π-0 transition in superconductor-ferromagnet-superconductor junctions

Superconductor-ferromagnet-superconductor (SFS) Josephson junctions are known to exhibit a transition between π and 0 states. In this letter, we find the π-0 phase diagram of an SFS junction depending on the transparency of an intermediate insulating layer (I). We show that, in general, the Josephson critical current is nonzero at the π-0 transition temperature. Contributions to the current from the two spin channels nearly compensate each other, and the first harmonic of the Josephson current as a function of phase difference is suppressed. However, higher harmonics give a nonzero contribution to the supercurrent.     

Novel 0–π transitions in Josephson junctions between noncentrosymmetric superconductors

We study the Josephson effect between two noncentrosymmetric superconductors(NCSs) with opposite polarization vectors of Rashba spin–orbit coupling(RSOC).We find a 0–π transition driven by the triplet–singlet ratio of NCSs.Different from conventional 0–π transitions,the Andreev bound states change their energy range instead of phase shift in the 0–π transition found here.This novel property results in a feature that the critical current becomes almost zero at the transition point,not only a minimum.Furthermore,when the directions of RSOC polarization vectors are the same in two NCSs,the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin–orbit coupling in the interlayer.We find novel oscillations of critical current without 0–π transition.These novel 0–π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet–singlet ratio of NCSs.     

Vibrational states in U234 excited by Np234 decay and evidence for an E0-transition between states with I ≠ 0

Transitions following the EC-capture decay of 4.4-day Np²³⁴ have been investigated with 99-, 160- and 350-gauss permanent magnets, a solenoidal “long lens” spectrometer, and NaI(Tl) scintillation detectors with a 100-channel analyzer. Many internal conversion electron lines were observed, and assigned to transitions at 43.49, 99.70, 233.6, 234.6, 238.6, 247.9, 297.6, 450.5, 482.8, 485.1, 515.7, 525.9, 556.8, 744.1, 751.7, 767.9, 787.8, 793.8, 810.0, 812, 854, 1003, 1105, 1196, 1240, 1395, 1439, 1531, 1562, 1575 and 1606 keV. A few other weak electron lines were observed, but not assigned to transitions. Transitions following Np²³⁶, Np²³⁸, and Np²³⁹ decay were also observed on the same plates and identified, helping to insure correctness of the isotopic assignment of the U²³⁴ transitions. The above transitions have been interpreted to establish levels in U²³⁴ at 43.49, 143.2, 788, 812, 854, 1049, 1090, 1092, 1240, 1340, 1439, 1575 and 1606 keV. The 812-keV E0 transition has been resolved into two components, one of which is interpreted to be an E0-transition between two 2⁺ states. Transition multipolarities and possible level spin and parity assignments are discussed. A comparison of the known data on relative energies of vibrational states indicates that the β-vibrational states have lower energies than the γ-vibrational states in the few nuclei where the energies of both are known.     

Interference between KL0 and KS0 in the Kμ3 decay mode

The decay law of a coherent mixture of K_L⁰ and K_S⁰ has been studied in the K_μ3 mode. The charge asymmetry is analysed as a function of the regeneration phase arg(i ƒ₂₁) and Re(ϵ). In addition arg(i ƒ₂₁) is estimated from recent measurements of K⁺ and K⁻ absorption cross sections in carbon.     

Scattering states and bound states in λ℘(φ)2

By analyzing the Bethe-Salpeter equation for even ()₂ models we show that for weak coupling the mass spectrum is discrete and of finite multiplicity below 2m. Moreover on even states of energy less than 4(m–) we show that theS matrix is unitary. Herem is the physical mass and =()0 as 0. Our results rely essentially only on a simple assumption about the analyticity of the Bethe-Salpeter kernel which has been verified for weak coupling. For the interaction ⁴, (/m _o ² 1) we show that there are no even bound states of energy less than 4(m–).Work supported in part by NSF, Grant MPS 74-13252     

Pairwise Entanglement and Quantum Phase Transitions in Spin Systems

We examine several well-known quantum spin models and categorize the behaviour of pairwise entanglement at quantum phase transitions. A unitied picture on the connection between the entanglement and quantum phase transition in spin systems is presented.     

Controlled switching between quantum states in the exciton–polariton condensate

Optically controlled switching between modes of a polariton laser having different symmetries has been demonstrated experimentally. The microscopic shift of the optical excitation spot dramatically changes the shape of the polariton condensate formed in a cylindrical micropillar on the basis of the planar semiconductor microcavity. Switching between the ring and lobed condensate is achieved owing to the violation of the cylindrical symmetry of the effective potential formed by the lateral surface of the pillar and by the cloud of incoherent excitons created by optical pumping.     

The effect of deformed states on β− and E1 decays to the 0 and 6.06 MeV 0+ states of 16O

The ratio of transition matrix elements for decays to the 0 and 6.06 MeV 0⁺ states of ¹⁶O is calculated. The transitions considered are the β⁻ decay of the ground state of ¹⁶N and the E1 decay of the 13.1 MeV 1⁻ state in ¹⁶O. Deformed 2p-2h and 4p-4h admixtures are included in the 0⁺ states. The resulting ratios compare very favorably with recent experimental results.     

Lifetime Measurements for Electric-Dipole △n=0 Transitions in the Beryllium-Like Sulfur

We have measured lifetimes of △n=0 allowed transitions in beryllium-like sulfur using beam foil spectroscopic techniques. The measured values, derived from analysis of arbitrarily normalized decay curves, are presented and compared with theoretical calculations and previous measurements. Accurate probabilities have been determined by the well-known relationship.     

Quantum Bocce: Magnon–magnon collisions between propagating and bound states in 1D spin chains

The dynamics of two magnons in a Heisenberg spin chain under the influence of a non-uniform magnetic field is investigated by means of a numerical wave-function-based approach using a Holstein–Primakoff transformation. The magnetic field is localized in space such that it supports exactly one single-particle bound state. We study the interaction of this bound mode with an incoming spin wave and the interplay between transmittance, energy and momentum matching. We find analytic criteria for maximizing the interconversion between propagating single-magnon modes and true propagating two-magnon states. The manipulation of bound and propagating magnons is an essential step towards quantum magnonics.     

Long Range Correlations and Phase Transitions in Non-equilibrium Diffusive Systems

We obtain explicit expressions for the long range correlations in the ABC model and in diffusive models conditioned to produce an atypical current of particles. In both cases, the two-point correlation functions allow one to detect the occurrence of a phase transition as they become singular when the system approaches the transition.     

0-π transition induced by the barrier strength in spin superconductor Josephson junctions

The Andreev-like levels and the free energy of the spin superconductor/insulator/spin superconductor junction are obtained by using the Bogoliubov-de Gennes equation. The phase dependence of the spin supercurrents exhibits a 0-π transition by changing the barrier strength. The dependences of the critical current on the barrier strength and the temperature are also presented.     

The analysis of the low-lying 0+′ states in the medium-weight nuclei

The low-lying spectra of some medium-weight nuclei are analysed in terms of the Davydov non-adiabatic model. It is shown that some critical data like B(E2;0⁺′→2⁺)/B(E2;0⁺→2⁺) and the effective γ-deformation of nuclei as ^70,72,74Ge, ⁷⁶Se and perhaps other nuclei can be interpreted by means of the Davydov non-adiabatic model, where the 0⁺′ states belong to the oblate shape ellipsoid.     

Spontaneous dissociation of m≠0 positronium states in strong magnetic fields

Even for an infinitesimally slow motion in a direction transverse to a homogeneous magnetic field, any non-axially symmetric state of positronium becomes unbound beyond a critical field depending on its quantum numbers. All m≠0 bound states disappear beyond 5×10⁴T.     

Pattern Formation in Dynamic Phase Transitions

Instability is the main challenge in simulating dynamic phase transitions. For a van der Waals fluid, we introduce low order dissipative mechanisms with discrete Bhatnagar-Gross-Krook (BGK) models, including a relaxation model. In one and higher space dimensions, numerical results demonstrate the complexities of dynamics. While eventually a good separation of phases is reached, interesting wave patterns are observed at an earlier stage.     

Φπ production in\bar pp annihilation from S and P states and in J/ψ decaysannihilation from S and P states and in J/ψ decays

Recent experiments at LEAR have found surprisingly large branching ratios for reactions $\bar NN \to \phi \pi $ from S-wave initial states while noφπ production is observed from P states of the $\bar pp$ system. Also, noφπ is seen in radiative J/ψ decays even though the rate forωπ is substantial. We calculate theφπ production rates for these three cases viaKK* intermediate states and $K\bar K$ rescattering using the dispersion relation technique; we find that the largeφπ rate in $\bar pp$ annihilations from S states can be reproduced with a reasonable cut-off for the dispersion integral; for J/ψ decays the calculatedφπ rate is compatible with the observed upper limit. We would, however, expectφπ to be seen from $\bar pp$ P-states, in contrast to experimental findings. Yet the branching ratio for $\bar pp \to K*\bar K$ via isospinI = 1 of $\bar pp$ ,¹ P ₁ state is not known; and therefore no definite conclusion can be drawn. We also compare the Dalitz plots we obtain for directφ production and forφ production via rescattering. Clear differences between the two theoretical distributions are observed; yet very high precision data would be required to establish the origin — direct production or rescattering — of theφ mesons. This observation supports the use of the isobar model in data analyses.     

Vortex domain structures and dc currentdependence of magneto-resistances in magnetic tunnel junctions

Microfabrication and the magneto-transport characteristics of the magnetic tunnel junctions (MTJs) with a spin-valve-type structure of Ta (5nm)/Ni_{79}Fe_{21} (25nm)/Ir_{22}Mn_{78} (12nm)/Co_{75}Fe_{25} (4nm)/Al(0.8nm) oxide/Co_{75}Fe_{25} (4nm)/Ni_{79}Fe_{21} (20nm)/Ta(5nm) were investigated in this paper. A series of experimental data measured with a MTJ was used to verify a magnon-assisted tunnelling model and theory. Furthermore, a micromagnetics simulation shows that the butterfly-like vortex domain structures can be formed under a current-induced Oersted field, which decreases the net magnetization values of the ferromagnetic electrodes under a large dc current (i.e., in high voltage regimes). It is one of the main reasons for the tunnel magnetoresistance ratios to decrease significantly at high voltage biasing.     

Phase Transitions in Frustrated Slightly Nonstoichiometric ErBaCo4O7 + x (x ≈ 0 and 0.03) Cobaltites

JETP Letters - The results of the first experimental studies on the structural (lattice parameters) and elastic characteristics of ErBaCo4O7 + x cobaltites in the range of structural and magnetic...     

Spectral and Indo-Molecular Orbital Studies of n →∗ Transitions in Symmetric Diazines

Abstract

Experimental and theoretical (INDO-MO) studies of n → transitions have been carried out for seven symmetric diazines. In all cases, there is very good agreement between the theoretical predictions and experimental observations on the symmetry of the lowest energy n→? singlet state.     

Nuclear Masses and Nuclear Shape Transitions in Z=50—71

Some parameters and the β equation of Johansson mass formula were modified.In the fit to the experimental masses and two-neutron separation energies (S_2n) of 640 nuclides in the region of 50≤Z≤71,four free parameters are presented.The root-mean-square deviation of the mass values and S_2n are 0.827MeV and 0.406MeV respectively.The characters of transition from spherical to deformed shapes (N>90) are also reproduced by the curves of S_2n.