32 research outputs found
Edge Channel Interference Controlled by Landau Level Filling
We study the visibility of Aharonov-Bohm interference in an electronic
Mach-Zehnder interferometer (MZI) in the integer quantum Hall regime. The
visibility is controlled by the filling factor and is observed only
between and 1.0, with an unexpected maximum near .
Three energy scales extracted from the temperature and voltage dependences of
the visibility change in a very similar way with the filling factor, indicating
that the different aspects of the interference depend sensitively on the local
structure of the compressible and incompressible strips forming the quantum
Hall edge channels.Comment: 5 pages, 5 figures, final version accepted for publication in Phys.
Rev.
Counting Statistics and Dephasing Transition in an Electronic Mach-Zehnder Interferometer
It was recently suggested that a novel type of phase transition may occur in
the visibility of electronic Mach-Zehnder Interferometers. Here, we present
experimental evidence for the existence of this transition. The transition is
induced by strongly non-Gaussian noise that originates from the strong coupling
of a quantum point contact to the interferometer. We provide a transparent
physical picture of the effect, by exploiting a close analogy to the
neutrino-oscillations of particle physics. In addition, our experiment
constitutes a probe of the singularity of the elusive full counting statistics
of a quantum point contact.Comment: 7 pages, 4 figures (+Supplement 8 pages, 9 figures
Nonlocal vortex motion in mesoscopic amorphous Nb0.7Ge0.3 structures
We study nonlocal vortex transport in mesoscopic amorphous Nb0.7Ge0.3
samples. A dc current I is passed through a wire connected via a perpendicular
channel, of a length L= 2-5 um, with a pair of voltage probes where a nonlocal
response Vnl ~ I is measured. The maximum of Rnl=Vnl/I for a given temperature
occurs at an L-independent magnetic field and is proportional to 1/L. The
results are interpreted in terms of the dissipative vortex motion along the
channel driven by a remote current, and can be understood in terms of a simple
model.Comment: 4 pages, 3 figure
A conservative coupling algorithm between a compressible flow and a rigid body using an Embedded Boundary method
This paper deals with a new solid-fluid coupling algorithm between a rigid
body and an unsteady compressible fluid flow, using an Embedded Boundary
method. The coupling with a rigid body is a first step towards the coupling
with a Discrete Element method. The flow is computed using a Finite Volume
approach on a Cartesian grid. The expression of numerical fluxes does not
affect the general coupling algorithm and we use a one-step high-order scheme
proposed by Daru and Tenaud [Daru V,Tenaud C., J. Comput. Phys. 2004]. The
Embedded Boundary method is used to integrate the presence of a solid boundary
in the fluid. The coupling algorithm is totally explicit and ensures exact mass
conservation and a balance of momentum and energy between the fluid and the
solid. It is shown that the scheme preserves uniform movement of both fluid and
solid and introduces no numerical boundary roughness. The effciency of the
method is demonstrated on challenging one- and two-dimensional benchmarks
A rarefaction-tracking method for hyperbolic conservation laws
We present a numerical method for scalar conservation laws in one space
dimension. The solution is approximated by local similarity solutions. While
many commonly used approaches are based on shocks, the presented method uses
rarefaction and compression waves. The solution is represented by particles
that carry function values and move according to the method of characteristics.
Between two neighboring particles, an interpolation is defined by an analytical
similarity solution of the conservation law. An interaction of particles
represents a collision of characteristics. The resulting shock is resolved by
merging particles so that the total area under the function is conserved. The
method is variation diminishing, nevertheless, it has no numerical dissipation
away from shocks. Although shocks are not explicitly tracked, they can be
located accurately. We present numerical examples, and outline specific
applications and extensions of the approach.Comment: 21 pages, 7 figures. Similarity 2008 conference proceeding
Entropy Stable Finite Volume Approximations for Ideal Magnetohydrodynamics
This article serves as a summary outlining the mathematical entropy analysis of the ideal magnetohydrodynamic (MHD) equations. We select the ideal MHD equations as they are particularly useful for mathematically modeling a wide variety of magnetized fluids. In order to be self-contained we first motivate the physical properties of a magnetic fluid and how it should behave under the laws of thermodynamics. Next, we introduce a mathematical model built from hyperbolic partial differential equations (PDEs) that translate physical laws into mathematical equations. After an overview of the continuous analysis, we thoroughly describe the derivation of a numerical approximation of the ideal MHD system that remains consistent to the continuous thermodynamic principles. The derivation of the method and the theorems contained within serve as the bulk of the review article. We demonstrate that the derived numerical approximation retains the correct entropic properties of the continuous model and show its applicability to a variety of standard numerical test cases for MHD schemes. We close with our conclusions and a brief discussion on future work in the area of entropy consistent numerical methods and the modeling of plasmas
Effect of vortex-core size on the flux lattice in a mesoscopic superconducting strip
We present an experimental study of the vortex-motion dissipation in a mesoscopic amorphous (a-)Nb0.7Ge0.3 strip, with emphasis on the results for 3-8 vortex rows parallel to the long strip axis. In the isothermal voltage vs magnetic field traces, at a constant current, we observe plateaus superimposed onto a monotonic background. The plateaus appear because finite vortex-core size influences the accommodation of the flux lattice into the strip. This conclusion is drawn from a quantitative analysis, which is free of adjustable parameters, of the magnetic fields that edge the plateaus