach for physicists to study the spin feature of fundamental particles and the dynamics of spin-orbit coupling,such as spin resonances.We use numerical simulation to study the features of spin under the modulation of orbital motion in an electron storage ring.The various cases of depolarization due to spin-orbit coupling through an emitting photon and misalignment of magnets in the ring are discussed.     

A novel “magnetic” field and its dual non-commutative phase space

In this Letter we have studied a new form of non-commutative (NC) phase space with an operatorial form of noncommutativity. A point particle in this space feels the effect of an interaction with an “internal  ” magnetic field, that is singular at a specific position θ⁻¹${\theta }^{\mathrm{-1}}$. By “internal” we mean that the effective magnetic fields depends essentially on the particle properties and modifies the symplectic structure. Here θ is the NC parameter and induces the coupling between the particle and the “internal” magnetic field. The magnetic moment of the particle is computed. Interaction with an external physical magnetic field reveals interesting features induced by the inherent fuzziness of the NC phase space: introduction of non-trivial structures into the charge and mass of the particle and possibility of the particle dynamics collapsing to a Hall type of motion. The dynamics is studied both from Lagrangian and symplectic (Hamiltonian) points of view. The canonical (Darboux) variables are also identified. We briefly comment, that the model presented here, can play interesting role in the context of (recently observed) real space Berry curvature in material systems.