199 research outputs found
Time-dependent single electron tunneling through a shuttling nano-island
We offer a general approach to calculation of single-electron tunneling
spectra and conductance of a shuttle oscillating between two half-metallic
leads with fully spin polarized carriers. In this case the spin-flip processes
are completely suppressed and the problem may be solved by means of canonical
transformation, where the adiabatic component of the tunnel transparency is
found exactly, whereas the non-adiabatic corrections can be taken into account
perturbatively. Time-dependent corrections to the tunnel conductance of moving
shuttle become noticeable at finite bias in the vicinity of the even/odd
occupation boundary at the Coulomb diamond diagram.Comment: 12 pages, 4 figure
The model of drying sessile drop of colloidal solution
We have proposed and investigated a model of drying colloidal suspension drop
placed onto a horizontal substrate in which the sol to gel phase transition
occurs. The temporal evolution of volume fraction of the solute and the gel
phase dynamics were obtained from numerical simulations. Our model takes into
account the fact that some physical quantities are dependent on volume fraction
of the colloidal particles.Comment: Submitted to IJMP
Electron-hole asymmetry is the key to superconductivity
In a solid, transport of electricity can occur via negative electrons or via
positive holes. In the normal state of superconducting materials experiments
show that transport is usually dominated by
. Instead, in the superconducting state experiments show that the
supercurrent is always carried by .
These experimental facts indicate that electron-hole asymmetry plays a
fundamental role in superconductivity, as proposed by the theory of hole
superconductivity.Comment: Presented at the New3SC-4 meeting, San Diego, Jan. 16-21 2003; to be
published in Int. J. Mod. Phys.
Magnetic field induced two-channel Kondo effect in multiple quantum dots
We study the possibility to observe the two channel Kondo physics in multiple
quantum dot heterostructures in the presence of magnetic field. We show that a
fine tuning of the coupling parameters of the system and an external magnetic
field may stabilize the two channel Kondo critical point. We make predictions
for behavior of the scaling of the differential conductance in the vicinity of
the quantum critical point, as a function of magnetic field, temperature and
source-drain potential.Comment: 7 pages, 3 figure
Why holes are not like electrons. II. The role of the electron-ion interaction
In recent work, we discussed the difference between electrons and holes in
energy band in solids from a many-particle point of view, originating in the
electron-electron interaction, and argued that it has fundamental consequences
for superconductivity. Here we discuss the fact that there is also a
fundamental difference between electrons and holes already at the single
particle level, arising from the electron-ion interaction. The difference
between electrons and holes due to this effect parallels the difference due to
electron-electron interactions: {\it holes are more dressed than electrons}. We
propose that superconductivity originates in 'undressing' of carriers from
electron-electron and electron-ion interactions, and that both aspects
of undressing have observable consequences.Comment: Continuation of Phys.Rev.B65, 184502 (2002) = cond-mat/0109385 (2001
Vibration-induced Kondo tunneling through metal-organic complexes with even electron occupation number
We investigate transport through a mononuclear transition-metal complex with
strong tunnel coupling to two electrodes. The ground state of this molecule is
a singlet while the first excited state is a triplet. We show that a modulation
of the tunnel-barrier due to a molecular distortion which couples to the
tunneling induces a Kondo-effect, provided the discrete vibrational energy
compensates the singlet/triplet gap. We discuss the single-phonon and
two-phonon assisted co-tunneling and possible experimental realization of the
theory.Comment: 4 pages, 3 eps figure
Interplay between Heavy Fermions and Crystal Field Excitation in Kondo Lattices. Low-Temperature Thermodynamics and Inelastic Neutron Scattering Spectra of CeNiSn
The microscopic theory of interaction between the heavy fermions and the
crystal field excitations in Kondo lattices is presented. It is shown that the
heavy-fermion spectrum scaled by the Kondo temperature can be modified by
the crystal field excitations with the energy provided the
inequality is realized. On the base of general description of
excitation spectrum the detailed qualitative and quantitative explanation of
anisotropic inelastic neutron scattering spectra and low-temperature specific
heat of orthorhombic CeNiSn is given. The theory resolves the apparent
contradiction between the metallic conductivity and the gap-wise behavior of
thermodynamic properties and spin response of CeNiSn at low temperatures.Comment: 24 pages (LaTeX), 12 Postscript figures, submitted to Phys.Rev.
Electron self-trapping in intermediate-valent SmB6
SmB6 exhibits intermediate valence in the ground state and unusual behaviour
at low temperatures. The resistivity and the Hall effect cannot be explained
either by conventional sf-hybridization or by hopping transport in an impurity
band. At least three different energy scales determine three temperature
regimes of electron transport in this system. We consider the ground state
properties, the soft valence fluctuations and the spectrum of band carriers in
n-doped SmB6. The behaviour of excess conduction electrons in the presence of
soft valence fluctuations and the origin of the three energy scales in the
spectrum of elementary excitations is discussed. The carriers which determine
the low-temperature transport in this system are self-trapped electron-polaron
complexes rather than simply electrons in an impurity band. The mechanism of
electron trapping is the interaction with soft valence fluctuations.Comment: 12 pages, 3 figure
Shuttle-promoted nano-mechanical current switch
We investigate electron shuttling in three-terminal nanoelectromechanocal
device built on a movable metallic rod oscillating between two drains. The
device shows a double-well shaped electromechanical potential tunable by a
source-drain bias voltage. Four stationary regimes controllable by the bias are
found for this device: (i) single stable fixed point, (ii) two stable fixed
points, (iii) two limiting cycles, and (iv) single limiting cycle. In the
presence of perpendicular magnetic field the Lorentz force makes possible
switching from one electromechanical state to another. The mechanism of tunable
transitions between various stable regimes based on the interplay between
voltage controlled electromechanical instability and magnetically controlled
switching is suggested. The switching phenomenon is implemented for achieving
both a reliable \emph{active} current switch and sensoring of small variations
of magnetic field.Comment: 11 pages, 4 figure
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