94 research outputs found
Fiscal measures to Reduce CO2 emissions from new passenger cars
The fuel efficiency of passenger cars is often emphasised as one of the most significant areas of action in terms of limiting the transport sector’s CO2 emission levels. This could be achieved either on the supply side through the technological development of cars, or through demand-side measures such as influencing first time buyers’ choice of car.
The aim of this article is to present a model for analysis of the demand side, more specifically the relation between the CO2 emissions from new cars and the car taxation related to new car purchases in EU. The purpose of the model is twofold. Firstly, it should be used to analyse the CO2 efficiency of the car taxation in each member state. Secondly, results from model calculations should be used to illustrate what are the possibilities for the individual member states to reduce their CO2 emissions from new cars.
The major conclusions from the study are:
It is essential to apply a tax scheme, which is directly or indirectly CO2 related in order to provide for significant reductions in the average CO2 emissions from new cars.
It is essential to differentiate the taxes in such a way that taxes for very energy effective cars are significantly lower than taxes for cars with poor energy efficiency.
Fuel tax increases provide only very small reductions of the average CO2 emissions of new cars compared to vehicle taxes.
The model is based on a revised and enhanced version of the Danish Car Choice model from 1997 combined with car characteristics, socio-economic data and car taxation data from the EU member states
Kondo physics in tunable semiconductor nanowire quantum dots
We have observed the Kondo effect in strongly coupled semiconducting nanowire
quantum dots. The devices are made from indium arsenide nanowires, grown by
molecular beam epitaxy, and contacted by titanium leads. The device
transparency can be tuned by changing the potential on a gate electrode, and
for increasing transparencies the effects dominating the transport changes from
Coulomb Blockade to Universal Conductance Fluctuations with Kondo physics
appearing in the intermediate region.Comment: 4 pages, 4 figure
Shadow epitaxy for in-situ growth of generic semiconductor/superconductor devices
Uniform, defect-free crystal interfaces and surfaces are crucial ingredients
for realizing high-performance nanoscale devices. A pertinent example is that
advances in gate-tunable and topological superconductivity using
semiconductor/superconductor electronic devices are currently built on the hard
proximity-induced superconducting gap obtained from epitaxial indium
arsenide/aluminium heterostructures. Fabrication of devices requires selective
etch processes; these exist only for InAs/Al hybrids, precluding the use of
other, potentially superior material combinations. We present a crystal growth
platform -- based on three-dimensional structuring of growth substrates --
which enables synthesis of semiconductor nanowire hybrids with in-situ
patterned superconductor shells. This platform eliminates the need for etching,
thereby enabling full freedom in choice of hybrid constituents. We realise and
characterise all the most frequently used architectures in superconducting
hybrid devices, finding increased yield and electrostatic stability compared to
etched devices, along with evidence of ballistic superconductivity. In addition
to aluminium, we present hybrid devices based on tantalum, niobium and
vanadium.
This is the submitted version of the manuscript. The accepted, peer reviewed
version is available from Advanced Materials:
http://doi.org/10.1002/adma.201908411
Previous title: Shadow lithography for in-situ growth of generic
semiconductor/superconductor device
Josephson effect in a few-hole quantum dot
We use a Ge-Si core-shell nanowire to realise a Josephson field-effect
transistor with highly transparent contacts to superconducting leads. By
changing the electric field we gain access to two distinct regimes not combined
before in a single device: In the accumulation mode the device is highly
transparent and the supercurrent is carried by multiple subbands, while near
depletion supercurrent is carried by single-particle levels of a strongly
coupled quantum dot operating in the few-hole regime. These results establish
Ge-Si nanowires as an important platform for hybrid
superconductor-semiconductor physics and Majorana fermions
Quantization of Hall Resistance at the Metallic Interface between an Oxide Insulator and SrTiO
The two-dimensional metal forming at the interface between an oxide insulator
and SrTiO3 provides new opportunities for oxide electronics. However, the
quantum Hall effect, one of the most fascinating effects of electrons confined
in two dimensions, remains underexplored at these complex oxide
heterointerfaces. Here, we report the experimental observation of quantized
Hall resistance in a SrTiO3 heterointerface based on the modulation-doped
amorphous-LaAlO/SrTiO heterostructure, which exhibits both high
electron mobility exceeding 10000 cm/Vs and low carrier density on the
order of ~10 cm. Along with unambiguous Shubnikov-de Haas
oscillations, the spacing of the quantized Hall resistance suggests that the
interface is comprised of a single quantum well with ten parallel conducting
two-dimensional subbands. This provides new insight into the electronic
structure of conducting oxide interfaces and represents an important step
towards designing and understanding advanced oxide devices
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