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The Dresselhaus spin-orbit interaction is quantitatively investigated in a (110)-oriented GaAs quantum well by means of time- and spatially resolved Kerr rotation. The experimental results directly demonstrate a unidirectional out-of-plane spin-orbit interaction that linearly depends on the electron momentum along the [110] direction and vanishes for the electron momentum along the [001] direction. Spatially resolved measurements of the diffusion-driven spin precession dynamics provide evidence of the formation of a persistent spin-helix state in this system. [ABSTRACT FROM AUTHOR]

The magnetization dynamics induced by a pulsed magnetic field is investigated by time- and polarization-resolved photoluminescene measurements in (Cd,Mn)Te/(Cd,Mg)Te quantum wells. The magnetization dynamics of Mn2+ ions is found to be strongly dependent on the external static magnetic field. A dynamical response of the magnetization on a subnanosecond time scale is observed at zero static magnetic field, while it drastically slows down and approaches the spin-lattice relaxation time constant for a nonzero static field. Theoretical calculations emphasize the importance of local spin interactions that interplay with the Zeeman interaction for the observed magnetization dynamics. [ABSTRACT FROM AUTHOR]

The dynamics of optically detected nuclear magnetic resonance is studied in n-GaAs via time-resolved Kerr rotation using an on-chip microcoil for rf field generation. Both optically allowed and optically forbidden NMR are observed with a dynamics controlled by the interplay between dynamic nuclear polarization via hyperfine interaction with optically generated spin-polarized electrons and nuclear spin depolarization due to magnetic resonance absorption. Comparing the characteristic nuclear spin relaxation rate obtained in experiment with master equation simulations, the underlying nuclear spin depolarization mechanism for each resonance is extracted. [ABSTRACT FROM AUTHOR]

We implemented a variation after projection (VAP) algorithm based on a triaxially deformed Hartree-Fock- Bogoliubov vacuum state. This is the first projected mean field study that includes all the quantum numbers (except parity), i.e., spin (J), isospin (T), and mass number (A). Systematic VAP calculations with JTA projection have been performed for the even-even¿/-shell nuclei with the USDB Hamiltonian. All the VAP ground state energies are within 500 keV above the exact shell model values. Our VAP calculations show that the spin projection has two important effects: (1) the spin projection is crucial in achieving good approximation of the full shell model calculation; (2) the intrinsic shapes of the VAP wave functions with spin projection are always triaxial, while the Hartree-Fock-Bogoliubov methods likely provide axial intrinsic shapes. Finally, our analysis suggests that one may not be possible to associate an intrinsic shape to an exact shell model wave function. [ABSTRACT FROM AUTHOR]

The backbending phenomenon in 48Cr has been investigated using the recently developed projected configuration interaction (PCI) method, in which the deformed intrinsic states are directly associated with shell model wave functions. Two previous explanations, (i) K=0 band crossing and (ii) K=2 band crossing, have been reinvestigated using PCI, and it was found that both explanations can successfully reproduce the experimental backbending. The PCI wave functions in the pictures of K=0 band crossing and K=2 band crossing are highly overlapped. We conclude that there are no unique intrinsic states associated with the yrast states after backbending in 48Cr. [ABSTRACT FROM AUTHOR]

Lifetimes of the yrast states in 180Pt have been measured from 4+ to 8+ using the recoil distance Doppler-shift technique in the coincidence mode. These states were populated by the reaction 156Gd(28Si,4n)180Pt at a beam energy of 144 MeV. The differential decay curve method was applied to determine the lifetimes from experimental coincidence data. The B(E2) values extracted from lifetimes increase with increasing spin, implying rotor behavior, but do not show the typical shape coexistence where the B(E2) values present a rapid increase at very low spins. Calculations based on the triaxial projected shell model were performed for the yrast states in 180Pt and the results of both energies and E2 transition probabilities reproduce the experimental data very well. The result also shows that a better description of the yrast band in 180Pt requires consideration of the γ degree of freedom. [ABSTRACT FROM AUTHOR]

In the standard Big-Bang nucleosynthesis (BBN) model, the primordial 7Li abundance is overestimated by about a factor of 2 to 3 compared to astronomical observations; this is the so-called pending cosmological lithium problem. The 7Be(n,α)4He reaction was regarded as the secondary important reaction in affecting the 7Li abundance by destructing the 7Be nucleus in BBN. However, the reaction rate of 7Be(n,α)4He has not been well studied so far. This reaction rate was first estimated by Wagoner in 1969, which has been primarily adopted in the current BBN simulations. This simple estimate involved only a direct reaction contribution, but the resonant component should also be considered according to the later experimental results. In the present work, we revised this rate based on the indirect cross-section data available for the 4He(α,n)7Be and 4He(α,p)7Li reactions by applying the charge symmetry and the principle of detailed balance. Our new result shows that the previous rate (acting as an upper limit) is overestimated by about a factor of ten. The BBN simulation shows that the present rate leads to a 1.2% increase in the final 7Li abundance compared with the result using the Wagoner rate and, hence, the present rate even worsens the 7Li problem. By the present estimation, the role of 7Be(n,α)4He in destroying 7Be is weakened from the second most importance to the third and, in turn, the 7Be(d,p)24He reaction becomes of secondary importance in destroying 7Be. [ABSTRACT FROM AUTHOR]

Two magnetic ordering transitions are found in InMnO3, the paramagnetic to antiferromagnetic transition at ~118 K and a lower possible spin rotation transition near 42 K. Multiple length scale structural measurements reveal enhanced local distortion found to be connected with tilting of the MnOs polyhedra as temperature is reduced. Coupling is observed between the lattice and the spin manifested as changes in the structure near both of the magnetic ordering temperatures (at ~4 2 and ~118 K). External parameters, such as pressure, are expected to modify the coupling. [ABSTRACT FROM AUTHOR]

The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The 12N(p, γ)130 reaction is an important branching point in the rap processes, which are believed to be alternative paths to the slow 3a process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angular distribution of the 2H(12N, 130)n proton transfer reaction at Ec.m. = 8.4 MeV has been measured for the first time. Based on the Johnson-Soper approach, the square of the asymptotic normalization coefficient (ANC) for the virtual decay of 13Og s. --> 12N 4- p was extracted to be 3.92 ± 1.47 fm-' from the measured angular distribution and utilized to compute the direct component in the 12N(p, γ)130 reaction. The direct astrophysical S factor at zero energy was then found to be 0.39 ±0.15 keV b. By considering the direct capture into the ground state of 130, the resonant capture via the first excited state of 130 and their interference, we determined the total astrophysical S factors and rates of the 12N(p, γ130 reaction. The new rate is two orders of magnitude slower than that from the REACLIB compilation. Our reaction network calculations with the present rate imply that 12N(p, γ)130 will only compete successfully with the ß+ decay of 12N at higher (~2 orders of magnitude) densities than initially predicted. [ABSTRACT FROM AUTHOR]

High-spin states in 126I have been investigated by using in-beam γ-ray spectroscopy with the 124Sn(7Li, 5n)126I reaction at a beam energy of 48 MeV. The level scheme of 126I has been extended and modified considerably by adding about 80 new γ rays and establishing five new bands. The configurations have been tentatively assigned for the yrast, yrare, and other excited bands with the help of triaxial projected shell-model (TPSM) and cranked shell-model calculations. The first band crossing in the yrast band is found due to alignments of a pair of (h11/2)² neutrons. The first and the second band crossings in the yrare band are caused by the alignments of a pair of (d5/2)² protons and a pair of (h11/2)² neutrons, respectively. Due to the successive excitations of two, four, and six quasiparticles, the alignments in the yrare band present a gigantic rising feature. The yrast band exhibits a signature inversion at low spins and becomes normal after a reversion spin of lrev = 14. The yrare band exhibits an abnormal signature inversion in which the signature inversion phase persists up to the highest spin. The signature inversions in 126I are well reproduced and successfully interpreted by the TPSM calculations. Some features of chirality are found for the four-quasiparticle (4qp) part of the yrast band and the 4qp excited band 2. [ABSTRACT FROM AUTHOR]

High-spin excited states in the very neutron-rich nucleus 114Rh have been studied by examining the prompt γ rays emitted in the spontaneous fission of 252Cf with the Gammasphere detector array. A high-spin level scheme of 114Rh has been established for the first time with 13 new levels. The level scheme is proposed to be built on a 7- state. The existence of a relatively large signature splitting and an yrare band show features which may indicate triaxial deformation. The phenomenon of signature inversion has been observed in 114Rh at I = 12 ħ. The observed signature inversion of 114Rh is interpreted successfully in terms of the triaxial projected shell model. Theoretical calculations suggest that the negative-parity, yrast band of 114Rh has the two-quasi-particle configuration of πg9/2 ⊗ νh11/2, consistent with the systematics of odd-odd Rh isotopes. The signature inversion at spin 12 ħ may be attributed to the change of rotational mode, from quasi-particle aligned rotation at low spins to collective rotation at high spins. [ABSTRACT FROM AUTHOR]

We present a novel and simple algorithm in the variation after projection (VAP) approach for the non-yrast nuclear states. It is the first time that the yrast state and non-yrast states can be varied on the same footing. The orthogonality among the calculated states is automatically fulfilled by solving the Hill-Wheeler equation. This avoids the complexity of the frequently used Gram-Schmidt orthogonalization, as adopted by the excited VAMPIR method. Thanks to Cauchy's interlacing theorem in matrix theory, the sum of the calculated lowest projected energies with the same quantum numbers can be safely minimized. Once such minimization is converged, all the calculated energies and corresponding states can be obtained, simultaneously. The present VAP calculations are performed with time-odd Hartree-Fock Slater determinants. It is shown that the calculated VAP energies (both yrast and non-yrast) are very close to the corresponding ones from the full shell model calculations. It appears the present algorithm is not limited to the VAP, but should be universal, i.e., one can do the variation with different forms of the many-body wave functions to calculate the excited states in different quantum many-body systems. [ABSTRACT FROM AUTHOR]

Fabrication of highly mobile spin-polarized two-dimensional electron gas (2DEG) is crucially important for both fundamental and applied research. Usually, spin polarization appears below 10 K for the 2DEG of LaAlO3/SrTiO3 interface, stemming from the magnetic ordering of Ti3+ ions with the mediation of itinerant electrons. Herein, we report a magnetic 2DEG at a La7/8Sr1/8MnO3-buffered LaAlO3/SrTiO3 interface, which simultaneously shows electrically tunable anomalous Hall effect and high conductivity. The spin-polarized temperature for the 2DEG is promoted to 30 K while the mobility remains high. The magnetism likely results from a gradient manganese interdiffusion into SrTiO3. The present work demonstrates the great potential of manganite-buffered LaAlO3/SrTiO3 interfaces for spintronic applications. [ABSTRACT FROM AUTHOR]

We have implemented a new variation-after-projection (VAP) calculation based on a time-odd Hartree-Fock (HF) mean field. The exact Hessian matrix of the projected energy has been successively evaluated for the first time, which makes the VAP calculation much more stable. With the time-odd mean field, the present VAP can be applied to the yrast states not only in the even-even nuclei, but also in the odd-A and odd-odd ones. The VAP energies throughout all spins for some calculated sd-shell nuclei are very close to the corresponding shell model ones. Our calculations clearly show that the spin projection is very important in achieving a good approximation to the full shell model. [ABSTRACT FROM AUTHOR]

The relative γ-decay probability ratios of the neutron resonance states in 94Zr and 92Zr populated via two-neutron transfer reactions, 92Zr(18O,16O)94Zr and 90Zr(18O,16O)92Zr, have been measured to test the validity of the surrogate ratio method (SRM) in determining the (n, γ) reaction cross section. The cross sections of the 93Zr(n,γ)94Zr reaction are derived from the experimentally obtained ratios and the cross sections of the 91Zr(n,γ)92Zr reaction in the equivalent neutron energy range of En=0-8MeV. The deduced cross sections of 93Zr(n,γ)94Zr reaction agree with the directly measured ones in the low-energy region, and with the evaluated ENDF/B-VII.1 data at higher energies of En>3MeV. The agreement supports the concept of the SRM method to indirectly determine the (n,γ) reaction cross sections. [ABSTRACT FROM AUTHOR]

Production of a monoenergetic electron bunch in a self-injected laser-wakefield accelerator is investigated with a tomographic method which resolves the electron injection and acceleration processes. It is found that all the electrons in the monoenergetic electron bunch are injected at the same location in the plasma column and then accelerated with an acceleration gradient exceeding 2 GeV/cm. The injection position shifts with the position of pump-pulse focus, and no significant deceleration is observed for the monoenergetic electron bunch after it reaches the maximum energy. The results are consistent with the model of transverse wave breaking and beam loading for the injection of monoenergetic electrons. The tomographic method adds a crucial dimension to the whole array of existing diagnostics for laser beams, plasma waves, and electron beams. With this method the details of the underlying physical processes in laser-plasma interactions can be resolved and compared directly to particle-in-cell simulations.

A tomographic diagnosis method was developed to systematically resolve the injection and acceleration processes of a monoenergetic electron beam in a laser-wakefield accelerator. It was found that all the monoenergetic electrons are injected at the same location in the plasma column and accelerated from 5 to 55 MeV energy in 200 microm distance. This is a direct measurement of the real acceleration gradient in a laser-wakefield accelerator, and the experimental data are consistent with the model of transverse wave breaking and beam loading for monoenergetic electron injection.