4,393 research outputs found
Optical bistability and hysteresis of hybrid metal-semiconductor nano-dimer
Optical response of an artificial composite nano-dimer comprising a
semiconductor quantum dot and a metal nanosphere is analyzed theoretically. We
show that internal degrees of freedom of the system can manifest bistability
and optical hysteresis as functions of the incident field intensity. We argue
that these effects can be observed for the real world systems, such as a CdSe
quantum dot and an Au nanoparticle hybrids. These properties can be revealed by
measuring the optical hysteresis of the Rayleigh scattering. We show also that
the total dipole moment of the system can be switched abruptly between its two
stable states by small changes in the excitation intensity. The latter promises
various applications in the field of all-optical processing at nanoscale, the
most underlying of them being the volatile optical memory.Comment: 6 two column pages, 5 figures, to appear in Phys. Rev.
Self-organized circular flow of classical point particles
We consider newtonian dynamics of charged particles on the circle with
nearest neigbour interaction with Coulomb repulsive potential . Also
there is an external accelerating force which is nonzero only on a small part
of the circle. We construct homogeneous solutions where the velocities of all
particles are approximately equal and their density is approximately uniform.
This gives a qualitative mathematical model for some features of the direct
electric current (DC), in agreement with a suggestion by R. Feynman
Monitoring the localization-delocalization transition within a 1D model with non-random long-range interaction
We consider a two-parameter one-dimensional Hamiltonian with uncorrelated
diagonal disorder and {\it non-random} long-range inter-site interaction
. The model is critical at and reveals the
localization-delocalization transition with respect to the disorder magnitude.
To detect the transition we analyze level and wave function statistics. It is
demonstrated also that in the marginal case () all states are
localized.Comment: 4 pages, 5 figure
Environment effects on the electric conductivity of the DNA
We present a theoretical analysis of the environment effects on charge
transport in double-stranded synthetic poly(G)-poly(C) DNA molecules attached
to two ideal leads. Coupling of the DNA to the environment results in two
effects: (i) localization of carrier functions due to the static disorder and
(ii) phonon-induced scattering of the carrier between these localized states,
resulting in hopping conductivity. A nonlinear Pauli master equation for
populations of localized states is used to describe the hopping transport and
calculate the electric current as a function of the applied bias. We
demonstrate that, although the electronic gap in the density of states shrinks
as the disorder increases, the voltage gap in the characteristics becomes
wider. Simple physical explanation of this effect is provided.Comment: 8 pages, 2 figures, to appear in J. Phys.: Condens. Matte
KMS states on Quantum Grammars
We consider quantum (unitary) continuous time evolution of spins on a lattice
together with quantum evolution of the lattice itself. In physics such
evolution was discussed in connection with quantum gravity. It is also related
to what is called quantum circuits, one of the incarnations of a quantum
computer. We consider simpler models for which one can obtain exact
mathematical results. We prove existence of the dynamics in both Schroedinger
and Heisenberg pictures, construct KMS states on appropriate C*-algebras. We
show (for high temperatures) that for each system where the lattice undergoes
quantum evolution, there is a natural scaling leading to a quantum spin system
on a fixed lattice, defined by a renormalized Hamiltonian.Comment: 22 page
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