1 Department of Physics, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan 2 Institute for Solid State Physics, University of Tokyo, Chiba 277-8581, Japan We study the impurity-induced phase transitions in a quasi-one-dimensional Heisenberg antiferromagnet doped with magnetic spin-1/2 impurities and non-magnetic ones. The impurity-induced transition temperature determined by...

Knowledge of the impurity transport parameters and their relation with those of the main plasma particles is important for predicting the fusion performance of a tokamak reactor and provides an element for validating advanced transport models currently under development. The radial profiles of fully ionized carbon C (transition n=8-7, 529.1 nm) released from TCV (R = 0.88 m, a<0.25m, BT<1.5 T) ...

The spin dynamics of an arbitrary localized impurity in an insulating two-dimensional antiferromagnet, across the host transition from a paramagnet with a spin gap to a Neel state, is described. The impurity spin susceptibility has a Curie-like divergence at the quantum-critical coupling, but with a universal effective spin that is neither an integer nor a half-odd integer. In the Neel state, t...

We compute the single particle inverse lifetime, evaluated in the superconducting state. Within the BCS framework, the calculation can be done nonperturbatively, i.e. poles can be found well away from the real axis. We find that perturbative calculations are in good agreement with these results, even for non-zero impurity scattering. With electron-phonon scattering added to the problem, we use ...

We investigate the nitrogen substitutional impurity in semiconducting zigzag and metallic armchair single-wall carbon nanotubes using ab initio density functional theory. At low concentrations (less than 1 at. %), the defect state in a semiconducting tube becomes spatially localized and develops a flat energy level in the band gap. Such a localized state makes the impurity site chemically and e...

Numerical procedure is developed for analyzing impurity-induced resonant-state STM images observed in high-Tc superconductors, and is applied to three sets of higher resolution data provided to us by J. C. Seamus Davis and E. W. Hudson. Each image is associated with a Zn impurity in Bi2Sr2CaCu2O8. The averaged, integrated, relative quasiparticle local density of states at all predominant CusZnd...

We report ground state energies and structural properties for small helium clusters (He) containing an H− impurity computed by means of variational and diffusion Monte Carlo methods. Except for 4He2H − that has a noticeable contribution from collinear geometries where the H− impurity lies between the two He atoms, our results show that our 4HeNH − clusters have a compact 4HeN subsystem that bin...

We present the results of a study of the energy spectrum of the ground state for shallow donors in quantum well structures, consisting of a single slab of GaAs sandwiched between two semiinfinite layers of Ga1 _ x Alx As. The effect of the position of the impurity atom within the central GaAs slab is investigated for different slab thicknesses and alloy compositions. Two limiting cases are pres...

The correspondence between the steady-state theory of current transfer and scattering theory in a system of coupled tight-binding models of one-dimensional wires is explored. For weak interwire coupling both calculations give nearly identical results, except at singular points associated with band edges. The effect of decoherence in each of these models is studied using a generalization of the ...

In this research, the effect of two process control agent: methanol (liquid state) and stearicacid (solid state) on mechanical alloying process of Ti and Al with equal at%(Ti50Al50) wereinvestigated. Phase transformation at presence of two PCA was: at first, powder mixture wastransformed to a metastable solid solution of Al in Ti lattice (disordered hcp) and then transformed toamorphous phase w...