1,020 research outputs found
Cryogenic scanning force microscopy of quantum Hall samples: Adiabatic transport originating in anisotropic depletion at contact interfaces
Anisotropic magneto resistances and intrinsic adiabatic transport features
are generated on quantum Hall samples based on an (Al,Ga)As/GaAs
heterostructure with alloyed Au/Ge/Ni contacts. We succeed to probe the
microscopic origin of these transport features with a cryogenic scanning force
microscope (SFM) by measuring the local potential distribution within the
two-dimensional electron system (2DES). These local measurements reveal the
presence of an incompressible strip in front of contacts with insulating
properties depending on the orientation of the contact/2DES interface line
relatively to the crystal axes of the heterostructure. Such an observation
gives another microscopic meaning to the term 'non-ideal contact' used in
context with the Landauer-B\"uttiker formalism applied to the quantum Hall
effect.Comment: 5 pages, 4 figure
Density of States of GaAs-AlGaAs Heterostructures Deduced from Temperature Dependend Magnetocapacitance Measurements
Abstract We have analyzed the density of states of a two dimensional electron gas in a GaAs- AlGaAs hetereostructure by measuring the magnetocapacitance in magnetic fields up to 6 Tesla at temperatures below 10 K. The experimental data are well described by a Gaussian-like density of states where the linewidth à is proportional to B
Density of States in Landau Level Tails of GaAs-AlxGa1-xAs Heterostructures
From an analysis of the thermally activated resistivity as a function of the magnetic field in the quantum Hall regime we deduced the position of the Fermi energy in the mobility gap as a function of the filling factor and therefore the density of states. The measured density of states is best described by a Gaussian like profile superimposed on a constant background
Chalker-Coddington model described by an S-matrix with odd dimensions
The Chalker-Coddington network model is often used to describe the transport
properties of quantum Hall systems. By adding an extra channel to this model,
we introduce an asymmetric model with profoundly different transport
properties. We present a numerical analysis of these transport properties and
consider the relevance for realistic systems.Comment: 7 pages, 4 figures. To appear in the EP2DS-17 proceeding
Correlated electron tunneling through two separate quantum dot systems with strong capacitive interdot coupling
A system consisting of two independently contacted quantum dots with strong
electrostatic interaction shows interdot Coulomb blockade when the dots are
weakly tunnel coupled to their leads. It is studied experimentally how the
blockade can be overcome by correlated tunneling when tunnel coupling to the
leads increases. The experimental results are compared with numerical
renormalization group calculations using predefined (measured) parameters. Our
results indicate Kondo correlations due to the electrostatic interaction in
this double quantum dot system.Comment: 5 pages, 3 figures, published in Phys. Rev. Lett. Oct. 30t
Interlayer tunneling in counterflow experiments on the excitonic condensate in quantum Hall bilayers
The effect of tunneling on the transport properties of} quantum Hall double
layers in the regime of the excitonic condensate at total filling factor one is
studied in counterflow experiments. If the tunnel current is smaller than a
critical , tunneling is large and is effectively shorting the two layers.
For tunneling becomes negligible. Surprisingly, the transition
between the two tunneling regimes has only a minor impact on the features of
the filling-factor one state as observed in magneto-transport, but at currents
exceeding the resistance along the layers increases rapidly
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