1,530 research outputs found
The icephobic performance of alkyl-grafted aluminum surfaces
This work analyzes the anti-icing performance of flat aluminum surfaces coated with widely used alkyl-group based layers of octadecyltrimethoxysilane, fluorinated alkylsilane and stearic acid as they are subjected to repeated icing/deicing cycles. The wetting properties of the samples upon long-term immersion in water are also evaluated. The results demonstrate that smooth aluminum surfaces grafted with alkyl groups are prone to gradual degradation of their hydrophobic and icephobic properties, which is caused by interactions and reactions with both ice and liquid water. This implies that alkyl-group based monolayers on aluminum surfaces are not likely to be durable icephobic coatings unless their durability in contact with ice and/or water is significantly improved
Shuttling of Spin Polarized Electrons in Molecular Transistors
Shuttling of electrons in single-molecule transistors with magnetic leads in
the presence of an external magnetic field is considered theoretically. For a
current of partially spin-polarized electrons a shuttle instability is
predicted to occur for a finite interval of external magnetic field strengths.
The lower critical magnetic field is determined by the degree of spin
polarization and it vanishes as the spin polarization approaches 100%. The
feasibility of detecting magnetic shuttling in a -based molecular
transistor with magnetic (Ni) electrodes is discussed [A.~N.~Pasupathy et al.,
Science 306, 86 (2004)].Comment: Submitted to a special issue of "Synthetic Metals" to appear in March
201
Superconductive pumping of nanomechanical vibrations
We demonstrate that a supercurrent can pump energy from a battery that
provides a voltage bias into nanomechanical vibrations. Using a device
containing a nanowire Josephson weak link as an example we show that a
nonlinear coupling between the supercurrent and a static external magnetic
field leads to a Lorentz force that excites bending vibrations of the wire at
resonance conditions. We also demonstrate the possibility to achieve more than
one regime of stationary nonlinear vibrations and how to detect them via the
associated dc Josephson currents and we discuss possible applications of such a
multistable nanoelectromechanical dynamics.Comment: 4 pages, 5 figure
Mechanically Induced Thermal Breakdown in Magnetic Shuttle Structures
A theory of a thermally induced single-electron "shuttling" instability in a
magnetic nanomechanical device subject to an external magnetic field is
presented in the Coulomb blockade regime of electron transport. The model
magnetic shuttle device considered comprises a movable metallic grain suspended
between two magnetic leads, which are kept at different temperatures and
assumed to be fully spin polarized with antiparallel magnetizations. For a
given temperature difference shuttling is found to occur for a region of
external magnetic fields between a lower and an upper critical field strength,
which separate the shuttling regime from normal small-amplitude "vibronic"
regimes. We find that (i) the upper critical magnetic field saturates to a
constant value in the high temperature limit and that the shuttle instability
domain expands with a decrease of the temperature, (ii) the lower critical
magnetic field depends not only on the temperature independent phenomenological
friction coefficient used in the model but also on intrinsic friction (which
vanishes in the high temperature limit) caused by magnetic exchange forces and
electron tunneling between the quantum dot and the leads. The feasibility of
using thermally driven magnetic shuttle systems to harvest thermal breakdown
phenomena is discussed.Comment: 9 pages, 2 figure
Single-electron shuttle based on electron spin
A nanoelectromechanical device based on magnetic exchange forces and electron spin flips induced by a weak external magnetic field is suggested. It is shown that this device can operate as a new type of single-electron "shuttle" in the Coulomb blockade regime of electron transport
Magnetopolaronic effects in electron transport through a single-level vibrating quantum dot
Magneto-polaronic effects are considered in electron transport through a
single-level vibrating quantum dot subjected to a transverse (to the current
flow) magnetic field. It is shown that the effects are most pronounced in the
regime of sequential electron tunneling, where a polaronic blockade of the
current at low temperatures and an anomalous temperature dependence of the
magnetoconductance are predicted. In contrast, for resonant tunneling of
polarons the peak conductance is not affected by the magnetic field.Comment: 7 pages, 2 figure
Umklapp-Assisted Electron Transport Oscillations in Metal Superlattices
We consider a superlattice of parallel metal tunnel junctions with a
spatially non-homogeneous probability for electrons to tunnel. In such
structures tunneling can be accompanied by electron scattering that conserves
energy but not momentum. In the special case of a tunneling probability that
varies periodically with period in the longitudinal direction, i.e.,
perpendicular to the junctions, electron tunneling is accompanied by "umklapp"
scattering, where the longitudinal momentum changes by a multiple of . We
predict that as a result a sequence of metal-insulator transitions can be
induced by an external electric- or magnetic field as the field strength is
increased.Comment: 5 pages, 3 figure
Joule Heating and Current-Induced Instabilities in Magnetic Nanocontacts
We consider the electrical current through a magnetic point contact in the
limit of a strong inelastic scattering of electrons. In this limit local Joule
heating of the contact region plays a decisive role in determining the
transport properties of the point contact. We show that if an applied constant
bias voltage exceeds a critical value, the stationary state of the system is
unstable, and that periodic, non-harmonic oscillations in time of both the
electrical current through the contact and the local temperature in the contact
region develop spontaneously. Our estimations show that the necessary
experimental conditions for observing such oscillations with characteristic
frequencies in the range Hz can easily be met. We also show a
possibility to manipulate upon the magnetization direction of a magnetic grain
coupled through a point contact to a bulk ferromagnetic by exciting the
above-mentioned thermal-electric oscillations.Comment: 9 pages, 6 figures, submitted to Physical Review
- …