"Quantum Nanoelectronics" Seminars in 2011
Magnetism and Many Body Effects at the Atomic and Molecular Scale Studied with Scanning Probe Methods
Tuesday 13 December 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Markus TERNES (Max-Planck-Institute, Stuttgart, Germany) At the interface between classical and quantum mechanical description molecular magnetism has opened novel approaches in information storage, spintronics and quantum computation. In my talk I will present results on probing magnetic...
[Read More]Anderson localization in two coupled disordered chains: who wins the fast or the slow?
Tuesday 29 November 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Vladimir KRAVTSOV (International Centre for Theoretical Physics, Trieste, Italy) We solved exactly the problem of Anderson localization on two coupled disordered chains. Contrary to a frequent confusion, this problem does not reduce to solution of DMPK equation which is a ...
[Read More]Quantum phase-slips in Josephson junction chains : effects of finite size and propagating modes
Tuesday 22 November 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Gianluca RASTELLI (LPMMC, Grenoble) The macroscopic degrees of freedom in superconducting nano-devices realized with one or several Josephson junctions show a quantum behavior when they are cooled at very low temperature and when they are fabricated in electrical circuits opportunely...
[Read More]Microwave kinetic inductance detectors (MKIDs) - principles and applications
Tuesday 15 November 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Christian HOFFMANN (Institut Néel, Grenoble) A new type of superconducting detector, the Microwave Kinetic Inductance Detector, has recently drawn the attention of the low-temperature detector community. Easy fabrication, high sensitivity, low time constants and most notably the...
[Read More]Dirac fermions in Hg Te quantum wells
Tuesday 8 November 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Laurens MOLENKAMP (University of Würzburg, Germany) HgTe quantum wells have a linear band dispersion at low energies and thus mimic the Dirac Hamiltonian. Changing the well width tunes the band gap (i.e., the Dirac mass) from positive, through zero, to negative. Wells with a negative Dirac mass...
[Read More]Spin Currents and Spin Accumulations in Mesoscopic Systems
Tuesday 18 October 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Philippe JACQUOD (University of Arizona, USA) Spintronics refers to spin-based electronics, where information processing and storage are based on the spin, rather than the charge degree of freedom of the electron. This is significantly harder than to control electric charges, but holds great promises...
[Read More]Strain and nematic phase of electrons in bilayer graphene
Tuesday 11 October 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Vladimir I FALKO (Lancaster University, UK) Electrons in bilayer graphene exhibit quite unusual properties: they can be viewed as 'massive chiral fermions' with parabolic dispersion at intermediate energies and Berry phase 2π [1, 2], in contrast to monolayer graphene, where electrons are...
[Read More]The thin film Giaever transformer - vortex drag in a superconductor thin-film bilayer
Tuesday 27 September 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Gil REFAEL (Caltech Institute, Pasadena, USA) The normal-field induced superconductor-insulator transition in amorphous thin films, and the possible intervening metallic state, can be qualitatively explained within two paradigms: as vortex condensation, or as a percolation transition between...
[Read More]Anomalous dephasing in electronic Mach-Zehnder interferometers
Tuesday 20 September 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Eugene SUKHORUKOV (University of Geneva, Switzerland) Recently, Aharonov-Bohm (AB) effect in electronic Mach-Zehnder (MZ) interferometers has attracted much attention among experimental and theoretical physicists. These interferometers, for the first time experimentally realized in the group of...
[Read More]Magnetic ordering of localized moments in Dirac conductors
Tuesday 13 September 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Vadim CHEIANOV (Lancaster University, UK) Localized impurities randomly positioned on the surface of a two-dimensional material supporting excitations with massless Dirac spectrum are shown to exhibit a non-analytic dependence on 1/T at high temperature. This effect is caused by the...
[Read More]Identifications of solitons in quasi 1D electronic systems and generalisations to strong correlations in higher dimensions
Tuesday 6 September 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Serguei BRAZOVSKII (LPTMS, Orsay) We review a progress in experiments and theory, elucidating the role of microscopic solitons in quasi-1D electronic systems with a symmetry breaking. The recent interest rises from a discovery of the ferroelectric charge ordering in organic conductors,...
[Read More]Residual quasiparticles, Andreev current and photon-assisted tunneling in Coulomb blockaded normal-superconductor junctions
Tuesday 30 August 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Jukka PEKOLA (Low Temperature Laboratory, Aalto University School of Science, Finland) We are developing a precise source of electrical current I=ef, where f is the operation frequency. This device is based on normal metal superconductor (NIS) tunnel junctions. In order to suppress...
[Read More]Fractional Topological Insulators
Tuesday 12 July 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Andrei BERNEVIG (Princeton University,New Jersey, USA) In the past several years tremendous theoretical and experimental effort has been devoted to predicting and observing a new class of materials called topological insulators. These materials are non-interacting band insulators whose Bloch band...
[Read More]Quantum Optics with Superconducting Circuits: Exploring Propagating Microwave Photons
Tuesday 5 July 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Andreas WALRAFF (ETH Zurich, Switzerland) Using modern micro and nano-fabrication techniques combined with superconducting materials we realize quantum electronic circuits. We create, store, and manipulate individual microwave photons on a chip. The strong interaction of photons with superconducting...
[Read More]Entanglement and Fluctuations in Many-Body Quantum Systems
Tuesday 28 June 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Karyn LE HUR (Yale University, USA) The study of quantum many-body systems has traditionally involved the analysis of ground state and excited state energies, correlation functions, and symmetry-breaking order parameters to characterize different states of matter. Recently, there has been great...
[Read More]Quantum Phase Transition and Emergent Symmetry in Quadruple Quantum Dot System
Tuesday 21 June 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Harold BARANGER (Duke University, USA & Nanosciences Foundation Chair of Excellence) I shall discuss a system of four quantum dots designed to study the competition between three types of interactions: Heisenberg, Kondo and Ising. The competition produces a rich phase diagram containing two sharp...
[Read More]Spin Hall effect at interfaces between quantum spin Hall insulators and metals
Tuesday 14 June 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Marine GUIGOU (Université of Würzburg, Germany) The Spin Hall effect (SHE) is a physical phenomenon [Dya71] realized in nonmagnetic systems and that allows for a transverse spin current generated if an electrical charge current is driven in longitudinal direction. This can happen due to...
[Read More]Confinement-Induced Vortex Fusion and Giant Vortex States in Superconductors
Tuesday 7 June 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Dimitri RODITCHEV (Institut des Nanosciences de Paris) When put in rotation, macroscopic quantum condensates develop a very peculiar collective response: They split in a huge number of small quantum tornados - vortices - that organize in a lattice [1]. The vortex currents circulate owing to the...
[Read More]Detecting non-abelian quantum Hall state via thermal measurements
Tuesday 31 May 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Sourin DAS (University of Delhi, India) I will first discuss recent experimental attempts to detect the non-abelian nature of the nu = 5/2 quantum Hall state. Then I will talk about our theoretical proposal for detection of neutral modes which exist at the boundary of the nu = 5/2 quantum Hall state which...
[Read More]Coherent Electron-Phonon Coupling in Tailored Quantum Systems
Tuesday 24 May 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Preden ROULLEAU (Service de Physique de l'Etat Condense, CEA Saclay & ETH Zurich) The coupling between a two-level system and its environment leads to decoherence. Within the context of coherent manipulation of electronic or quasiparticle states in nanostructures, it is crucial to understand the sources of...
[Read More]Scanning tunneling spectroscopy at low temperature: Quantum Hall systems and Graphene
Tuesday 17 May 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Markus MORGENSTERN (University of Aachen, Germany) Scanning tunneling spectroscopy at low temperature is an invaluable tool to probe systems driven by local inhomogeneities. Two examples will illustrate the strength of the method. Firstly, the transition between localized and critical states of a quantum Hall...
[Read More]Josephson Current Through One Atom
Tuesday 10 May 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Cristian URBINA (Quantronics Group, CEA Saclay) Whatever the nature of a weak-link connecting two superconductors (be it a tunnel junction, a nanowire or a molecule), the Josephson effect can be described in a universal way in terms of “Andreev bound states”. These are localized superpositions of...
[Read More]The bright side of Coulomb blockade
Tuesday 3 May 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Fabien PORTIER (Laboratory of Condensed Matter Physics, CEA Saclay) The electromagnetic environment of a tunnel junction can modify the current through the junction because the sudden charge transfer associated with a tunnel event can generate photons in the environment. This dissipation process, called...
[Read More]Majorana fermions in topological insulators
Tuesday 19 April 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Carlo BEENAKKER (Leiden University, The Netherlands) Majorana fermions are spatially localized superpositions of electron and hole excitations in the middle of a superconducting energy gap. These unusual particles have been predicted to occur at the interface between a magnetic and superconducting...
[Read More]Equilibration and Transport in 1D quantum wires
Tuesday 12 April 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Tobias MICKLITZ (Freie Universitaet Berlin, Germany) We study the effect of equilibration on the transport properties of a weakly interacting one-dimensional electron system. Although equilibration in one-dimensional systems is severely suppressed due to phase-space restrictions and conservation laws, it can...
[Read More]Imaging Coulomb islands inside a quatum Hall interferometer
Tuesday 29 March 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Vincent BAYOT (Catholic University of Louvain / Nanosciences Foundation Chair of Excellence ) In the quantum Hall (QH) regime, near integer filling factors, electrons should only be transmitted through spatially separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex,...
[Read More]Majorana fermions and the superconductor proximity effect in half-metallic ferromagnets
Tuesday 8 March 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Piet BROUWER (Free University of Berlin) Because of the complete absence of minority carriers in a half metal, Andreev reflection is not possible at the interface between a half metal and an s-wave superconductor, unless the spin-rotation symmetry around the magnetization axis in the half metal is broken. In that case Andreev...
[Read More]The watt balance route towards a new definition of the kilogram
Tuesday 1 March 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Ali EICHENBERGER (Federal Office of Metrology METAS) Today, the kilogram is the last unit of the International System of Units (SI) still based on an artefact: the international prototype of the kilogram K which is kept at the Bureau International des Poids et Mesure (BIPM). The international comparisons...
[Read More]Preparation and measurement of multi-qubit entanglement
Tuesday 22 February 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Leonardo DICARLO (Delft University of Technology, The Netherlands) Entanglement has traditionally played a central role in foundational discussions of quantum mechanics. Correlation measurements between entangled quantum particles exhibit results at odds with classical behavior. With quantum mechanical predictions now...
[Read More]Using a Josephson junction for manipulating microscopic atomic dipoles
Tuesday 15 February 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Alexey USTINOV (Karlsruhe Institute of Technology, Germany) Experiments with quantized Josephson plasma oscillations in tunnel junctions display signatures of coherent coupling to individual microscopic defects acting as two-level systems (TLSs). These defects manifest themselves by avoided level crossings in microwave...
[Read More]Periodic Nanowire Structures
Tuesday 08 February 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Erik BAKKERS (Eindoven University of Technology & Delf University of Technology, Netherlands) Semiconducting nanowires offer the possibility of nearly unlimited complex bottom-up design on intrawire and interwire level, which allows for new (opto-)electronic device concepts, such as single-photon nanowire quantum dot...
[Read More]How to measure tunnelling charges without recourse to current noise?
Tuesday 1 February 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Inès SAFI (Laboratoire de Physique des Solides, Orsay) In low dimensional conductors, electronic correlations can give rise to quasi-particles carrying an electric charge q different from the elementary electron charge e. This is for instance the case for Cooper pairs, with a “charge” equal to 2e. Whereas it is...
[Read More]Localization of preformed Cooper pairs in highly disordered superconducting films
Tuesday 25 January 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Claude CHAPELIER (CEA-INAC/SPSMS/LATEQS) I will present a study combining tunnelling spectroscopy and point-contact Andreev spectroscopy on disordered superconducting indium oxide films. These samples are in the vicinity of the metal-insulator Anderson transition. Tunneling spectroscopy highlights a rather unusual...
[Read More]Quantum glasses – frustration and collective behavior at zero temperature
Tuesday 18 January 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Markus MÜLLER (ICTP Trieste) Glasses are strongly interacting and disordered systems, which develop rather unusual amorphous order at low temperatures. The phase transition into the glass state is marked by the loss of ergodicity, i.e., the localization in phase space due to the emergence of high energy...
[Read More]Nanotechnology with graphene, nanotubes and diamond-like carbon
Tuesday 11 January 2011 at 3pm Room "Rémy Lemaire" K 223 (1st floor) Building K, Institut Néel / CNRS Andrea FERRARI (Department of Engineering, University of Cambridge) Carbon based materials play a major role in today's science and technology. Carbon is a very versatile element, which can crystallise in the form of diamond or graphite. Great excitement has followed the discovery of new forms of carbon, including fullerenes, nanotubes and single...
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