325 research outputs found
Quantum Spin Holography with Surface State Electrons
In a recent paper Moon and coworkers [C.R. Moon et al., Nature Nanotechnology
4, 167 (2009)] have shown that the single-atom limit for information storage
density can be overcome by using the coherence of electrons in a
two-dimensional electron gas to produce quantum holograms comprised of
individually manipulated molecules projecting an electronic pattern onto a
portion of a surface. We propose to further extend the concept by introducing
quantum spin holography - a version of quantum holographic encoding allowing to
store the information in two spin channels independently.Comment: 5 pages, 3 figure
Особливості адміністративно-територіальної реформи Польщі
Розглянуто адміністративно – територіальний устрій Польщі до проведення реформи
1998р. Проаналізовано адміністративно-територіальні перетворення, що відбулися в Польщі в результаті проведення реформи 1998р. Автор розглядає можливість використання
польського досвіду, щодо зміни адміністративно – територіального устрою в Україні.
The article deals with the administrative - territorial division of Poland to the reform of 1998.
Analyzed administrative - territorial changes that took place in Poland as a result of the reform of
1998. The author examines the possibility of using the Polish experience to change the
administrative - territorial structure of Ukraine
Confined bulk states as a long-range sensor for impurities and a transfer channel for quantum information
We show that confinement of bulk electrons can be observed at low-dimensional
surface structures and can serve as a long-range sensor for the magnetism and
electronic properties of single impurities or as a quantum information transfer
channel with large coherence lengths. Our ab initio calculations reveal
oscillations of electron density in magnetic chains on metallic surfaces and
help to unambiguously identify the electrons involved as bulk electrons. We
furthermore discuss the possibility of utilizing bulk state confinement to
transfer quantum information, encoded in an atom's species or spin, across
distances of several nanometers with high efficiency.Comment: 5 pages, 2 figure
Tailoring exchange interactions in engineered nanostructures: Ab initio study
We present a novel approach to spin manipulation in atomic-scale
nanostructures. Our ab initio calculations clearly demonstrate that it is
possible to tune magnetic properties of sub-nanometer structures by adjusting
the geometry of the system. By the example of two surface-based systems we
demonstrate that (i) the magnetic moment of a single adatom coupled to a buried
magnetic Co layer can be stabilized in either a ferromagnetic or an
antiferromagnetic configuration depending on the spacer thickness. It is found
that a buried Co layer has a profound effect on the exchange interaction
between two magnetic impurities on the surface. (ii) The exchange interaction
between magnetic adatoms can be manipulated by introducing artificial
nonmagnetic Cu chains to link them.Comment: 4 pages, submitted to PR
Relativistic peculiarities at stepped surfaces: surprising energetics and unexpected diffusion patterns
We revive intriguing, yet still unexplained, experimental results of Ehrlich
and co-workers [ Phys. Rev. Lett. 77 1334 (1996); Phys. Rev. Lett. 67 2509
(1991)] who have observed, that 5d adatoms distributed on (111) surface islands
of 5d metals favor the adsorption at the cluster's edge rather than at the
cluster's interior, which lies in contrast with the behavior of 4d and 3d
elements. Our state of the art ab initio calculations demonstrate that such
behavior is a direct consequence of the relativity of 5d metals.Comment: 5 pages, 5 figure
Tailoring exchange interactions in engineered nanostructures: Ab initio study
We present a novel approach to spin manipulation in atomic-scale
nanostructures. Our ab initio calculations clearly demonstrate that it is
possible to tune magnetic properties of sub-nanometer structures by adjusting
the geometry of the system. By the example of two surface-based systems we
demonstrate that (i) the magnetic moment of a single adatom coupled to a buried
magnetic Co layer can be stabilized in either a ferromagnetic or an
antiferromagnetic configuration depending on the spacer thickness. It is found
that a buried Co layer has a profound effect on the exchange interaction
between two magnetic impurities on the surface. (ii) The exchange interaction
between magnetic adatoms can be manipulated by introducing artificial
nonmagnetic Cu chains to link them.Comment: 4 pages, submitted to PR
Catalytic molecularly imprinted polymer membranes: Development of the biomimetic sensor for phenols detection
Portable biomimetic sensor devices for the express control of phenols content in
water were developed. The synthetic binding sites mimicking active site of the
enzyme tyrosinase were formed in the structure of free-standing molecularly
imprinted polymer membranes. Molecularly imprinted polymer membranes with the
catalytic activity were obtained by co-polymerization of the complex Cu
(II)–catechol–urocanic acid ethyl ester with (tri)ethyleneglycoldimethacrylate,
and oligourethaneacrylate. Addition of the elastic component
oligourethaneacrylate provided formation of the highly cross-linked polymer with
the catalytic activity in a form of thin, flexible, and mechanically stable
membrane. High accessibility of the artificial catalytic sites for the
interaction with the analyzed phenol molecules was achieved due to addition of
linear polymer (polyethyleneglycol Mw 20,000) to the initial monomer mixture
before the polymerization. As a result, typical semi-interpenetrating polymer
networks (semi-IPNs) were formed. The cross-linked component of the semi-IPN was
represented by the highly cross-linked catalytic molecularly imprinted polymer,
while the linear one was represented by polyethyleneglycol Mw 20,000. Extraction
of the linear polymer from the fully formed semi-IPN resulted in formation of
large pores in the membranes’ structure. Concentration of phenols in the
analyzed samples was detected using universal portable device oxymeter with the
oxygen electrode in a close contact with the catalytic molecularly imprinted
polymer membrane as a transducer. The detection limit of phenols detection using
the developed sensor system based on polymers–biomimics with the optimized
composition comprised 0.063 mM, while the linear range of the sensor comprised
0.063–1 mM. The working characteristics of the portable sensor devices were
investigated. Storage stability of sensor systems at room temperature comprised
12 months (87%). As compared to traditional methods of phenols detection the
developed sensor system is characterized by simplicity of operation,
compactness, an
Potential Energy Driven Spin Manipulation via a Controllable Hydrogen Ligand
Spin-bearing molecules can be stabilized on surfaces and in junctions with
desirable properties such as a net spin that can be adjusted by external
stimuli. Using scanning probes, initial and final spin states can be deduced
from topographic or spectroscopic data, but how the system transitioned between
these states is largely unknown. Here we address this question by manipulating
the total spin of magnetic cobalt hydride complexes on a corrugated boron
nitride surface with a hydrogen- functionalized scanning probe tip by
simultaneously tracking force and conductance. When the additional hydrogen
ligand is brought close to the cobalt monohydride, switching between a corre-
lated S = 1 /2 Kondo state, where host electrons screen the magnetic moment,
and a S = 1 state with magnetocrystalline anisotropy is observed. We show that
the total spin changes when the system is transferred onto a new potential
energy surface defined by the position of the hydrogen in the junction. These
results show how and why chemically functionalized tips are an effective tool
to manipulate adatoms and molecules, and a promising new method to selectively
tune spin systems
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