PubMed Health⌕ Search

Biomedical subjects

Igor V Ovchinnikov

Publications and source records attributed to Igor V Ovchinnikov.

7 recordsLinked to original sources
PubMed2007

Nonlinear signal mixing in a three-terminal molecular wire.

The authors study the electronic response of two simple molecular devices to a bichromatic field, where the device acts as a mixer. Two closely related model systems are considered: one is a benzene molecule and the other is a single grapheme sheet, and in both cases the systems are connected to three polyacetylene chains. The electronic response to the dichromatic alternating electric fields is studied by following the electron density fluctuation along the chain lengths. In both cases the electron transfer follows the field frequency at low electric fields. At higher amplitude, a significant amount of nonlinear mixing resulting in new combinations of the input frequencies is found in the spectrum. The influence of gating on the output frequencies is also shown.

Journal Article↗
PubMed2006

Orbital-free tensor density functional theory.

We propose a family of time-dependent orbital-free density-based theories that go beyond the usual current-density description of electrons or other particles. The theories deal with physical quantities that characterize the one-particle density matrix and consequently the kinetics of the particles. We analyze the first two theories in the family. The "lowest-order" theory is quantum hydrodynamics. The second one yields not only the longitudinal plasmon collective excitations, but also the transverse phonon modes that are associated with elementary excitations in Fermi liquids. The theories should make it feasible to do large orbital-free simulations of time-dependent and stationary systems.

Journal Article↗
PubMed2005

Spintronics birefringence with an extended molecular loop-wire or spiral coupling.

A ring with spin-orbit effects coupled to a conducting wire is shown to exhibit a phase delay which is spin dependent. The key is that the coupling of the ring to the wire is over an extended spatial range and not just along a single point; this breaks the symmetry and makes the ring states couple differently to forward and backward moving wire states. This results, for properly injected spin states, in a spin-flipping probability which is dependent on the energy of the injected electron and can therefore be easily controlled. Several systems are presented and shown to exhibit this effect including the basic ring which couples to a wire as well as a ring which mediates between two wires, and a spiral between two wires.

Journal Article↗
PubMed2005

Conductivity and gating of silicon ringchains.

One-dimensional and two-dimensional conductivity calculations are done for a set of several closely spaced quantum silicon rings, following the development of bottom-up approaches for producing silicon rings. The transmission is easily influenced by electric and magnetic gatings and has band features even for two or three rings, showing its potential usefulness for logical devices. Analysis on different gatings shows that the electric-field gating would be as effective as the Aharonov-Bohm magnetic gating.

Journal Article↗
PubMed2005

Finite bias conductance of an Anderson level: a source--Liouville Hartree-Fock study.

We address the problem of stationary conductance through an Anderson spin-degenerate level at finite bias. Just as in the Anderson solution, for a finite bias in parameter space (bias, gate voltage, interaction constant, and the couplings to the leads) there exist spin-polarized and non-spin-polarized regions. The transition curve between them is found analytically for the case of symmetric coupling to the left and right leads. We approach the problem by a non-Markovian source-Liouville equation where the two-body interaction self-energies are taken in the Hartree-Fock approximation.

Journal Article↗
PubMed2005

A Liouville equation for systems which exchange particles with reservoirs: transport through a nanodevice.

A Redfield-like Liouville equation for an open system that couples to one or more leads and exchanges particles with them is derived. The equation is presented for a general case. A case study of time-dependent transport through a single quantum level for varying electrostatic and chemical potentials in the leads is presented. For the case of varying electrostatic potentials the proposed equation yields, for the model study, the results of an exact solution.

Computer Simulation↗