Dissipation through spin Coulomb drag in electronic spin dynamics

Spin Coulomb drag (SCD) constitutes an intrinsic source of dissipation for spin currents in metals and semiconductors. We discuss the power loss due to SCD in potential spintronics devices and analyze in detail the associated damping of collective spin-density excitations. It is found that SCD contributes substantially to the linewidth of intersubband spin plasmons in parabolic quantum wells, which suggests the possibility of a purely optical quantitative measurement of the SCD effect by means of inelastic light scattering

Dissipation through spin Coulomb drag in electronic spin transport and optical excitations

Spin Coulomb drag (SCD) constitutes an intrinsic source of dissipation for spin currents in metals and semiconductors. We discuss the power loss due to SCD in potential spintronics devices and analyze in detail the associated damping of collective spin-density excitations. It is found that SCD contributes substantially to the linewidth of intersubband spin plasmons in semiconductor quantum wells, which suggests the possibility of a purely optical quantitative measurement of the SCD effect in a parabolic well through inelastic light scattering

Intersubband spin-orbit coupling and spin splitting in symmetric quantum wells

In semiconductors with inversion asymmetry, spin-orbit coupling gives rise to the well-known Dresselhaus and Rashba effects. If one considers quantum wells with two or more conduction subbands, an additional, intersubband-induced spin-orbit term appears whose strength is comparable to the Rashba coupling, and which remains finite for symmetric structures. We show that the conduction band spin splitting due to this intersubband spin-orbit coupling term is negligible for typical III-V quantum wells

Nonuniqueness in spin-density-functional theory on lattices

In electronic many-particle systems, the mapping between densities and spin magnetizations, {n(r), m(r)}, and potentials and magnetic fields, {v(r), B(r)}, is known to be nonunique, which has fundamental and practical implications for spin-density-functional theory (SDFT). This paper studies the nonuniqueness (NU) in SDFT on arbitrary lattices. Two new, non-trivial cases are discovered, here called local saturation and global noncollinear NU, and their properties are discussed and illustrated. In the continuum limit, only some well-known special cases of NU survive.Comment: 4 pages, 1 figur

Non-adiabatic electron dynamics in time-dependent density-functional theory

Time-dependent density-functional theory (TDDFT) treats dynamical exchange and correlation (xc) via a single-particle potential, Vxc(r,t), defined as a nonlocal functional of the density n(r',t'). The popular adiabatic local-density approximation (ALDA) for Vxc(r,t) uses only densities at the same space-time point (r,t). To go beyond the ALDA, two local approximations have been proposed based on quantum hydrodynamics and elasticity theory: (a) using the current as basic variable (C-TDDFT) [G. Vignale, C. A. Ullrich, and S. Conti, Phys. Rev. Lett. 79, 4878 (1997)], (b) working in a co-moving Lagrangian reference frame (L-TDDFT) [I. V. Tokatly, Phys. Rev. B 71, 165105 (2005)]. This paper illustrates, compares, and analyzes both non-adiabatic theories for simple time-dependent model densities in the linear and nonlinear regime, for a broad range of time and frequency scales. C- and L-TDDFT are identical in certain limits, but in general exhibit qualitative and quantitative differences in their respective treatment of elastic and dissipative electron dynamics. In situations where the electronic density rapidly undergoes large deformations, it is found that non-adiabatic effects can become significant, causing the ALDA to break down.Comment: 15 pages, 15 figure

Time-dependent density functional theory on a lattice

A time-dependent density functional theory (TDDFT) for a quantum many-body system on a lattice is formulated rigorously. We prove the uniqueness of the density-to-potential mapping and demonstrate that a given density is $v$-representable if the initial many-body state and the density satisfy certain well defined conditions. In particular, we show that for a system evolving from its ground state any density with a continuous second time derivative is $v$-representable and therefore the lattice TDDFT is guaranteed to exist. The TDDFT existence and uniqueness theorem is valid for any connected lattice, independently of its size, geometry and/or spatial dimensionality. The general statements of the existence theorem are illustrated on a pedagogical exactly solvable example which displays all details and subtleties of the proof in a transparent form. In conclusion we briefly discuss remaining open problems and directions for a future research.Comment: 12 pages, 1 figur

Inhibition of crown gall induction by Agrobacterium vitis strain F2/5 in grapevine and Ricinus

Biological control measures to prevent or reduce Agrobacterium vitis-caused losses in grapevine cultures are a worldwide increasing challenge. In the present study, tumour development in grapevine (Vitis vinifera L.) was induced in the sensitive cv. Kerner by infection with Agrobacterium vitis strain K306, carrying the p35Sgus-int plasmid with the gus gene as marker for transformation by the wild-type T-DNA. Pre-inoculation with the non-tumorigenic A. vitis strain F2/5 prevented tumour induction by K306(p35gus-int). Strain M1154, a Tn5 mutant of F2/5 in the luxR-like aviR gene, partially reduced the biocontrol efficiency compared to the wild-type F2/5. GUS-labelling by K306gus was poor in grapevine in contrast to A. tumefaciens 281(p35gus-int)-induced tumours in Arabidopsis, indicating plant species-dependent variable gus expression. To use the more reliable direct mRNA expression assay by RTPCR, a new experimental plant/A. vitis system was established with Ricinus communis as model plant. Ricinus/A. vitis galls were available within one week after K306gus inoculation, reached diameters up to 5 cm, and contained more abundant GUS staining. An additional transformation marker, mRNA expression of the T-DNA-located iaaM oncogene, coding auxin synthesis, was apparent only in tumours induced by the wild-type A. vitis strain K306 in the absence of the gus construct, which is under the control of the strong 35S CaMV promoter. F2/5 pre-inoculation suppressed GUS staining and gus mRNA expression. DAPI staining revealed the loss of vital fluorescent cell nuclei in F2/5-inoculated grapevine tissue and thus inhibition of any successful T-DNA transfer into host cell nuclei. Differentiation of typical circular vessels in globular vascular bundles in M1154-pretreated galls suggests interference with plant auxin metabolism. In conclusion, together with successfully establishing a new experimental model system, Ricinus/A. vitis, pre-treatment of host tissue with the non-pathogenic strain F2/5 resulted in preventing the integration and expression of the oncogenic T-DNA of A. vitis strains by locally necrotizing host cell nuclei.

C60_{60} in intense femtosecond laser pulses: nonlinear dipole response and ionization

We study the interaction of strong femtosecond laser pulses with the C$_{60}$ molecule employing time-dependent density functional theory with the ionic background treated in a jellium approximation. The laser intensities considered are below the threshold of strong fragmentation but too high for perturbative treatments such as linear response. The nonlinear response of the model to excitations by short pulses of frequencies up to 45eV is presented and analyzed with the help of Kohn-Sham orbital resolved dipole spectra. In femtosecond laser pulses of 800nm wavelength ionization is found to occur multiphoton-like rather than via excitation of a ``giant'' resonance.Comment: 14 pages, including 1 table, 5 figure

Reentrant Superconductivity and Superconducting Critical Temperature Oscillations in F/S/F trilayers of Cu41Ni59/Nb/Cu41Ni59 Grown on Cobalt Oxide

Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers constitute the core of a superconducting spin valve. The switching effect of the spin valve is based on interference phenomena occurring due to the proximity effect at the S/F interfaces. A remarkable effect is only expected if the core structure exhibits strong critical temperature oscillations, or most favorable, reentrant superconductivity, when the thickness of the ferromagnetic layer is increased. The core structure has to be grown on an antiferromagnetic oxide layer (or such layer to be placed on top) to pin by exchange bias the magnetization-orientation of one of the ferromagnetic layers. In the present paper we demonstrate that this is possible, keeping the superconducting behavior of the core structure undisturbed.Comment: 22 pages, 12 figures, 1 tabl

Anisotropic spin-orbit induced splitting of intersubband spin plasmons

The anisotropic splitting of intersubband spin plasmons, resulting from spin-orbit coupling, is studied by angle-resolved inelastic light scattering on a [001]-oriented GaAs/AlGaAs quantum well. Confirming theoretical predictions made in [C. A. Ullrich and M. A. Flatte, Phys. Rev. B ´ 68, 235310 (2003)], this splitting is proven to exhibit a characteristic two-fold symmetry with the in-plane orientation, and to increase with increasing modulus of the excitation momentum. This opens the way to a more complete investigation, aiming at evidencing the existence of a collective spin-orbit field driving these excitations.Fil: Baboux, F.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Perez, F. Universite de Paris Vi. Institut Des Nanosciences de Paris; Francia. Centre National de la Recherche Scientifique; FranciaFil: Ullrich, C. A. . University Of Missouri; Estados UnidosFil: D'Amico, I. . University Of York; Reino UnidoFil: Gomez, Javier Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centre National de la Recherche Scientifique; Francia. Universite de Paris Vi. Institut Des Nanosciences de Paris; FranciaFil: Bernard, M.. Universite de Paris Vi. Institut Des Nanosciences de Paris; Franci