Josephson and single-particle currents between partially dielectricized superconductors with charge-density waves

The amplitudes of the nonstationary Josephson current I ¹, the interference current I ², and the quasiparticle current J through symmetric and asymmetric tunnel junctions, including superconductors with charge density waves, are calculated. In the symmetric (s) case the dependence of the Josephson current I _s ¹ on the voltage V on the junction has a logarithmic singularity at |eV|=2Δ, Δ+D, and 2D, where , Δ and Σ are the superconducting and dielectric order parameters, and e is the unit charge. At temperatures T≠0 jumps appear in the current-voltage characteristics I _s ¹ (V) at |eV|=D−Δ. Jumps and singularities are observed in the currents I _s ² and J _s at the same voltages at which singularities and jumps appear in I _s ¹ , respectively. In the nonsymmetric (ns) junctions which include an ordinary superconductor, singularities and jumps occur at |eV|=D+Δ_BCS, Δ+Δ_BCS, and (for T≠0) |D−Δ_BCS| and |Δ−Δ_BCS|, where Δ_BCS is the order parameter of an ordinary superconductor. The quasiparticle current J _ns is an asymmetric function of the voltage V and does not depend on the sign of Σ. The results are compared with experiment. Fiz. Tverd. Tela (St. Petersburg) 39, 991–999 (June 1997)     

Insulating phases of the one-dimensional t-J model with nearest-neighbor repulsive interaction

Using the deformed Hubbard operator approach, we analytically study weak-coupling phase diagram of the one-dimensional t-J-V model at half filling. In the case of small deformed parameter ζ(≪1), the interactions induced by the no double occupancy constraint are softened, accessible by the bosonization field theory and the renormalization group technique. The ground state exhibits insulating behavior of density-wave correlations. The bond-spin-density-wave (BSDW) and bond-charge-density-wave (BCDW) phases are realized in the whole weak-coupling regime while the charge-density-wave (CDW) and spin-density-wave (SDW) phases depend on V/J > (V/J) _c or V/J < (V/J) _c , where (V/J) _c = 1/4. Furthermore, our results are expected to adiabatically continue back to ζ = 1.     

New physics hints in B decays and collider outlook

There are currently two hints for new physics involving CP violation in b → s transitions: ΔS ≡ S _f − S _J ^ϕK ≠ 0, and difference in direct CP asymmetry ΔA _Kπ ≡ A _K+π ⁰ − A _K+π ⁻ ≠ 0. We explore the two scenarios with a large and unique new CP phase in b ↔ s transitions. Motivated by ΔS ≠ 0, we update on the right-handed strange-beauty squark sb _1R at TeV scale. Motivated by ΔA _Kπ ≠ 0, we explore sequential fourth generation t′ and b′ quarks. Both scenarios can survive constraints such as SM level b → sγ, sll and B _s mixing, and predict sizable CP violation in B _s mixing. The fourth generation picture predicts sizable K _L → π ⁰ vv. Direct search for sb _R, b′ and t′ at hadronic colliders, such as Tevatron Run II and LHC, can complement further CP violation studies at these machines, as well as at the future Super B factory.     

The multiphoton ionization rate and the energy shift of atoms interacting with weak dichromatic fields with commensurate frequencies are simple functions of the phase difference

By implementing a time-independent, nonperturbative many-electron, many-photon theory (MEMPT), cycle-averaged complex eigenvalues were obtained for the He atom, whose real part gives the field-induced energy shift, Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ), and the imaginary part is the multiphoton ionization rate, Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ), where ω is the frequency, F is the field strength and ϕ is the phase difference. Through analysis and computation we show that, provided the intensities are weak, the dependence of Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ) on ϕ is simple. Specifically, for odd harmonics, Γ varies linearly with cos(ϕ) whilst for even harmonics it varies linearly with cos(2ϕ). In addition, this dependence on ϕ holds for Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ) as well. These relations may turn out to be applicable to other atomic systems as well, and to provide a definition of the weak field regime in the dichromatic case. When the combination of (ω ₁, F ₁) and (ω ₂, F ₂) is such that higher powers of cos(ϕ) and cos(2ϕ) become important, these rules break down and we reach the strong field regime. The herein reported results refer to Γ(ω ₁, F ₁;ω ₂, F ₂,ϕ) and Δ(ω ₁, F ₁;ω ₂, F ₂,ϕ) for He irradiated by a dichromatic ac-field consisting of the fundamental wavelength λ = 248 nm and its 2nd, 3rd and 4th higher harmonics. The intensities are in the range 1.0×10¹²-3.5×10¹⁴ W/cm², with the intensity of the harmonics being 1-2 orders of magnitude smaller. The calculations incorporated systematically electronic structure and electron correlation effects in the discrete and in the continuous spectrum, for ¹S, ¹P, ¹D, ¹F, ¹G, and ¹H two-electron states of even and odd parity. Received 9 July 2000 and Received in final form 2 November 2000     

High-spin states in <Superscript>36</Superscript>Ar and their underlying shell model configurations

Eight high-spin states in ³⁶Ar below 10MeV excitation energy, among them a prospective J ^π = 8^- state at 9408keV and the J? 8 levels of the recently discovered superdeformed rotational band, have been observed by n-γ coincidence measurements with the ³³S(α, nγ) reaction at E _α = 14.4 and 13.4MeV. High-spin assignments of, respectively, J ^π = 6⁺ and 5^- were obtained for the E _p = 1209 and 1462keV (E _x = 9682 and 9927keV) resonances of the ³⁵Cl (p,γ) reaction by a measurement of γ-ray angular distributions. The spectrum of the high-spin and of the E _x? 7.4MeV levels is decomposed according to the underlying shell model configurations with n = 0, 1, 2, 4 particles excited from the N = 2 into the N = 3 major shell. The role of four-particle excitations, all connected with large prolate distortions, is elucidated for the entire A = 36-40 mass region. Received: 21 December 2001 / Accepted: 25 March 2002     

Single α-particle orbits and Bose-Einstein condensation in <Superscript>12</Superscript>C

Bosonic properties of α particles such as single-α orbits and occupation numbers in J^π = 0⁺, 2⁺, 1^- and 3^- states of ¹²C around the 3α threshold are investigated with the semi-microscopic 3α cluster model. As in other studies, we found that the 0⁺₂ (2⁺₂) state has dilute-3α-condensate-like structure in which the α particle is occupied in the single S (D) orbit with about 70% (80%) probability. The radial behaviors of the single-α orbits as well as the occupation numbers are discussed in detail in comparison with those for the 0⁺₁ and 2⁺₁ states together with the 1^-₁ and 3^-₁ states.     

Covariant tensor formalism for partial-wave analyses of ψ decays into γB¯, γγV and ψ(2s)↦γχ<Subscript>c0,1,2</Subscript> with χ<Subscript>c0,1,2</Subscript>↦K¯πand 2π<Superscript>+</Superscript>2π<Superscript>-</Superscript>

With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial-wave analysis (PWA). Among them, ψ↦γpˉ,γΛˉ,γΣˉ,γΞˉ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays ψ↦γγV with V ≡ ρ,ω,φ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity (C = +) and mass above 1 GeV through ψ↦γR↦γγV; ψ(2s)↦γχ_c0,1,2 with χ_c0,1,2↦Kˉπ⁺π^- and 2π⁺2π^- decays are good processes to study χ_cJ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels.     

Wave mechanics of two hard core quantum particles in A 1-D box

The wave mechanics of two impenetrable hard core particles in a 1-D box is analyzed. Each particle in the box behaves like an independent entity represented by a macro-orbital (a kind of pair waveform). While the expectation value of their interaction, 〈 V _HC (x) 〉, vanishes for every state of two particles, the expectation value of their relative separation, 〈 x 〉, satisfies 〈 x 〉≥λ/2 (or q ≥ π/d, with 2d=L being the size of the box). The particles in their ground state define a close-packed arrangement of their wave packets (with 〈 x 〉= λ/2, phase position separation Δϕ = 2π and momentum |q _o| = π/d) and experience a mutual repulsive force (zero point repulsion) f _o =h ²/2md ³ which also tries to expand the box. While the relative dynamics of two particles in their excited states represents usual collisional motion, the same in their ground state becomes collisionless. These results have great significance in determining a correct microscopic understanding of widely different many-body systems.     

Effect of non-zero Schottky barrier on the J-V characteristics of organic diodes

Current-voltage (J -Vcharacteristics of poly(3-hexylthiophene) (P3HT) are studied at different temperatures upto high voltages ∼ 20 V in the hole-only device configuration. The characteristics are studied in the temperature range 310-210K. In the intermediate voltage range the J -V characteristics follow J V ^l+1 , where l > 1 . As the voltage increases to high values J still varies as a power law i.e. as V^m, but contrary to the literature result m becomes < 2 . This behavior is explained theoretically in terms of non-zero injection Schottky barriers. The complete analytical expressions for the actual trap filled limit voltage (V′ _TFL) and J -V curves beyond V′ _TFL are presented.     

Interaction of both charge density waves in NbSe3 from interlayer tunneling experiments

An interlayer tunneling technique has been used for spectroscopy of charge density wave (CDW) energy gaps (Δ_1,2) in NbSe₃ subsequently opened at the Fermi surface on decreasing temperature at T _p1 = 145 K (CDW1) and at T _p2 = 60 K (CDW2). We found that the CDW2 formation is accompanied by an increase of the CDW1 gap below T _p2. The maximum enhancement of Δ₁, δΔ₁ is about 10%. The effect observed has been predicted theoretically as resulting from the joint phase locking of both CDWs with the underlying crystalline lattice below T _p2. The text was submitted by the authors in English.     

Power law distributions and dynamic behaviour of stock markets

A simple agent model is introduced by analogy with the mean field approach to the Ising model for a magnetic system. Our model is characterised by a generalised Langevin equation = F ϕ + G ϕ t where t is the usual Gaussian white noise, i.e.: t t ^′ = 2Dδ t-t ^′ and t = 0. Both the associated Fokker Planck equation and the long time probability distribution function can be obtained analytically. A steady state solution may be expressed as P ϕ = exp{ - Ψϕ - ln G(ϕ)} where Ψϕ = - F/ G dϕ and Z is a normalization factor. This is explored for the simple case where F ϕ = Jϕ + bϕ² - cϕ³ and fluctuations characterised by the amplitude G ϕ = ϕ + ɛ when it readily yields for ϕ≫ɛ, a distribution function with power law tails, viz: P ϕ = exp{2bϕ-cϕ² /D}. The parameter c ensures convergence of the distribution function for large values of ϕ. It might be loosely associated with the activity of so-called value traders. The parameter J may be associated with the activity of noise traders. Output for the associated time series show all the characteristics of familiar financial time series providing J < 0 and D≈ | J|. Received 25 July 2000     

Search for the f1(1285) → π+π-π0 decay with the VES detector

The isospin-violating decay f ₁(1285) → π⁺π^-π⁰ has been studied at the VES facility. This study is based on the statistics acquired in π^- Be interactions at 27, 36.6 and 41 GeV/c in the diffractive reaction π^- N → (f ₁π^-)N . The f ₁(1285) → π⁺π^-π⁰ decay is observed. The preliminary ratio of decay probabilities BR(f ₁(1285) → π⁺π^-π⁰) to BR(f ₁(1285) → ηπ⁺π^-)^. BR(η → γγ) is ∼ 2% . Original article based on material presented at HADRON 2007.     

Observation of the 7 MeV excited spin-flip and non-spin-flip partners in 16 ΛO by γ -ray spectroscopy

We have observed three γ -ray transitions in _Λ ¹⁶ O from both 7MeV excited spin-flip and non-spin-flip partners ( 2^-, 1^- ₂ to the ground-state doublet ( 1^- ₁, 0^- via the ¹⁶O(K ^-,π^-) reaction. The 7MeV excitation energies of the spin-doublet members ( 2^-, 1^- ₂ were determined to be 6784±4±4 keV and 6562±1±2 keV, respectively, and thus the spacing was obtained to be 222±4±5 keV. This is the first observation of the spin-flip state directly populated by the ( K ^-,π^- reaction. Moreover, such directly populated spin-flip and non-spin-flip partners were resolved for the first time.     

PHENIX study of dihadron correlation in Au+Au collision at ?{sNN } \sqrt {s_{NN} } = 200 GeV: jet quenching and medium response

We provide a detailed survey study of dihadron azimuthal angle (Δϕ) correlations in a broad range of transverse momentum (0.4 < p _T < 10 GeV/c) and centrality (0–92%) in Au+Au collisions at 149-2 = 200 GeV. The evolution of the jet shape and yield with p _T seems to suggest two distinct components at the away-side pairs: a suppressed jet fragmentation component around Δϕ ∼ π, and a medium-induced components around |Δϕ − π| ∼ 1.1. The former dominates p _T > 5 GeV/c and the later dominates at p _T < 4 GeV/c.     

Study of N*(1440) from J/Ψ decays

For J/Ψ↦ pπ⁰ and pπ⁺π^-, the π⁰ p and pπ⁺π^- systems are limited to be pure isospin-(1/2) due to isospin conservation. This is a big advantage in studying N^* resonances from J/Ψ decays, compared with πN and γN experiments. The process J/Ψ↦ N ^* or p provides a new way to probe the internal structure of the N^* resonances. Here we report a quark model calculation for J/Ψ↦ p, N ^*(1440) and N ^*. The implication for the internal structure of N ^*(1440) is discussed. Received: 1 June 2001 / Accepted: 20 June 2001     

Di-pion emission in heavy quarkonia decays

The dipion spectrum for the ϒ(nS) → ϒ(n′S) transition with n < 4 has the form dw/dq ∼ (phase space) |η − x|², with x = q ² − 4m _π² / (ΔM)² − 4m _π² < q ² ≡ M _ππ², and ΔM = M(nS) − M(n′S). The parameter η is calculated and the spectrum is shown to reproduce the experimental data for all three types of decays: 3 → 1, 2 → 1, and 3 → 2 with η ≈ 0.5, 0, and −3, respectively. The text was submitted by the author in English.     

Phase-sensitive reentrance into the normal state of mesoscopic SNS structures

Normal (N) metallic (Ag) mesoscopic conductors with two superconducting (S) faces (Al), arranged mirror-symmetrically relative to the streamlines of the current, periodically switch into the normal state as the superconducting phase difference Δϕ between the NS boundaries approaches the values Δϕ =(2n+1)π, n=0,1,2,..., irrespective of temperature and applied voltage. For Δϕ =2nπ and low applied voltages the conductance passes through a maximum and approaches the normal value as temperature decreases (reentrance). As the voltage subsequently increases, the conductance increases and passes through a maximum. As the phase difference moves away from the values Δϕ=2nπ, the maxima shift in the direction of low temperatures and voltages. The latter result shows unequivocally that in our metal structures it is necessary to take into account the next-order corrections to the “weak” proximity effect approximation. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 489–494 (10 April 1998)     

Partial wave analysis of πproduction in two-photon collisions at LEP

The reaction γγ → π⁺π^-π⁰ with quasi-real photons is studied with a total integrated luminosity of 663pb^-1, collected by the L3 detector at LEP at center-of-mass energies from 183 to 209GeV. The results of an energy-dependent partial wave analysis in the mass region 1.1≤M(π⁺π^-π⁰)≤2.2GeV are presented. The reaction is dominated by a₂(1320) formation. A strong signal consistent with the first radial excitation of the isovector tensor state, a₂(1700), is present and confirms the previous L3 observation. Its two-photon partial width is found to be Br(3π) = 0.37^+0.12_-0.08keV, the relative branching ratio of ρ(770)π to f₂(1270)π is 3.4±0.4. For all observed states the product of γγ partial width and 3π branching ratios is measured.     

Dimer state in the two-dimensional anisotropic alternated-exchange Heisenberg model

An analysis is made of the two-dimensional Heisenberg model with S=1/2, anisotropic exchange interaction between nearest neighbors, and alternating exchange in two directions, [100] and [010] (corresponding to condensation of the (π, π) mode) and in one direction [100] (corresponding to condensation of the (π, 0) mode). The quantum Monte Carlo method is used to calculate the thermodynamic characteristics and the spin correlation functions which are used as the basis to determine the boundary of stability of an anisotropic antiferromagnetic with respect to alternation of exchange δ=(1−J ^x,y /J ^z )^0.4 in the (π,π) model and δ=(1−J ^x,y /J ^z )^0.31 in the (π,0) model. In the (π,0) model a disordered quantum state exists in the range (1−J ^x,y /J ^z )^0.31<δ<(0.3–0.35). The energy (E−0.68)=0.36δ ^1.80(6) and 0.21 δ ^2.0(5), the energy gap between the ground and excited states H _c (δ)=1.96δ ^2.(1), 1.8(1) (δ−0.35(3))^0.67(2) were determined as a function of the alternation of exchange in the (π,π)-and (π,0) models, respectively. Fiz. Tverd. Tela (St. Petersburg) 40, 1080–1085 (June 1998)     

Effect of magnetic field on the sound velocity of a dilute Kramers-ion glass at low temperature

Recent results on the effect of magnetic field on the sound velocity V in aluminosilicate glasses doped with dysprosium are analyzed on the basis of a minimal model for the ground state of Dy³⁺ (Kramers ion with J=15/2) described by a wave function ϕ _± = ϕ _± J _m + ηϕ _{± 1/2}. The first term represents a state with a large J projection on the local crystal field axis and the random parameter η(〈η〉=0, 〈η ²〉≪1) introduces a small admixture of the state ϕ _±1/2 into the ground state. The relative variation of V due to the resonance interaction of sound waves with this state split by H is determined as a function of H and T. It possesses a universal asymptotic behavior. Our results are in reasonable agreement with the experiment. A possible structure of the crystal fields that can induce this state is discussed. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 341–346 (25 February 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.