Activity Report 2010 - CNRS

when compared, for example, to the
prototype of the US “competitor” project
MUSIC (to be installed at the CSO 10-m
sub-mm observatory in Mauna Kea, and
being developed years before NIKA).
MUSIC involves laboratories like Caltech,
JPL, University of Santa Barbara and
others.
A second week technical time on the
IRAM telescope was approved in October
2010. The sensitivity of the LEKID array
improved by a factor of three compared
to the first run in 2009, verifying that
NIKA is rapidly approaching the final
target of sensitivity.
This second run was a total success,
allowing the observation, for example, of
a large number of extended sources.
Please read the corresponding Highlight
at the end of this report for further
information.
group at Université Catholique de
Louvain-Louvain-la-Neuve. The upgrading
of the SGM tool is the main activity of a
shared PhD student hired by the
foundation (Peng LIU).
InGaAs/InAlAs heterostructures are
grown by Molecular Beam Epitaxy at
IEMN (Lille) and patterned by e-beam
lithography at UCL for obtaining Quantum
Rings. The results are interpreted thanks
to quantum conductance simulations
performed at IMEP (Grenoble) by Marco
Pala.
SCIENTIFIC REPORT
Scanning
gate
Nanoelectronics
Chair of Excellence 2007: Vincent BAYOT
Coordinators: Hervé COURTOIS and
Serge HUANT (Institut Néel).
In the framework of Vincent Bayot’s Chair
of Excellence, two major results were
obtained by Scanning Gate Microscopy
(SGM) :
a theoretical understanding of SGM
images in the coherent regime of
transport both in the presence of
defects and weak magnetic field
the discovery of Coulomb islands in a
Quantum Hall (QH) interferometer.
In the latter, SGM was used for obtaining
a spatially resolved investigation of
electron transport inside an
interferometer formed by an
InGaAs/InAlAs Quantum Ring (QR),
driven in the integer QH regime. The
pseudo Aharonov–Bohm (AB) period was
associated with a specific Coulomb island
formed by edge state loops enclosing a
hill or a valley in the potential. Each
active Coulomb island was located
precisely inside the QR by tuning the
magnetic field and imaging the spatial
shift of Coulomb resonances by means of
SGM.
The (SGM) uses the electrically polarized
tip of a low-temperature AFM to scan
above a semiconductor device and record
the change in conductance at point (x,y),
induced by the tip located at that point.
The SGM tool is being developed jointly
at the Institut Néel by the group of Serge
HUANT and Hermann SELLIER in
collaboration with Vincent BAYOT and his
Fig. 3: Vincent BAYOT, Chair of Excellence in
2007
Please read the corresponding Highlight
at the end of this report for further
information.
Superconducting
Nanostructures
Chair of Excellence 2009: John R.
KIRTLEY
Coordinator: Klaus HASSELBACH (Institut
Néel).
John R. KIRTLEY is one of the world’s
leading experts on Josephson junction
devices and superconductivity. The
project is aimed at the study of the
physical properties of high quality
superconducting films and their
integration into quantum nano-devices.
First results have been obtained in 2010.
As a matter of fact the core of a
conventional tunnel barrier is formed of
oxidized nano-grains with fluctuating
electric charges at their surface. These
charges are suspected of causing
decoherence of superconducting Qbits.
Thanks to molecular beam epitaxy a
charge-free junction was achieved by
growing epitaxial layers of Rhenium /
Sapphire / Rhenium (Re/Al 2 O 3 /Re), giving
a superconducting Qubit. The layers have
been grown successfully by the group of
B. Gilles (SIMAP), on sapphire substrates,
and characterized by STM, AFM and X-ray
diffraction.
FURTHER READING
Nat. Commun. 1:39, (2010)
Imaging Coulomb islands in a quantum
Hall interferometer
Nanotechnology, 20, 264021 (2009)
Scanning gate microscopy of quantum
rings: effects of an external magnetic
field and of charged defects.
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