112 research outputs found
Electron Coherence in Mesoscopic Kondo Wires
We present measurements of the magnetoresistance of long and narrow quasi
one-dimensional gold wires containing magnetic iron impurities. The electron
phase coherence time extracted from the weak antilocalisation shows a
pronounced plateau in a temperature region of 300 mK - 800 mK, associated with
the phase breaking due to the Kondo effect. Below the Kondo temperature, the
phase coherence time increases, as expected in the framework of Kondo physics.
At much lower temperatures, the phase coherence time saturates again, in
contradiction with standard Fermi liquid theory. In the same temperature
regime, the resistivity curve displays a characteristic maximum at zero
magnetic field, associated with the formation of a spin glass state. We argue
that the interactions between the magnetic moments are responsible for the low
temperature saturation of the phase coherence time.Comment: To appear in Advances in Solid State Physics, Vol 43, edited by B.
Kramer (Springer Verlag, Berlin 2003
Sources and sinks separating domains of left- and right-traveling waves: Experiment versus amplitude equations
In many pattern forming systems that exhibit traveling waves, sources and
sinks occur which separate patches of oppositely traveling waves. We show that
simple qualitative features of their dynamics can be compared to predictions
from coupled amplitude equations. In heated wire convection experiments, we
find a discrepancy between the observed multiplicity of sources and theoretical
predictions. The expression for the observed motion of sinks is incompatible
with any amplitude equation description.Comment: 4 pages, RevTeX, 3 figur
Multiple Current States of Two Phase-Coupled Superconducting Rings
The states of two phase-coupled superconducting rings have been investigated.
Multiple current states have been revealed in the dependence of the critical
current on the magnetic field. The performed calculations of the critical
currents and energy states in a magnetic field have made it possible to
interpret the experiment as the measurement of energy states into which the
system comes with different probabilities because of the equilibrium and
non-equilibrium noises upon the transition from the resistive state to the
superconducting state during the measurement of the critical currentComment: 5 pages, 5 figure
Spin Fluctuation Induced Dephasing in a Mesoscopic Ring
We investigate the persistent current in a hybrid Aharonov-Bohm ring -
quantum dot system coupled to a reservoir which provides spin fluctuations. It
is shown that the spin exchange interaction between the quantum dot and the
reservoir induces dephasing in the absence of direct charge transfer. We
demonstrate an anomalous nature of this spin-fluctuation induced dephasing
which tends to enhance the persistent current. We explain our result in terms
of the separation of the spin from the charge degree of freedom. The nature of
the spin fluctuation induced dephasing is analyzed in detail.Comment: 4 pages, 4 figure
Regular dendritic patterns induced by non-local time-periodic forcing
The dynamic response of dendritic solidification to spatially homogeneous
time-periodic forcing has been studied. Phase-field calculations performed in
two dimensions (2D) and experiments on thin (quasi 2D) liquid crystal layers
show that the frequency of dendritic side-branching can be tuned by oscillatory
pressure or heating. The sensitivity of this phenomenon to the relevant
parameters, the frequency and amplitude of the modulation, the initial
undercooling and the anisotropies of the interfacial free energy and molecule
attachment kinetics, has been explored. It has been demonstrated that besides
the side-branching mode synchronous with external forcing as emerging from the
linear Wentzel-Kramers-Brillouin analysis, modes that oscillate with higher
harmonic frequencies are also present with perceptible amplitudes.Comment: 15 pages, 23 figures, Submitted to Phys. Rev.
Persistent currents in mesoscopic rings: A numerical and renormalization group study
The persistent current in a lattice model of a one-dimensional interacting
electron system is systematically studied using a complex version of the
density matrix renormalization group algorithm and the functional
renormalization group method. We mainly focus on the situation where a single
impurity is included in the ring penetrated by a magnetic flux. Due to the
interplay of the electron-electron interaction and the impurity the persistent
current in a system of N lattice sites vanishes faster then 1/N. Only for very
large systems and large impurities our results are consistent with the
bosonization prediction obtained for an effective field theory. The results
from the density matrix renormalization group and the functional
renormalization group agree well for interactions as large as the band width,
even though as an approximation in the latter method the flow of the
two-particle vertex is neglected. This confirms that the functional
renormalization group method is a very powerful tool to investigate correlated
electron systems. The method will become very useful for the theoretical
description of the electronic properties of small conducting ring molecules.Comment: 9 pages, 8 figures include
Wave patterns generated by an axisymmetric obstacle in a two-layer flow
Gravity waves generated by a moving obstacle in a two-layer stratified fluid are investigated. The experimental configuration is three-dimensional with an axisymmetric obstacle which is towed in one of the two layers. The experimental method used in the present study is based on a stereoscopic technique allowing the 3D reconstruction of the interface between the two layers. Investigation into the wave pattern as a function of the Froude number, Fr, based on the relative density of the fluid layers and the velocity of the towed obstacle is presented. Specific attention is paid to the transcritical regime for which Fr is close to one. Potential energy trapped in the wave field patterns is also extracted from the experimental results and is analyzed as a function of both the Froude number, Fr, and the transcritical similarity parameter Γ. In particular, a remarkable increase in the potential energy around Fr = 1 is observed and a scaling allowing to assemble data resulting from different experimental parameters is proposed
Individual Preferences and Social Interactions Determine the Aggregation of Woodlice
n°e17389.info:eu-repo/semantics/publishe
Observation of Persistent Currents in Mesoscopic Connected Rings
Revised version of the paper cond-mat/0007396. Also available on request in any formatWe report measurements of the low temperature magnetic response of a line of 16 GaAs/GaAlAs \emph{connected} mesoscopic rings whose total length is much larger than . Using an on-chip micro-\textsc{squid} technology, we have measured a periodic response, with period , corresponding to persistent currents in the rings of typical amplitude per ring. Direct comparison with measurements on the same rings but \emph{isolated} is presented
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