52 research outputs found
Spin-dependent shot noise enhancement in a quantum dot
The spin-dependent dynamical blockade was investigated in a lateral quantum
dot in a magnetic field. Spin-polarized edge channels in the two-dimensional
leads and the spatial distribution of Landau orbitals in the dot modulate the
tunnel coupling of the quantum dot level spectrum. In a measurement of the
electron shot noise we observe a pattern of super-Poissonian noise which is
correlated to the spin-dependent competition between different transport
channels
High-order cumulants in the counting statistics of asymmetric quantum dots
Measurements of single electron tunneling through a quantum dot using a
quantum point contact as charge detector have been performed for very long time
traces with very large event counts. This large statistical basis is used for a
detailed examination of the counting statistics for varying symmetry of the
quantum dot system. From the measured statistics we extract high order
cumulants describing the distribution. Oscillations of the high order cumulants
are observed when varying the symmetry. We compare this behavior to the
observed oscillation in time dependence and show that the variation of both
system variables lead to the same kind of oscillating response.Comment: 3 page
Der Plateau-Übergang im Quanten-Hall-Effekt : Experimente zur Temperatur- und Frequenzabhängigkeit
[no abstract
Dopant-controlled single-electron pumping through a metallic island
We investigate a hybrid metallic island / single dopant electron pump based
on fully-depleted silicon on insulator technology. Electron transfer between
the central metallic island and the leads is controlled by resonant tunneling
through single phosphorus dopants in the barriers. Top gates above the barriers
are used control the resonance conditions. Applying radio frequency signals to
the gates, non-adiabatic quantized electron pumping is achieved. A simple
deterministic model is presented and confirmed by comparing measurements with
simulations
High cumulants in the counting statistics measured for a quantum dot
We report on measurements of single electron tunneling through a quantum dot
using a quantum point contact as non-invasive charge detector with fast time
response. We elaborate on the unambiguous identification of individual
tunneling events and determine the distribution of transferred charges, the
so-called full counting statistics. We discuss our data analysis, including the
error estimates of the measurement, and show that the quality of our
experimental results is sufficiently high to extract cumulants of the
distribution up to the 20th order for short times.Comment: 4 pages, 3 figures, Contribution to EP2DS18-MSS14, Kobe, Japan, July
200
A quantized current source with mesoscopic feedback
We study a mesoscopic circuit of two quantized current sources, realized by
non-adiabatic single- electron pumps connected in series with a small
micron-sized island in between. We find that quantum transport through the
second pump can be locked onto the quantized current of the first one by a
feedback due to charging of the mesoscopic island. This is confirmed by a
measurement of the charge variation on the island using a nearby charge
detector. Finally, the charge feedback signal clearly evidences loading into
excited states of the dynamic quantum dot during single-electron pump
operation
Integrated quantized electronics: a semiconductor quantized voltage source
The Josephson effect in superconductors links a quantized output voltage Vout
= f \cdot(h/2e) to the natural constants of the electron's charge e, Planck's
constant h, and to an excitation frequency f with important applications in
electrical quantum metrology. Also semiconductors are routinely applied in
electrical quantum metrology making use of the quantum Hall effect. However,
despite their broad range of further applications e.g. in integrated circuits,
quantized voltage generation by a semiconductor device has never been obtained.
Here we report a semiconductor quantized voltage source generating quantized
voltages Vout = f\cdot(h/e). It is based on an integrated quantized circuit of
a single electron pump operated at pumping frequency f and a quantum Hall
device monolithically integrated in series. The output voltages of several \muV
are expected to be scalable by orders of magnitude using present technology.
The device might open a new route towards the closure of the quantum
metrological triangle. Furthermore it represents a universal electrical quantum
reference allowing to generate quantized values of the three most relevant
electrical units of voltage, current, and resistance based on fundamental
constants using a single device.Comment: 15 pages, 3 figure
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