1,370 research outputs found
Vibrational Instability due to Coherent Tunneling of Electrons
Effects of a coupling between the mechanical vibrations of a quantum dot
placed between the two leads of a single electron transistor and coherent
tunneling of electrons through a single level in the dot has been studied. We
have found that for bias voltages exceeding a certain critical value a
dynamical instability occurs and mechanical vibrations of the dot develop into
a stable limit cycle. The current-voltage characteristics for such a transistor
were calculated and they seem to be in a reasonably good agreement with recent
experimental results for the single -molecule transistor by Park et
al.(Nature {\bf 407,} (2000) 57).Comment: 5 pages, 3 figure
Thermoelectrical manipulation of nanomagnets
We investigate the interplay between the thermodynamic properties and
spin-dependent transport in a mesoscopic device based on a magnetic multilayer
(F/f/F), in which two strongly ferromagnetic layers (F) are exchange-coupled
through a weakly ferromagnetic spacer (f) with the Curie temperature in the
vicinity of room temperature. We show theoretically that the Joule heating
produced by the spin-dependent current allows a spin-thermo-electronic control
of the ferromagnetic-to-paramagnetic (f/N) transition in the spacer and,
thereby, of the relative orientation of the outer F-layers in the device
(spin-thermo-electric manipulation of nanomagnets). Supporting experimental
evidence of such thermally controlled switching from parallel to antiparallel
magnetization orientations in F/f(N)/F sandwiches is presented. Furthermore, we
show theoretically that local Joule heating due to a high concentration of
current in a magnetic point contact or a nanopillar can be used to reversibly
drive the weakly ferromagnetic spacer through its Curie point and thereby
exchange couple and decouple the two strongly ferromagnetic F-layers. For the
devices designed to have an antiparallel ground state above the Curie point of
the spacer, the associated spin-thermionic parallel-to-antiparallel switching
causes magneto-resistance oscillations whose frequency can be controlled by
proper biasing from essentially DC to GHz. We discuss in detail an experimental
realization of a device that can operate as a thermo-magneto-resistive switch
or oscillator.Comment: This paper, published in J. Appl. Phys. 107, 123706 (2010), is an
expanded version of arXiv:0710.5477 (8 pages, 12 figures, two additional
authors and experimental section added
DC spin generation by junctions with AC driven spin-orbit interaction
An unbiased one-dimensional weak link between two terminals, subjected to the
Rashba spin-orbit interaction caused by an AC electric field which rotates
periodically in the plane perpendicular to the link, is shown to inject
spin-polarized electrons into the terminals. The injected spin-polarization has
a DC component along the link and a rotating transverse component in the
perpendicular plane. In the adiabatic, low rotation-frequency regime, these
polarization components are proportional to the frequency. The DC component of
the polarization vanishes for a linearly-polarized electric field.Comment: published versio
Spintronics of a Nanoelectromechanical Shuttle
We consider effects of the spin degree of freedom on the nanomechanics of a
single-electron transistor (SET) containing a nanometer-sized metallic cluster
suspended between two magnetic leads. It is shown that in such a
nanoelectromechanical SET(NEM-SET) the onset of an electromechanical
instability leading to cluster vibrations and "shuttle" transport of electrons
between the leads can be controlled by an external magnetic field. Different
stable regimes of this spintronic NEM-SET operation are analyzed. Two different
scenarios for the onset of shuttle vibrations are found.Comment: 4 pages, 3 figure
Quantum Shuttle Phenomena in a Nanoelectromechanical Single-Electron Transistor
An analytical analysis of quantum shuttle phenomena in a
nanoelectromechanical single-electron transistor has been performed in the
realistic case, when the electron tunnelling length is much greater than the
amplitude of the zero point oscillations of the central island. It is shown
that when the dissipation is below a certain threshold value, the vibrational
ground state of the central island is unstable. The steady-state into which
this instability develops is studied. It is found that if the electric field
between the leads is much greater than a characteristic value , the quasiclassical shuttle picture is recovered, while if a new quantum regime of shuttle vibrations occurs. We show
that in the latter regime small quantum fluctuations result in large (i.e.
finite in the limit ) shuttle vibrations.Comment: 5 pages, 1 figur
Spin-thermo-electronic oscillator based on inverse giant magnetoresistance
A spin-thermo-electronic valve with the free layer of exchange-spring type
and inverse magnetoresistance is investigated. The structure has S-shaped
current-voltage characteristics and can exhibit spontaneous oscillations when
integrated with a conventional capacitor within a resonator circuit. The
frequency of the oscillations can be controlled from essentially dc to the GHz
range by the circuit capacitance.Comment: 7 pages, 9 figure
Electrical Manipulation of Nanomagnets
We demonstrate a possibility to manipulate the magnetic coupling between two
nanomagnets with a help of ac electric field. In the scheme suggested the
magnetic coupling in question is mediated by a magnetic particle contacting
with both of the nanomagnets through the tunnel barriers. The electric field
providing a successive suppression of the barriers leads to pumping of
magnetization through the mediating particle. Time dependent dynamics of the
particle magnetization allows to to switch between ferro- and antiferromagnetic
couplings.Comment: 4 pages, 2 figure
Mechanical Cooper pair transportation as a source of long distance superconducting phase coherence
Transportation of Cooper-pairs by a movable single Cooper-pair-box placed
between two remote superconductors is shown to establish coherent coupling
between them. This coupling is due to entanglement of the movable box with the
leads and is manifested in the supression of quantum fluctuations of the
relative phase of the order parameters of the leads. It can be probed by
attaching a high resistance Josephson junction between the leads and measuring
the current through this junction. The current is suppressed with increasing
temperature.Comment: 4 pages, 4 figures, RevTeX; Updated version, typos correcte
Quantum Spin Fluctuations as a Source of Long-Range Proximity Effects in Diffusive Ferromagnet-Superconductor Structures
We show that quantum spin fluctuations in inhomogeneous ferromagnets
drastically affect the Andreev reflection of electrons and holes at a
ferromagnet-superconductor interface. As a result a strong long-range proximity
effect appears, associated with electron-hole spin triplet correlations and
persisting on a lenght scale typical for non-magnetic materials, but
anomalously large for ferromagnets.Comment: 4 pages, 2 figure
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