Magnetoresistance in the s-d Model with Arbitrary Impurity Spin

The magnetoresistance, the number of the localized electrons, and the s-wave scattering phase shift at the Fermi level for the s-d model with arbitrary impurity spin are obtained in the ground state. To obtain above results some known exact results of the Bethe ansatz method are used. As the impurity spin S = 1/2, our results coincide with those obtained by Ishii \textit{et al%}. The compairsion between the theoretical and experimental magneticresistence for impurity S = 1/2 is re-examined.Comment: 6 pages, 2 figure

Nonclassicality filters and quasiprobabilities

Necessary and sufficient conditions for the nonclassicality of bosonic quantum states are formulated by introducing nonclassicality filters and nonclassicality quasiprobability distributions. Regular quasiprobabilities are constructed from characteristic functions which can be directly sampled by balanced homodyne detection. Their negativities uncover the nonclassical effects of general quantum states. The method is illustrated by visualizing the nonclassical nature of a squeezed state.Comment: Significantly revised version, more emphasis on practical applicatio

On the Newtonian origin of the spin motive force in ferromagnetic atomic wires

We demonstrate numerically the existence of a spin-motive force acting on spin-carriers when moving in a time and space dependent internal field. This is the case of electrons in a one-dimensional wires with a precessing domain wall. The effect can be explained solely by considering adiabatic dynamics and it is shown to exist for both classical and quantum systems.Comment: 5 pages, 7 figures, added figure 7 and tex

Magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine molecules (M ≡\equiv Fe, Co)

We report on a theoretical study of magnetic transitions induced by tunnelling electrons in individual adsorbed M-Phthalocyanine (M-Pc) molecules where M is a metal atom: Fe-Pc on a Cu(110)(2$\times$1)-O surface and Co-Pc layers on Pb(111) islands. The magnetic transitions correspond to the change of orientation of the spin angular momentum of the metal ion with respect to the surroundings and possibly an applied magnetic field. The adsorbed Fe-Pc system is studied with a Density Functional Theory (DFT) transport approach showing that i) the magnetic structure of the Fe atom in the adsorbed Fe-Pc is quite different from that of the free Fe atom or of other adsorbed Fe systems and ii) that injection of electrons (holes) into the Fe atom in the adsorbed Fe-Pc molecule dominantly involves the Fe $3d_{z^2}$ orbital. These results fully specify the magnetic structure of the system and the process responsible for magnetic transitions. The dynamics of the magnetic transitions induced by tunnelling electrons is treated in a strong-coupling approach. The Fe-Pc treatment is extended to the Co-Pc case. The present calculations accurately reproduce the strength of the magnetic transitions as observed by magnetic IETS (Inelastic Electron Tunnelling Spectroscopy) experiments; in particular, the dominance of the inelastic current in the conduction of the adsorbed M-Pc molecule is accounted for

Defect-induced spin-glass magnetism in incommensurate spin-gap magnets

We study magnetic order induced by non-magnetic impurities in quantum paramagnets with incommensurate host spin correlations. In contrast to the well-studied commensurate case where the defect-induced magnetism is spatially disordered but non-frustrated, the present problem combines strong disorder with frustration and, consequently, leads to spin-glass order. We discuss the crossover from strong randomness in the dilute limit to more conventional glass behavior at larger doping, and numerically characterize the robust short-range order inherent to the spin-glass phase. We relate our findings to magnetic order in both BiCu2PO6 and YBa2Cu3O6.6 induced by Zn substitution.Comment: 6 pages, 5 figs, (v2) real-space RG results added; discussion extended, (v3) final version as publishe

Kondo behavior in the asymmetric Anderson model: Analytic approach

The low-temperature behavior of the asymmetric single-impurity Anderson model is studied by diagrammatic methods resulting in analytically controllable approximations. We first discuss the ways one can simplify parquet equations in critical regions of singularities in the two-particle vertex. The scale vanishing at the critical point defines the Kondo temperature at which the electron-hole correlation function saturates. We show that the Kondo temperature exists at any filling of the impurity level. A quasiparticle resonance peak in the spectral function, however, forms only in almost electron-hole symmetric situations. We relate the Kondo temperature with the width of the resonance peak. Finally we discuss the existence of satellite Hubbard bands in the spectral function.Comment: REVTeX4, 11 pages, 5 EPS figure

Verifying continuous-variable entanglement in finite spaces

Starting from arbitrary Hilbert spaces, we reduce the problem to verify entanglement of any bipartite quantum state to finite dimensional subspaces. Hence, entanglement is a finite dimensional property. A generalization for multipartite quantum states is also given.Comment: 4 page

Exchange parameters from approximate self-interaction correction scheme

The approximate atomic self-interaction corrections (ASIC) method to density functional theory is put to the test by calculating the exchange interaction for a number of prototypical materials, critical to local exchange and correlation functionals. ASIC total energy calculations are mapped onto an Heisenberg pair-wise interaction and the exchange constants J are compared to those obtained with other methods. In general the ASIC scheme drastically improves the bandstructure, which for almost all the cases investigated resemble closely available photo-emission data. In contrast the results for the exchange parameters are less satisfactory. Although ASIC performs reasonably well for systems where the magnetism originates from half-filled bands, it suffers from similar problems than those of LDA for other situations. In particular the exchange constants are still overestimated. This reflects a subtle interplay between exchange and correlation energy, not captured by the ASIC.Comment: 10 page

Entanglement of an impurity and conduction spins in the Kondo model

Based on Yosida's ground state of the single-impurity Kondo Hamiltonian, we study three kinds of entanglement between an impurity and conduction electron spins. First, it is shown that the impurity spin is maximally entangled with all the conduction electrons. Second, a two-spin density matrix of the impurity spin and one conduction electron spin is given by a Werner state. We find that the impurity spin is not entangled with one conduction electron spin even within the Kondo screening length $\xi_K$, although there is the spin-spin correlation between them. Third, we show the density matrix of two conduction electron spins is nearly same to that of a free electron gas. The single impurity does not change the entanglement structure of the conduction electrons in contrast to the dramatic change in electrical resistance.Comment: 5 pages, 2 figures, accepted for publication in Physical Review

Predictability of band-limited, high-frequency, and mixed processes in the presence of ideal low-pass filters

Pathwise predictability of continuous time processes is studied in deterministic setting. We discuss uniform prediction in some weak sense with respect to certain classes of inputs. More precisely, we study possibility of approximation of convolution integrals over future time by integrals over past time. We found that all band-limited processes are predictable in this sense, as well as high-frequency processes with zero energy at low frequencies. It follows that a process of mixed type still can be predicted if an ideal low-pass filter exists for this process.Comment: 10 page