On a soluble model of an antiferromagnetic chain with alternating interactions and magnetic moments

The one-dimensional anisotropic XY model with alternating nearest-neighbour interactions and magnetic moments is investigated. The singularities of the susceptibility χ_zz in the ground state are studied in detail. In the general anisotropic case χ_zz can exhibit two logarithmic singularities at two different values of the applied magnetic field b. If the interactions satisfy a certain relation which will be reffered to as the pseudoisotropic condition (which includes the isotropic case), χ_zz can have two power-$\text{1}\text{2}$ singularities at the upper side of the lower critical field and the lower side of the upper critical field. Deviations from this behaviour which occur for special values of the interaction constants are discussed in some detail. Finally the specific heat is studied in the low- and high-temperature limits.     

|ΔI| = 12 rule in non-leptonic weak interactions with Han-Nambu quarks

Gauge theories of weak and electromagnetic interactions involving Han-Nambu quarks are constructed with the following features: small $\text{K}{}_{\mathrm{<mtext>L</mtext>}}\text{→ μ}\text{μ}$ amplitude and K_L - K_S mass-splitting; a non-leptonic effective Lagrangian ΔY = ± 1 leading to the usual soft-pion theorems and obeying a fundamental $\text{|ΔI| =}\text{1}\text{2}$ rule, with corrections of order θ²_Cabibbo.     

On the cyclotron resonance width of an electron impurity system in two dimensions

Using the proper connected diagram expansion which incorporates the quasi-particle effect naturally we calculated the cyclotron resonance width γ in the extreme quantum limit.(a) γ ∝n

$\text{1}\text{2}$

_s B

$\text{1}\text{2}$

for a short range interaction, and (b) γ = π

$\text{1}\text{2}$

ze² κ^-1 <?crossed h.c.h;^-1 n

$\text{1}\text{2}$

_s for Coulomb interaction, are obtained. The field (B) and concentration (n_s)-dependence is in satisfactory agreement with experimental data. The variation γ = (γ²₁ + γ²₂ + …)

$\text{1}\text{2}$

of Matthiessen's rule γ = γ₁ + γ₂ + …, holds when there exist scattering centers of different kinds in the system.     

On the presence of the S4z-term in Fe(HCOO)2 · 2H2O

The magnetic specific heat of ferrous formate dihydrate is analysed on the basis of a model, $\text{S}{}_{\mathrm{A}}\text{=}\text{1}\text{2}$ and S_B = 2. The experimental result turns out to be well explained by the introduction of a large S⁴_z-term for B site ions.     

Excitation spectrum and T=0 dynamics of the one-dimensional planar spin-12 ferromagnet

The T=0 dynamics of the one-dimensional $\text{S}\text{=}\text{1}\text{2}$ ferromagnet with planar exchange anisotropy is studied by finite-chain calculations and a Green function approach. We demonstrate that the excitation spectrum relevant for appropriate low-T inelastic neutron scattering experiments is much more complex than predicted by linear spin-wave theory. It includes two continua and a set of discrete branches. Some of the low-lying excitations predicted by rigorous calculations, on the other hand, are shown to contribute no spectral weight to the T=0 dynamic structure factor S_zz(q,ω). We provide quantitative results for the spectral-weight distribution in S_zz(q,ω) at T=0 from bound states and continuum states, including a detailed analysis of the singularity in S_zz(q,ω) at the lower band edge. Further evidence is found for the prediction that some T=0 critical properties of the planar $\text{S}\text{=}\text{1}\text{2}$ ferro- and antiferromagnet are governed by exponents which depend continuously on the planar anisotropy.     

Exciton binding energy in GaAs quantum wells deduced from magneto-optical absorption measurement

Magneto-optical absorption spectra due to exciton states and Landau-levels were measured in GaAs/AlAs multi-quantum-wells. By extrapolating the photon energies of the absorption peaks to zero magnetic field, the lowest state (1S) heavy hole exciton binding energy, E^B_$\text{h}$(1S), was obtained as a function of well size L_z in the range $\text{58}\text{A}\text{?}\text{?}\text{L}{}_{\mathrm{z}}\text{?252}\text{A}\text{?}$. The L_z dependence of E^B_h showed the change of the exciton character from three-dimensional to two-dimensional with decreasing L_z. The diamagnetic shift observed for the heavy hole exciton peak was larger than that for the light hole exciton peak, showing the anisotropic nature of the Luttinger-Kohn Hamiltonian. The diamagnetic shift of the heavy hole exciton peak became smaller as L_z was decreased, suggesting the enhancement of the two-dimensional exciton character.     

Effect of the frustration to the ground state energy and entropy of the spin-glass in the random bond Ising model on the square lattice

The energies and the entropies of the spin-glass state and the paramagnetic state at T = 0 of the random-bond Ising mixture of the ferromagnetic bond (concentration p) and the antiferromagnetic bond (concentration 1 ? p) on the square lattice are calculated by the method of the square approximation in the simple version. A self-consistent relation that the partial trace of the normalized density matrix of the square cluster is equal to that of the vertex ($\text{tr}\text{(}{}_{\mathrm{jkl}}\text{?}\text{?}{}^{\mathrm{(4)}}\text{(i,j,k,l) =}\text{?}\text{?}{}^{\mathrm{(1)}}\text{(i)}$) leads to an integral equation for the distribution function of the effective fields, and it is solved exactly at T = 0. The symmetric solution of the integral equation contains the paramagnetic state and two spin-glass states, SG1 and SG2. The energies and the entropies of these states are obtained as functions of the concentration p. The values of the energies per spin at $\text{p =}\text{1}\text{2}$ are -0.75|E_F|, -0.72746|E_F|, -0.72543|E_F|, and correspond to a minimum, a saddle point, and a maximum, respectively, and the values of the entropies are 0, 0.082886k_B, and 0.054457k_B, respectively. The present results are compared with those of the pair approximation and discussed.     

A phenomenological bound for charged and neutral D meson life times

It is shown that recently reported branching ratios of $\text{D}\text{→}\text{K}\text{π}$ and Δ = 1 property of weak nonleptonic hamiltonian for ΔC =ΔS = ±1 processes as give a phenomenological bound for χ(D⁺)/χ((D⁰). Also, using previously calculated values of χ(D→ e^±X), the total widths of neutral and charged D mesons are guessed and their life times turn out to be rather short.     

Two-magnon Raman scattering in the two-dimensional antiferromagnet K2FeF4

Two-magnon Raman scattering in the planar quadratic antiferromagnet K₂FeF₄ is investigated. The temperature dependence of the energy shift is in good agreement with second-order Green-function theory, as is the linewidth at low temperature. Numerical results, including renormalization, are the Heisenberg exchange $\text{J}\text{k}{}_{\mathrm{B}}\text{= ?14.5 ± 0.7}\text{K}$ and the anisotropy $\text{Δ(T = 0) = gμ}{}_{\mathrm{B}}\text{H}{}_{\mathrm{A}}\text{4|J|S = 0.18 ± 0.05}$, but with $\text{J[1 + Δ(T = 0)]}\text{k}{}_{\mathrm{B}}\text{= ?17.06 ± 0.10}\text{K}$.     

Transfer of rotational population in CO by IR laser double resonance

A double resonance experiment on CO using two CO lasers (pump on v = 1 → 0, probe on v = 2 → 1) is described. Molecular diffusion has to be considered to reduce the data. The total rotational relaxation rate constant for J = 10 is found to be 1.25 ± 0.15 s^-1 torr^-1. Population transfer seems to proceed for $\text{2}\text{3}$ by |ΔJ| = 1 and for $\text{1}\text{3}\text{by |ΔJ| =2}$.     

Critical behaviour of a uniaxial ferromagnet,ErCl3·6H2O with predominant dipolar interactions

The parallel magnetic susceptibility χ of a uniaxial ferromagnet ErCl₃·6H₂O has been measured between 0.3 and 4.2K and specially near T_c = 0.353 K. The predominant contribution to the Curie-Weiss temperature is due to the dipolar interactions. χ is proportional to ?^?γ with $\text{? =}\text{T}\text{T}{}_{\mathrm{c}}\text{?1}$ in the range 10^?3 < ? < 5 × 10^?2. The γ value, γ = 1.01 ±0.03 is consistent with the theoretical prediction for a uniaxial dipolar ferromagnet.     

Quasiclassical mobility for extrinsic semiconductors

A quasiclassical formulation for mobility in extrinsic semiconductors is presented based on scattering from ionized impurity atoms. Quantum theory enters the otherwise classical Chapman-Enskog expansion of the Boltzmann equation through incorporation of the Thomas-Fermi interaction potential together with the Bom approximation for evaluation of scattering integrals. The following expression results for mobility μ_i, (cgs):

$\text{μ}{}_{\mathrm{i}}\text{3}\text{2}\text{?}{}^2\text{n}{}_{\mathrm{s}}\text{e}{}^3\text{m}{}^1\text{2}\text{2}\text{k}{}_{\mathrm{B}}\text{T}\text{2φ}\text{3}\text{2}\text{1}\text{f(γ)}$

,

$\text{f(γ)=[(1+γ)e}{}^{\mathrm{\gamma }}\text{E}{}_1\text{(γ)?1]}$

, where n_s is impurity concentration, m¹ is effective mass, E₁(γ) is the exponential integral, ? is dielectric constant and γ is dimensionless Thomas-Fermi energy. The structure of the dimensional factor in the preceding expression for μ_i agrees with previous expressions for this parameter.     

Pairing-isopairing competition in odd-odd nuclei

We discuss the systematics of 0⁺, v = 0, T = |T_Z| + 1 levels in odd-odd nuclei and conclude about the ground state isospin and seniority of these nuclei. For N = Z nuclei starting from the $\text{1f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ shell v_g.s = 0 |T_g.s = |T_z + 1. Otherwise v_g.s = 2, T_g.s = |T_z|.     

Unified theory of weak and electromagnetic interactions with ΔI = 12 rule

An SU(2) ? U (1) gauge theory of weak and electromagnetic interactions satisfying the $\text{ΔI =}\text{1}\text{2}$ rule is proposed, which has the following characteristic: (i) A neutral boson Z, coupling to the neutral strangeness-changing current is used in addition to the usual charged ones, to give the $\text{ΔI =}\text{1}\text{2}$ rule in the standard fashion. Couplings are chosen such that the Z decouples from the observed leptons, in order to agree with experiment. (ii) It is assumed that the |ΔY| = 2 transitions due to neutral vector-boson exchange cancel the |ΔY| = 2 contributions due to charged vector-boson exchange. This constraints the Cabibbo angle in a manner consistent with experiment.     

Calculation of a pair correlation function for the three-dimensional Ising model with long-range exchange forces

A simple difference equation for one type of correlators has been obtained by the method of direct calculation of the correlation functions (CF). It is correct for the Ising model of an arbitrary dimension with the exactness $\text{O}$($\text{1}\text{z}$) (z-number of particles covered by the interaction potential). The equation obtained is used to calculate the pair CF 〈S^z_fS^z_j〉 in the three-dimensional Ising model with long-range forces which are of importance when dealing with the applied magnetic problems. The results of the calculations lead to corrections in the Ornstein-Zernike (OZ) theory.     

Variational calculations of realistic models of nuclear matter

We report variational calculations of nuclear matter with a semi-realistic Reid v₁₂ model, and a realistic v₁₄ model of the two-nucleon interaction operator. The v₁₄ model fits the available nucleon-nucleon scattering data up to 425 MeV lab energy, and has relatively weak L² and $\text{(}\text{L}\text{·}\text{S}\text{)}{}^2$ interactions in addition to the standard central, tensor and ($\text{L}\text{·}\text{S}$). The L² and $\text{(}\text{L}\text{·}\text{S}\text{)}{}^2$ interactions are treated semiperturbatively; their contribution reduces the overbinding of nuclear matter. However, the equilibrium k_F = 1.7 fm^?1 and E₀ = ?17.5 MeV obtained with the v₁₄ model are both higher than their empirical values k_F = 1.33 fm^? and E₀ = ?16 MeV. We assume that the difference between the calculated and empirical E(ρ) is entirely due to three-nucleon interactions (TNI). The TNI contributions are phenomenologically added to the nuclear matter energy, and their parameters are adjusted to obtain the correct equilibrium energy, density and compressibility. The required TNI contributions appear to be of reasonable magnitude.     

Critical field and specific heat of the anisotropic superconductor Nb3S4

We report on the first measurements of the critical field B_c2 and the specific heat of Nb₃S₄, which is a linear structured compound with a superconducting transition temperature of 3.65 K. The angular dependence of B_c2 is well described by the effective-mass model. The ratio of the critical fields parallel and perpendicular to the c-axis gives a value of 4.6. The small value of the specific heat jump at $\text{T}{}_{\mathrm{c}}\text{(}\text{Δc}\text{γT}{}_{\mathrm{c}}\text{= 0.95)}$ can be explained with an anisotropic gap function.     

Magnetoreflectance of the Γ6 – Γ8 exciton ground state in cubic ZnSe

Magnetoreflectance measurements on the ground state of the Γ₆ – Γ₈ free exciton in cubic ZnSe in magnetic fields up to 18 T are reported. The splitting between the |1, ±1〉 states was derived from the measured difference spectrum between σ⁺ and σ^--polarized reflectance in Faraday configuration. The splitting between the two states corresponding to |2, 0〉 and |1, 0〉 at B = 0 was determined by means of a lineshape analysis. We derive an electron g-factor g = 1.48 ± 0.25, in reasonable agreement with existing k · p calculations, and obtain an effective hole g-value $\text{K}\text{?}\text{= -0.26±0.06}$. In addition, we find an upper limit for the short range electron-hole spin exchange energy Δ ? 0.1 meV, which is considerably smaller than values, which is considerably smaller than values reported in the literature, but agrees with recent results on ZnTe obtained by uniaxial stress and also magnetoreflectance measurements.     

Superfluidity of neutron matter: (II). Triplet pairing

The possibility of neutron triplet pairing and superfluidity in neutron star matter is investigated, and the energy gap and corresponding critical temperature is calculated or estimated as a function of Fermi momentum or density. The calculations are performed for a “one-pion-exchange gaussian” potential, and compared with the results for neutron and proton singlet pairing and superfluidity calculated earlier.The results indicate that neutron superfluidity, corresponding specifically to ³P₂ state pairing, may exist in a high-density shell in the nuclear-matter region of a neutron star, i.e. for 1.6 × 10¹⁴g/cm³ < ρ < 1.4 × 10¹⁵g/cm³, and the maximum self-consistent energy gap is Δ⁰₁k_F ≈ 0.6 MeV and Δ⁰₃(k_F) ≈ 0.1 MeV for an effective mass $\text{m}{}^1\text{≈ 0.75}\text{and}\text{k}{}_{\mathrm{<mtext>F</mtext>}}\text{≈ 2.1}\text{fm}{}^{\mathrm{?1}}$, i.e. for a mas ? ≈ 5.2 × 10¹⁴g/cm³. For $\text{m}{}^1\text{= 1.0}$ we get correspondingly Δ⁰₁(k_F) ≈ 3.3 MeV and Δ⁰₃(k_F) ≈ 0.6 MeV for k_F ≈ 2.2 fm^?1.