248 research outputs found
Enhancement of spin injection from ferromagnetic metal into a two-dimensional electron gas using a tunnel barrier
Josephson effect in graphene SBS junctions
We study Josephson effect in graphene superconductor- barrier- superconductor
junctions with short and wide barriers of thickness and width , which
can be created by applying a gate voltage across the barrier region. We
show that Josephson current in such graphene junctions, in complete contrast to
their conventional counterparts, is an oscillatory function of both the barrier
width and the applied gate voltage . We also demonstrate that in the
thin barrier limit, where and keeping
finite, such an oscillatory behavior can be understood in terms of transmission
resonance of Dirac-Bogoliubov-de Gennes quasiparticles in superconducting
graphene. We discuss experimental relevance of our work.Comment: 7 Pg., 6 Figs, extended version submitted to PR
The Kondo Effect in the Presence of Magnetic Impurities
We measure transport through gold grain quantum dots fabricated using
electromigration, with magnetic impurities in the leads. A Kondo interaction is
observed between dot and leads, but the presence of magnetic impurities results
in a gate-dependent zero-bias conductance peak that is split due to an RKKY
interaction between the spin of the dot and the static spins of the impurities.
A magnetic field restores the single Kondo peak in the case of an
antiferromagnetic RKKY interaction. This system provides a new platform to
study Kondo and RKKY interactions in metals at the level of a single spin.Comment: 5 pages, 4 figure
Electron transport through single Mn12 molecular magnets
We report transport measurements through a single-molecule magnet, the Mn12
derivative [Mn12O12(O2C-C6H4-SAc)16(H2O)4], in a single-molecule transistor
geometry. Thiol groups connect the molecule to gold electrodes that are
fabricated by electromigration. Striking observations are regions of complete
current suppression and excitations of negative differential conductance on the
energy scale of the anisotropy barrier of the molecule. Transport calculations,
taking into account the high-spin ground state and magnetic excitations of the
molecule, reveal a blocking mechanism of the current involving non-degenerate
spin multiplets.Comment: Accepted for Phys. Rev. Lett., 5 pages, 4 figure
Electrical detection of spin accumulation and spin precession at room temperature in metallic spin valves
We have fabricated a multiterminal lateral mesoscopic metallic spin valve demonstrating spin precession at room temperature (RT), using tunnel barriers in combination with metallic ferromagnetic electrodes as a spin injector and detector. The observed modulation of the output signal due to the spin precession is discussed and explained in terms of a time-of-flight experiment of electrons in a diffusive conductor. The obtained spin relaxation length lambda(sf)=500 nm in an aluminum strip will make detailed studies of spin dependent transport phenomena possible and allow one to explore the possibilities of the electron spin for-new electronic applications at RT. (C) 2002 American Institute of Physics. [DOI: 10.1063/1.1532753].</p
Schetsboek windturbines & ruimtelijke kwaliteit; landschappelijk onderzoek naar vides en concentratiegebieden
Dit schetsboek voor landschapsontwerp is gemaakt door Alterra, Bosch Slabbers tuin- en landschapsarchitecten en Buro Schöne, in opdracht van VROM, DG Ruimte. Deze landschapsvisie past in het kader van het Nationaal Plan van Aanpak Windenergi
Differentiation of muscle, fat, cartilage, and bone from progenitor cells present in a bone-derived clonal cell population: effect of dexamethasone.
Tunneling conductance in strained graphene-based superconductor: Effect of asymmetric Weyl-Dirac fermions
Based on the BTK theory, we investigate the tunneling conductance in a
uniaxially strained graphene-based normal metal (NG)/ barrier
(I)/superconductor (SG) junctions. In the present model, we assume that
depositing the conventional superconductor on the top of the uniaxially
strained graphene, normal graphene may turn to superconducting graphene with
the Cooper pairs formed by the asymmetric Weyl-Dirac electrons, the massless
fermions with direction-dependent velocity. The highly asymmetrical velocity,
vy/vx>>1, may be created by strain in the zigzag direction near the transition
point between gapless and gapped graphene. In the case of the highly
asymmetrical velocity, we find that the Andreev reflection strongly depends on
the direction and the current perpendicular to the direction of strain can flow
in the junction as if there was no barrier. Also, the current parallel to the
direction of strain anomalously oscillates as a function of the gate voltage
with very high frequency. Our predicted result is found as quite different from
the feature of the quasiparticle tunneling in the unstrained graphene-based
NG/I/SG conventional junction. This is because of the presence of the
direction-dependent-velocity quasiparticles in the highly strained graphene
system.Comment: 18 pages, 7 Figures; Eq.13 and 14 are correcte
Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect
The ability to make electrical contact to single molecules creates
opportunities to examine fundamental processes governing electron flow on the
smallest possible length scales. We report experiments in which we controllably
stretch individual cobalt complexes having spin S = 1, while simultaneously
measuring current flow through the molecule. The molecule's spin states and
magnetic anisotropy were manipulated in the absence of a magnetic field by
modification of the molecular symmetry. This control enabled quantitative
studies of the underscreened Kondo effect, in which conduction electrons only
partially compensate the molecular spin. Our findings demonstrate a mechanism
of spin control in single-molecule devices and establish that they can serve as
model systems for making precision tests of correlated-electron theories.Comment: main text: 5 pages, 4 figures; supporting information attached; to
appear in Science
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