5,388 research outputs found
Evanescent incompressible strips as origin of the observed Hall resistance overshoot
In this work we provide a systematic explanation to the unusual non-monotonic
behavior of the Hall resistance observed at two-dimensional electron systems.
We use a semi-analytical model based on the interaction theory of the integer
quantized Hall effect to investigate the existence of the anomalous, \emph{i.e}
overshoot, Hall resistance . The observation of the overshoot resistance
at low magnetic field edge of the plateaus is elucidated by means of
overlapping evanescent incompressible strips, formed due to strong magnetic
fields and interactions. Utilizing a self-consistent numerical scheme we also
show that, if the magnetic field is decreased the decreases to its
expected value. The effects of the sample width, temperature, disorder strength
and magnetic field on the overshoot peaks are investigated in detail. Based on
our findings, we predict a controllable procedure to manipulate the maxima of
the peaks, which can be tested experimentally. Our model does not depend on
specific and intrinsic properties of the material, provided that a single
particle gap exists.Comment: A theoretical follow-up paper of arXiv:1007.258
Interaction Between Motor Domains Can Explain the Complex Dynamics of Heterodimeric Kinesins
Motor proteins are active enzyme molecules that play a crucial role in many
biological processes. They transform the chemical energy into the mechanical
work and move unidirectionally along rigid cytoskeleton filaments.
Single-molecule experiments suggest that motor proteins, consisting of two
motor domains, move in a hand-over-hand mechanism when each subunit changes
between trailing and leading positions in alternating steps, and these subunits
do not interact with each other. However, recent experiments on heterodimeric
kinesins suggest that the motion of motor domains is not independent, but
rather strongly coupled and coordinated, although the mechanism of these
interactions are not known. We propose a simple discrete stochastic model to
describe the dynamics of homodimeric and heterodimeric two-headed motor
proteins. It is argued that interactions between motor domains modify free
energy landscapes of each motor subunit, and motor proteins still move via the
hand-over-hand mechanism but with different transitions rates. Our calculations
of biophysical properties agree with experimental observations. Several ways to
test the theoretical model are proposed.Comment: To appear in New J. Phy
Electronic transport characterization of AlGaN/GaN heterostructures using quantitative mobility spectrum analysis
Cataloged from PDF version of article.Resistivity and Hall effect measurements in nominally undoped Al0.25Ga0.75N/GaN heterostructures grown on sapphire substrate by metal-organic chemical vapor deposition are carried out as a function of temperature (20-350 K) and magnetic field (0-1.5 T). The measurement results are analyzed using the quantitative mobility spectrum analysis techniques. It is found that there is strong two-dimensional electron gas localization below 100 K, while the thermally activated minority carriers with the activation energies of similar to 58 and similar to 218 meV contribute to the electron transport at high temperatures. (C) 2007 American Institute of Physics
- …