27 research outputs found
High-resolution error detection in the capture process of a single-electron pump
The dynamic capture of electrons in a semiconductor quantum dot (QD) by raising a potential
barrier is a crucial stage in metrological quantized charge pumping. In this work, we use a quantum
point contact (QPC) charge sensor to study errors in the electron capture process of a QD formed in
a GaAs heterostructure. Using a two-step measurement protocol to compensate for 1/f noise in the
QPC current, and repeating the protocol more than 106 times, we are able to resolve errors with
probabilities of order 106. For the studied sample, one-electron capture is affected by errors in
30 out of every million cycles, while two-electron capture was performed more than 106 times
with only one error. For errors in one-electron capture, we detect both failure to capture an electron
and capture of two electrons. Electron counting measurements are a valuable tool for investigating
non-equilibrium charge capture dynamics, and necessary for validating the metrological accuracy
of semiconductor electron pumps
Quantized charge transport through a static quantum dot using a surface acoustic wave
We present a detailed study of the surface acoustic wave mediated quantized
transport of electrons through a split gate device containing an impurity
potential defined quantum dot within the split gate channel. A new regime of
quantized transport is observed at low RF powers where the surface acoustic
wave amplitude is comparable to the quantum dot charging energy. In this regime
resonant transport through the single-electron dot state occurs which we
interpret as turnstile-like operation in which the traveling wave amplitude
modulates the entrance and exit barriers of the quantum dot in a cyclic fashion
at GHz frequencies. For high RF powers, where the amplitude of the surface
acoustic wave is much larger than the quantum dot energies, the quantized
acoustoelectric current transport shows behavior consistent with previously
reported results. However, in this regime, the number of quantized current
plateaus observed and the plateau widths are determined by the properties of
the quantum dot, demonstrating that the microscopic detail of the potential
landscape in the split gate channel has a profound influence on the quantized
acoustoelectric current transport.Comment: 9 page
Realization of a Quantum Standard for AC Voltage: Overview of a European Research Project
Low-Temperature Specific Heat of an Extreme-Type-II Superconductor at High Magnetic Fields
We present a detailed study of the quasiparticle contribution to the
low-temperature specific heat of an extreme type-II superconductor at high
magnetic fields. Within a T-matrix approximation for the self-energies in the
mixed state of a homogeneous superconductor, the electronic specific heat is a
linear function of temperature with a linear- coefficient
being a nonlinear function of magnetic field . In the range of magnetic
fields H\agt (0.15-0.2)H_{c2} where our theory is applicable, the calculated
closely resembles the experimental data for the borocarbide
superconductor YNiBC.Comment: 7 pages, 2 figures, to appear in Physical Review
Coherent quantum transport in narrow constrictions in the presence of a finite-range longitudinally polarized time-dependent field
We have studied the quantum transport in a narrow constriction acted upon by
a finite-range longitudinally polarized time-dependent electric field. The
electric field induces coherent inelastic scatterings which involve both
intra-subband and inter-sideband transitions. Subsequently, the dc conductance
G is found to exhibit suppressed features. These features are recognized as the
quasi-bound-state (QBS) features which are associated with electrons making
transitions to the vicinity of a subband bottom, of which the density of states
is singular. Having valley-like instead of dip-like structures, these QBS
features are different from the G characteristics for constrictions acted upon
by a finite-range time-modulated potential. In addition, the subband bottoms in
the time-dependent electric field region are shifted upward by an energy
proportional to the square of the electric field and inversely proportional to
the square of the frequency. This effective potential barrier is originated
from the square of the vector potential and it leads to the interesting
field-sensitive QBS features. An experimental set-up is proposed for the
observation of these features.Comment: 8 pages, 4 figure
Far-infrared magneto-optics of low dimensional semiconductor structures and organic conductors
Contains fulltext :
mmubn000001_17285735x.pdf (publisher's version ) (Open Access)Promotores : H. van Kempen en J. Perenboom139 p
Magnetic-field-dependent energy levels in a highly anisotropic electronic material
Contains fulltext :
112818.pdf (publisher's version ) (Open Access
FIR-spectroscopy of the FI-SDW excitation spectrum in a quasi-1D organic conductor
Contains fulltext :
29389.pdf (publisher's version ) (Open Access
Far-infrared cyclotron resonance study of electron dynamics in (BEDT-TTF)2KHg(SCN)4
Contains fulltext :
112804.pdf (publisher's version ) (Open Access
Magneto-optics and magneto-capacitance studies of voltage-tuneable GaAs/AlGaAs quantum dots
Contains fulltext :
112792.pdf (publisher's version ) (Open Access