High-pressure induced magnetoresistance in <Emphasis Type="Italic">p</Emphasis>-InAs:Mn and <Emphasis Type="Italic">p</Emphasis>-CdGeAs<Subscript>2</Subscript>:Mn

The baric (P ≤ 5GPa) and magnetic-field (H ≤ 5 kOe) dependences of the transverse magnetore-sistance Δρ _xx /ρ₀ have been measured for p-InAs (R _H = 22.5 cm³/C, ρ = 0.15 Ω cm) and the new ferromag-netic semiconductor p-CdGeAs₂ (R _H = 5 cm³/C, ρ = 0.62 Ω cm), doped with a magnetic impurity (Mn), near the temperature T = 297 K. The dependences Δρ _xx /ρ₀ (P, H) for p-InAs:Mn and p-CdGeAs₂:Mn exhibit a magnetoresistive effect with an increase in pressure, and a pressure-induced magnetoresistance hysteresis is observed in p-CdGeAs₂:Mn with a pressure drop.     

High transverse momentum identified particle spectra in 200 GeV collisions from STAR

Significant baryon over meson enhancement was measured at RHIC in the intermediate transverse momentum range of p _T =2?4 GeV/c (“baryon-meson puzzle”). With STAR detector we were able to extend particle identification towards higher transverse momentum offering further insights into the particle production mechanisms at intermediate to high p _T . In this paper we present results on charged pion, proton and anti-proton spectra and ratios at intermediate to high p _T exploiting the relativistic rise of the specific ionization energy loss measured in the STAR Time Projection Chamber. These measurements provide valuable information about the production mechanisms of particles at intermediate p _T in relativistic heavy ion collisions, e.g. coalescence/recombination versus jet fragmentation.     

On the hole scattering anisotropy in the PbSb<Subscript>2</Subscript>Te<Subscript>4</Subscript> layered compound from data on the Nernst-Ettingshausen coefficient

Three independent components of the Nernst-Ettingshausen coefficient tensor Q _ikl are experimentally measured for an anisotropic single crystal of the p-PbSb₂Te₄ layered compound. The components Q ₁₂₃ and Q ₁₃₂ are found to be negative, whereas the component Q ₃₂₁ is positive. The experimental data on the anisotropy of the Nernst-Ettingshausen coefficient are discussed together with the available data on the thermopower, the Hall effect, and the electrical conductivity. The analysis demonstrates that the experimental data on the transport effects in p-PbSb₂Te₄ can be explained within a one-band model of the band spectrum and a mixed mechanism of hole scattering under the assumption that scattering from acoustic phonons and scattering from impurity ions are dominant in the cleavage plane and along the c ₃ trigonal axis, respectively.     

Change in the lattice properties and melting temperature of a face-centered cubic iron under compression

All four parameters of the Mie–Lennard-Jones pair interatomic potential have been determined, and the state equation (P) and baric dependences of the lattice properties of an fcc iron are calculated using a previously proposed method. The dependences have been studied for the following properties: Debye temperature; the first, second, and third Gruneisen parameters; isothermal bulk modulus B _T and B′(P); isochoric specific heat C _v and C _v ′(P); isobaric specific heat C _p ; coefficient of thermal expansion α _p and α _p ′(P); specific surface energy σ and σ′(P). Calculations performed along two isotherms (1500 and 3000 K) have shown good agreement with the experimental data. Analytical approximations of the baric dependences for B′(P), α _p (P), C _p (P), and σ′(P) have been obtained, and it is shown that at P → ∞ the functions B _T (P) and σ(P) change linearly, while the functions α _p′(P) and C _p ′(P) tend to zero. The calculated baric dependence of the melting temperature shows good agreement with the experimental data.     

<Emphasis Type="Italic">K</Emphasis><Superscript>±</Superscript><Emphasis Type="Italic">p</Emphasis> elastic scattering in the QCD inspired eikonalized model

Based on our previous study of the QCD inspired eikonalized model for describing vector meson photoproduction, pp, and \(\bar p\) p elastic scattering at high energies, we apply the mode to high energy K ^± p elastic scattering. The total cross section σ _tot(s), differential cross section dσ/dt, the ratio of the real part to imaginary part of the forward scattering amplitude ρ(s), and nuclear slope parameter function β(s) are calculated in the model. Our results show that the theoretical prediction for σ _tot(s) is in a good agreement with the experimental data within error bars of the data. For the other theoretical predictions there are no data to test the predictive power of the model. We need the corresponding experimental data to examinate the validity of our QCD inspired eikonalized model. However, our calculations clearly show that the Odderon exchange in the process makes a significant contribution to the observable of ρ(s) and β(s). Therefore, we may conclude that there is a good opportunity to find the QCD Odderon in the K ^± p elastic scattering at high energies.     

Variations in thermal properties of diamond under isothermal compression

State equation P(V/V ₀, T) and baric dependences of thermal properties of diamond have been obtained without any fitting parameters from the interatomic pair Mie–Lennard-Jones potential and the Einstein model of a crystal. Calculations have been performed along two isotherms (at T = 300 and 3000 K) up to P = 10000 kbar = 1000 GPa, i.e., to a relative volume of V/V ₀ = 0.5. The baric dependences have been obtained for the following characteristics: isothermal elastic modulus B _T and B'(P), isochoric heat capacity C _v and C _v ' (P), isobaric heat capacity C _p ; thermal expansion coefficient α _p and α _p ' (P); and specific surface energy σ, as well as its derivatives σ'(P) and σ'(T). It is shown that for P → ∞, functions B _T (P) and σ(P) vary linearly, functions B'(P), α _p (P), C _v (P), C _p (P) and σ'(P) tend to constants, while functions α _p '(P), C _v '(P), and difference C _p (P)–C _v (P) tend to zero. Good agreement with experimental data has been demonstrated.     

Stabilization of Ferromagnetism in BiFeO<Subscript>3</Subscript>:Ho at Hydrostatic Pressure

The isothermal magnetization of the Bi_{1 – x}Ho _x FeO₃ (x = 0?0.2) multiferroic has been studied at a hydrostatic pressure up to 9 GPa in the range of room temperatures. A new anomaly at P_C ≈ 3.81 GPa related to intermediate phases between the structural transition R3c → Pnma has been found against the background of the pressure-induced antiferromagnetic ordering in BiFeO₃ (BFO) at P ≈ 2.59 GPa. It is established that the ferromagnetic behavior under pressure depends on the Ho impurity concentration: P_C decreases at 0.05 ≤ x ≤ 0.1 because of the decrease in R3c bond lengths in the structure, and the stabilization of ferromagnetism is implemented at 0.1 ≤ x ≤ 0.2 probably because of the coexistence of the R3c and Pnma phases. The results of studies indicate that, in Bi_{1 – x}Ho _x FeO₃ with x = 0.2, the transition pressure P_C = 3.7 GPa exceeds the values for BFO doped with other 4f elements (Eu, Y, Sm) in the region R3c → Pnma of the transition.     

Kinetic freeze-out s pectra of identified particles produced in p–Pb collisions at $$\sqrt {s_{NN} }$$ = 5.02 TeV

We study the transverse momentum spectra of identified pions (π^– + π⁺), kaons ((K ^– + K ⁺), K ₀ ^s ), protons (p + p?) and lambda hyperons (Λ + Λ?) produced at mid-rapidity (0 < y _cm < 0.5) in most central (0?5)% p–Pb collisions at \(\sqrt {s_{NN} }\) = 5.02 TeV in comparison with a Unified Statistical Thermal Freeze-out Model (USTFM). The measurements for pions are reported upto p _T = 3 GeV, the kaons (K ^– + K ⁺) are reported upto p _T = 2.5 GeV, K ₀ ^s is reported upto p _T = 7 GeV, and the baryons (protons and lambda hyperons) are reported upto p _T = 3.5 GeV. A good agreement is seen between the calculated results and the experimental data points taken from the ALICE experiment. The transverse momentum spectra are found to be flatter for heavy particles than for light particles. Bulk freeze-out properties in terms of kinetic freeze-out temperature and the transverse collective flow velocity are extracted from the fits of the transverse momentum spectra of these hadrons. The effect of resonance decay contributions has also been taken care of.     

On the derivation of the Boltzmann-Landau equation from the quantum mechanical hierarchy

The general solution of the equation of motion for the quantum mechanical distribu tion functionf ₂(r ₁ P ₁,r ₂ p ₂;t)in the two particle space is given by means of the Schrödinger scattering functions. A special initial condition leads to the usual Boltzmann equation plus density correction terms, which depend on the scattering matrixt(p′,p). In the long wavelength limit and in lowest order oft(p′,p) the Landau corrections to the simple Boltzmann streaming part are obtained.     

A first-principle study on the phase transition,electronic structure,and mechanical properties of three-phase ZrTi<Subscript>2</Subscript> alloy under high pressure*

We employed density-functional theory (DFT) within the generalized gradient approximation(GGA) to investigate the ZrTi₂ alloy, and obtained its structural phase transition,mechanical behavior, Gibbs free energy as a function of pressure, P-V equation of state,electronic and Mulliken population analysis results. The lattice parameters andP-V EOS for α, β and ω phases revealed by ourcalculations are consistent with other experimental and computational values. The elasticconstants obtained suggest that ω-ZrTi₂ and α-ZrTi₂ are mechanically stable, and that β-ZrTi₂ is mechanically unstableat 0 GPa, but becomes more stable with increasing pressure. Our calculated resultsindicate a phase transition sequence of α → ω → β forZrTi₂. Both thebulk modulus B and shear modulus G increase linearly withincreasing pressure for three phases. The G/B values illustrated goodductility of ZrTi₂alloy for three phases, with ω<α<β at0 GPa. The Mulliken population analysis showed that the increment of d electron occupancystabilized the β phase. A low value for B '₀ is the feature of EOS for ZrTi₂ and this softness in the EOS isrepresentative of pressure induced s-d electron transfer.     

Structure-Dependent Magnetoresistance in the Zn<Subscript>0.1</Subscript>Cd<Subscript>0.9</Subscript>GeAs<Subscript>2</Subscript> + MnAs Hybrid Nanocomposite

The effect of high pressure on electron transport and on the field dependence of the transverse magnetoresistance has been studied in a hybrid nanocomposite based on the Zn0.1Cd0.9GeAs2 matrix and MnAs clusters. A record high negative magnetoresistance of ~74% is formed near a pressure-induced structural transition (P≈ 3.5 GPa). The considered scattering mechanisms include both the contribution from MnAs clusters at relatively low pressures (up to 0.7 GPa) and spin-dependent scattering by localized magnetic moments in the Mn-substituted structure of the matrix in the region of the structural transition. The presence of the positive magnetoresistance region associated with the two-band transport model in the high-pressure phase, as well as the large negative magnetoresistance, is described in the framework of the semiempirical Khosla–Fischer expression.     

Die Supraleitung von Zinn und Blei unter sehr hohem Druck

The dependence of the critical temperatureT _c upon pressureP is measured in the pressure range up to 160 kbar. The experimental technique developed for very high pressure-low temperature experiments (preceding article) is improved by introducing a double-sample electrical resistance cell. An internal pressure calibration is therefore possible at some well-established room temperature pressure reference points commonly used. Both metals, tetragonal white tin and fcc-lead, show a monotonic decrease ofT _c vs.P with upward curvature. The results recommend the use of Pb as a secondary standard for very high pressure experiments at Helium temperatures. In addition, high pressure polymorphic modifications of Sn and Pb are found to show superconductivity withT _c =(5.30±0.10) ?K for Sn III atP=113 kbar andT _c =(3.55±0.10) ?K for Pb II atP=160 kbar.     

Phasenumwandlung zweiter Art als kritische Erscheinung eines inneren Phasengleichgewichtes

It is demonstrated that the transition in a state with two internal phases is a second order phase transition. The term internal phases means phase-like regions inside the system which are not separated by boundaries in the sense of ordinary phase boundaries, and the dimensions and shape of which as well as their properties as such are object of an equilibrium. In a generalization (quasi phases) a long ranged correlation of alternating or periodical character is considered as a typical element of the low temperature state. Such states can be described thermodynamically with the help of a new pair of variablesQ-η. The transition intoQ-η-T is generally analogous to the critical point of ordinary phase transitions inP-V-T, andη ～(?t)^1/3 andC _p～(?t)^?2/3 with a small constant of proportionality are obtained (t=T-T _u). Using the Pippard-relations in the formV-V _γ=(dT _γ/dP) (S-S _γ) the low temperature behaviour of the entropy and density surface as a function ofP andT near the transition line can be completely described. E.g. the saturation magnetization of a ferromagnetic model is derived proportional to (?t)^1/3. Under the action of a magnetic field the transition will be of first order when the saturation magnetization is achieved, without the outer field being analogous toP orQ. Should only one internal phase differ from the high temperature state we obtain an edge point (x=0 analogous to theμ ₁?x-diagram of solutions) with finite jump inC _p andη～({t). A possible relationship to the BCS- model of the supraconductors is indicated.     

CARS study of deuterium clusters stabilized in solid helium

Solid deuterium clusters that for the first time have been isolated in a matrix of solid helium have been investigated at T=1.3 K and P=3 MPa by the coherent anti-Stokes Raman spectroscopy (CARS) technique. The vibronic Q₁((J=0) and Q₁(J=1) line intensity, shape, and positions have been studied as functions of ortho and para content in the solid, as well as of the size of clusters. The strong effect of Raman scattering cross-section sensitivity to the molecular environment nuclear spin state has been found in CARS: the ratio of probabilities for the scattering by para(J=1) and ortho(J=0) deuterium, which is equal to 1 in a gas, is as high as 10000 in nearly pure ortho deuterium, whereas it is about 50 in spontaneous Raman scattering. This effect has been shown to occur starting from a cluster size corresponding to the onset of the phonon band.     

A study of the nuclear-medium influence on transverse momentum of hadrons produced in deep-inelastic neutrino scattering

The influence of nuclear effects on the transverse momentum (p_T) of neutrino-produced hadrons is investigated using the data obtained with the SKAT propane-freon bubble chamber irradiated in the neutrino beam (with E _v =3–30 GeV) at the Serpukhov accelerator. It has been observed that the nuclear effects cause an enhancement of 〈p _T ² 〉 of hadrons produced in the target fragmentation region at low invariant mass of the hadronic system (2 < W < 4 GeV) and at low energies transferred to the hadrons (2 < ν < 9 GeV). At higher W and ν, no influence of nuclear effects on 〈p _T ² 〉 is observed. Measurement results are compared with predictions of a simple model, incorporating secondary intranuclear interactions of hadrons, which qualitatively reproduces the main features of the data.     

Calculation of the polarization of the recoil proton in πN-scattering near the inelastic threshold

The polarization of the recoil proton in πN-scattering has been calculated as a function of the scattering angle at the energies 150, 170, 190 MeV. It is shown that this polarization depends sensitively on the πN-scattering phase-shiftP ₁₁. Slight changes of the other phase-shifts do not affect the polarization to the same extent. New measurements of the differential cross-section and of the polarization in the process π^?+p→π^?+p are suggested. They would allow for a new precise phase-shift analysis, which could possibly determine the sign of theP ₁₁-phase at the inelastic threshold. This sign is important in connection with the bound-state picture of the nucleon.     

Electrical properties of zinc oxide under uniform pressure up to 25 GPa

The dependences of the Hall coefficient R _H (P) and resistivity ρ(P) of bulk n-ZnO crystals on hydrostatic pressure up to 8 GPa and quasi-hydrostatic pressure up to 25 GPa at T = 300 K have been measured. With an increase in pressure up to the polymorphic transition P _pt ? 9 GPa, an exponential increase in R(P) and ρ(P) is observed, which is caused by the increase in the ionization energy of the shallow-energy donor center. At P > P _pt, the resistivity decreases by several orders of magnitude.     

Optimization of the Electromagnetic (EM) Perturbative Effects Produced by High-Frequency Gravitational Waves

For the relic gravitational waves in high frequency band, we survey the electromagnetic resonance effect generated from the high frequency gravitational waves, which can be described in the transverse perturbative photon fluxes. Under the fixed tensor-scalar ratio r = 0.2, spectral index n _t = 0 and running index α _t = 0.01, we discuss several properties and quantity changes of the transverse perturbative photon fluxes, which can be improved significantly through setting the longitudinal magnetic component of background EM field in the standard gaussian form, and wave impedance analysis on the transverse direction. Through the theoretical calculation, the transverse perturbative photon fluxes can reach up to 10³ s ^?1 with some optimal parameters such as waist of EM field W ₀ = 0.05m, initial stochastic phase of gravitational waves δ = (0.21 + n)π(n = 0,1,2...). Furthermore the interference of the background transverse photon fluxes can be removed completely through establishing a suitable wave impedance function.     

An Analysis of Charged Anisotropic Star with de Sitter Spacetime

We propose a model for charged anisotropic star in de Sitter spacetime. We have taken Krori and Barua (J. Phys. A, Math. Gen. 8, 508, 1975) metric in de Sitter spacetime with non-zero cosmological constant. The model is free from singularity. We incorporate the existence of the cosmological constant on a small scale to study the structure of anisotropic charged star. To solve the Einstein-Maxwell field equations we assume the relation between the radial and transverse pressure as p _t ?p _r =g q(r)² r ² (where g is a non-zero positive constant). The physical conditions inside the stellar model are also discussed.     

Level-crossing-Untersuchung der Hyperfeinstruktur des 3d 10 4p 2 P 3/2-Terms von Cu63 und Cu65

The level-crossing technic has been used to investigate the hyperfinestructur of the 3d ¹⁰ 4p ² P _3/2-term in Copper I by scattering the resonance line λ=3248 Å on an atomic beam of separated isotop Cu⁶³ respectively Cu⁶⁵ in an external magnetic field. From the level-crossing signals values for the magnetic dipol interaction constantsA and for the electric quadrupol interaction constantsB are deduced to beeA(Cu⁶³)=(194,72±0,15) Mc/secB(Cu⁶³)=?(28,8±0,6) Mc/secA(Cu⁶⁵)=(208,57±0,15) Mc/secB(Cu⁶⁵)=?(25,9±0,6) Mc/sec. With theA-value of the 3d ¹⁰ 4p²P_1/2-term from optical measurements the ratioA(² P _3/2)∶A(² P _1/2)≈0,4 is about twice greater than for an unperturbetalkali-like²P-term. From the width of the level-crossing signals a mean lifetime of the 3d¹⁰ 4p²P_3/2-term τ=(7,0±0,2) · 10^?9 sec is deduced.