1,581 research outputs found
Coulomb blockade at a tunnel junction between two quantum wires with long-range interaction
The non-linear current-voltage characteristic of a tunnel junction between
two Luttinger systems is calculated for an interaction with finite range.
Coulomb blockade features are found. The dissipative resistance, the
capacitance and the external impedance, which were introduced ad hoc in earlier
theories, are obtained in terms of the electron-electron interaction. The
frequency dependence of the impedance is given by the excitation spectrum of
the electrons.Comment: 5 pages, RevTeX, 2 figures, to be published in Solid State
Communication
Electron correlations and single-particle physics in the Integer Quantum Hall Effect
The compressibility of a two-dimensional electron system with spin in a
spatially correlated random potential and a quantizing magnetic field is
investigated. Electron-electron interaction is treated with the Hartree-Fock
method. Numerical results for the influences of interaction and disorder on the
compressibility as a function of the particle density and the strength of the
magnetic field are presented. Localization-delocalization transitions
associated with highly compressible region in the energy spectrum are found at
half-integer filling factors. Coulomb blockade effects are found near integer
fillings in the regions of low compressibility. Results are compared with
recent experiments.Comment: 4 pages, 2 figures, replaced with revised versio
Data Quality in Predictive Toxicology: Identification of Chemical Structures and Calculation of Chemical Descriptors
Every technique for toxicity prediction and for the detection of structure–activity relationships relies on the accurate estimation and representation of chemical and toxicologic properties. In this paper we discuss the potential sources of errors associated with the identification of compounds, the representation of their structures, and the calculation of chemical descriptors. It is based on a case study where machine learning techniques were applied to data from noncongeneric compounds and a complex toxicologic end point (carcinogenicity). We propose methods applicable to the routine quality control of large chemical datasets, but our main intention is to raise awareness about this topic and to open a discussion about quality assurance in predictive toxicology. The accuracy and reproducibility of toxicity data will be reported in another paper
On ground states of interacting Composite Fermions with spin at half filling
The effects of interactions in a 2D electron system in a strong magnetic
field of two degenerate Landau levels with opposite spins and at filling
factors 1/2 are studied. Using the Chern-Simons gauge transformation, the
system is mapped to Composite Fermions. The fluctuations of the gauge field
induce an effective interaction between the Composite Fermions which can be
attractive in both the particle-particle and in the particle-hole channel. As a
consequence, a spin-singlet (s-wave) ground state of Composite Fermions can
exist with a finite pair-breaking energy gap for particle-particle or
particle-hole pairs. The competition between these two possible ground states
is discussed. For long-range Coulomb interaction the particle-particle state is
favored if the interaction strength is small. With increasing interaction
strength there is a crossover towards the particle-hole state. If the
interaction is short range, only the particle-particle state is possible.Comment: REVTEX; 12 pages, 5 figures; submitted to Phisical Review
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
Local fields in nonlinear quantum transport
We investigate the dynamical interplay between currents and electromagnetic
fields in frequency-dependent transport through a single-channel quantum wire
with an impurity potential in the presence of electron-electron interactions.
We introduce and discuss a formalism which allows a self-consistent treatment
of currents and electromagnetic fields.Comment: 4 page
Calculation of Mutual Information for Partially Coherent Gaussian Channels with Applications to Fiber Optics
The mutual information between a complex-valued channel input and its
complex-valued output is decomposed into four parts based on polar coordinates:
an amplitude term, a phase term, and two mixed terms. Numerical results for the
additive white Gaussian noise (AWGN) channel with various inputs show that, at
high signal-to-noise ratio (SNR), the amplitude and phase terms dominate the
mixed terms. For the AWGN channel with a Gaussian input, analytical expressions
are derived for high SNR. The decomposition method is applied to partially
coherent channels and a property of such channels called "spectral loss" is
developed. Spectral loss occurs in nonlinear fiber-optic channels and it may be
one effect that needs to be taken into account to explain the behavior of the
capacity of nonlinear fiber-optic channels presented in recent studies.Comment: 30 pages, 9 figures, accepted for publication in IEEE Transactions on
Information Theor
Spin polarization in a T-shape conductor induced by strong Rashba spin-orbit coupling
We investigate numerically the spin polarization of the current in the
presence of Rashba spin-orbit interaction in a T-shaped conductor proposed by
A.A. Kiselev and K.W. Kim (Appl. Phys. Lett. {\bf 78} 775 (2001)). The
recursive Green function method is used to calculate the three terminal spin
dependent transmission probabilities. We focus on single-channel transport and
show that the spin polarization becomes nearly 100 % with a conductance close
to for sufficiently strong spin-orbit coupling. This is interpreted
by the fact that electrons with opposite spin states are deflected into an
opposite terminal by the spin dependent Lorentz force. The influence of the
disorder on the predicted effect is also discussed. Cases for multi-channel
transport are studied in connection with experiments
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