55 research outputs found
Quantum Interference and Inelastic Scattering in a Model Which-Way Device
A which-way device is one which is designed to detect which of 2 paths is
taken by a quantum particle, whether Schr\"odinger's cat is dead or alive. One
possible such device is represented by an Aharonov-Bohm ring with a quantum dot
on one branch. A charged cantilever or spring is brought close to the dot as a
detector of the presence of an electron. The conventional view of such a device
is that any change in the state of the cantilever implies a change in the
electron state which will in turn destroy the interference effects. In this
paper we show that it is in fact possible to change the state of the oscillator
while preserving the quantum interference phenomenon.Comment: 5 pages, 7 figures, Localisation 2002 Toky
Calculation of the current response in a nanojunction for an arbitrary time-dependent bias: application to the molecular wire
Recently [Phys. Rev. B 91, 125433 (2015)] we derived a general formula for
the time-dependent quantum electron current through a molecular junction
subject to an arbitrary time-dependent bias within the Wide Band Limit
Approximation (WBLA) and assuming a single particle Hamiltonian. Here we
present an efficient numerical scheme for calculating the current and particle
number. Using the Pad\'e expansion of the Fermi function, it is shown that all
frequency integrals occurring in the general formula for the current can be
removed analytically. Furthermore, when the bias in the reservoirs is assumed
to be sinusoidal it is possible to manipulate the general formula into a form
containing only summations over special functions. To illustrate the method, we
consider electron transport through a one-dimensional molecular wire coupled to
two leads subject to out-of-phase biases. We also investigate finite size
effects in the current response and particle number that results from the
switch-on of such a bias
Diffraction and database analyses of photoactive biphenyl compounds and novel carbaborane structures
The research involved in this thesis is mainly concerned with crystallography and the analysis using crystallographic techniques and methods. The work in this thesis is centered mainly on two types of chemical compounds, photoactive compounds and carbaboranes. The first is the photoactive compounds of biphenyl, its derivatives and similar compounds; these compounds have been studied by diffraction and database analysis. The photochemistry and subsequent structural analysis of biphenyls has been studied in collaboration with Professor Peter Wan at the University of Victoria, Canada. In this study Professor Wan and his group conducted all synthesis and spectroscopic analysis, including the photochemical analysis. In a similar study although not with biphenyls, the a-azidocinnamates were investigated in collaboration with Professor Meth-Cohn of the University of Sunderland. Professor Meth-Cohn and his group conducted all synthesis and spectroscopic analysis. The biphenyl type compounds have also been studied using database analysis to examine the bond lengths, torsion angles, inter-/intra-molecular interactions and general packing conformations and interactions within these structures and this analysis was used to study several conformational anomalies that exist in biphenyl derivative compounds. The second chemical type is carbaboranes; these compounds have been examined in collaboration with Professor Wade's group at the University of Durham. The analysis of carbaboranes centers mainly on hydrogen bonding however also expands into several novel carbaborane structures. Professor Wade and his group carried out the synthesis and spectroscopic analysis
Finite Size Scaling Analysis of the Anderson Transition
This chapter describes the progress made during the past three decades in the
finite size scaling analysis of the critical phenomena of the Anderson
transition. The scaling theory of localisation and the Anderson model of
localisation are briefly sketched. The finite size scaling method is described.
Recent results for the critical exponents of the different symmetry classes are
summarised. The importance of corrections to scaling are emphasised. A
comparison with experiment is made, and a direction for future work is
suggested.Comment: 12 pages, 1 figure. "Fifty Years of Anderson localization", edited by
E. Abrahams (World Scientific, Singapore, 2010
Disorder and interactions in one-dimensional systems
Published versio
Quantum gears: a simple mechanical system in the quantum regime
Abstract. The quantum mechanics of a simple mechanical system is considered. A group of gears can serve as a model for several different systems such as an artifically constructed nanomechanical device or a group of ring molecules. It is shown that the classical motion of the gears in which the angular velocities are locked together does not correspond to
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