The QuNES research fields embrace mesoscopic physics, quantum nano-electronics, and surface science. The main topics are electronic properties of 2D materials such as graphene and transition metal dichalcogenides, topological orders in Dirac materials, quantum thermodynamics, hybrid superconducting devices, many-body physics in semiconductor quantum dots and point contacts, and strongly disordered superconductors. The originality of the QuNES team is to combine quantum transport measurements with local probe measurements, using scanning tunneling microscopy and spectroscopy, atomic force microscopy, and scanning gate microscopy, at very low temperature, in ultra high vacuum, and under high magnetic fields.
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Electronic properties of 2D materials |
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Topological phases in Dirac materials |
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Thermodynamics of quantum devices |
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Kondo cloud extension around quantum dots |
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Strongly disordered superconductors |
Pierre Mallet, Jean-Yves Veuillen
Isolated hydrogen atoms absorbed on graphene are predicted to induce magnetic moments. Here we demonstrate, by using STM complemented by first-principles calculations, that the adsorption of a single H atom on graphene induces a magnetic moment characterized by a 20 meV spin-split state at the Fermi energy. By using the STM tip to manipulate H atoms with atomic precision, it is possible to tailor the magnetism of selected graphene regions.
Collaborations :
Universidad Autonoma de Madrid
Publications :
Atomic-scale control of graphene magnetism by using hydrogen atoms, H. Gonzalez-Herrero, J.M. Gomez-Rodriguez, P. Mallet, M. Moaied, J.J. Palacios, C. Salgado, M.M. Ugeda, J.-Y. Veuillen, F. Yndurain, and I. Brihuega, Science 352, 437 (2016)
We performed STM/STS measurements to map the band onsets and the electronic bandgap of 2D semi-conducting TMDs such as WSe2 or MoSe2 deposited on Gr/SiC by mechanical exfoliation or MBE. We analyzed how these electronic properties are tuned by the substrate and by static disorder such as step edges, atomic scale defects, charged impurities, and boundaries.
Collaborations :
LNCMI Grenoble
SPINTEC Grenoble
Publications :
Scanning tunneling spectroscopy of van der Waals graphene/semiconductor interfaces: absence of Fermi level pinning, T. Le Quang, V. Cherkez, K. Nogajewski, M. Potemski, M.T. Dau, M. Jamet, P. Mallet, and J.-Y. Veuillen, 2D Materials 4, 035019 (2017)
Band-bending induced by charged defects and edges of atomically thin transition metal dichalcogenide films, T. Le Quang, K. Nogajewski, M. Potemski, M.T. Dau, M. Jamet, P. Mallet, and J.-Y. Veuillen, 2D Materials 5, 035034 (2018)
Benjamin Sacépé, Hermann Sellier
Alexis Coissard, Corentin Deprez, Marco Guerra, Hadrien Vignaud
We unveiled a new interaction-induced topological phase in the zero-th Landau level of graphene. This phase is insulating in the bulk and exhibits a pair of spin-filtered, helical edge channels. It emerges under moderate perpendicular magnetic field when graphene is placed in proximity to a high-k dielectric substrate. In this work we demonstrate a remarkably robust quantum spin Hall effect that withstands up to 110 K over micron-long distances, which opens a new avenue for spintronics and topological superconductivity. More information
Publications :
Helical quantum Hall phase in graphene on SrTiO3, L. Veyrat, C. Déprez, A. Coissard, X. Li, F. Gay, K. Watanabe, T. Taniguchi, Z. V. Han, B. A. Piot, H. Sellier, and B. Sacépé, Science 367, 781 (2020)
Fundings :
ERC grant QUEST (2015-2020)
The absence of energy gap in graphene at zero magnetic field makes the fabrication of nanostructures difficult using metallic surface gates. In large magnetic fields however, the formation of Landau levels creates gaps in the spectrum, and the conducting edge channels follow the electrostatic potential of the gates. In this regime, quantum point contacts can be realized to control the number of channels transmitted through the device. The graphene flake can also be encapsulated between two boro-nitride flakes to boost its electron mobility. In such an heterostructure, the four-fold degeneracy of the Landau levels is lifted, and the fractional quantum Hall effect has been observed. Thanks to this unprecedented graphene quality, we achieved a precise control of the transmitted current through a quantum point contact, and more complex devices can now be studied, such as quantum Hall interferometers. More information
Publications :
Tunable transmission of quantum Hall edge channels with full degeneracy lifting in split-gated graphene devices, K. Zimmermann, A. Jordan, F. Gay, K. Watanabe, T. Taniguchi, Z. Han, V. Bouchiat, H. Sellier, and B. Sacépé, Nature Communications 8, 14983 (2017)
Low-magnetic-field regime of a gate-defined constriction in high-mobility graphene, L. Veyrat, A. Jordan, K. Zimmermann, F. Gay, K. Watanabe, T. Taniguchi, H. Sellier, and B. Sacépé, Nano Letters 19, 635 (2019)
Fundings :
ERC grant QUEST (2015-2020)
Clemens Winkelmann, Hervé Courtois
Danial Majidi, Efe Gumus
Thermal transport in quantum devices is an interesting and yet vastly unexplored topic of research. We carried out thermal transport measurements through a single electron transistor (SET) where theory predicts a violation of some fundamental laws of physics. A thermal gradient is applied across the SET by cooling or heating the source (left) with a biased NIS junction while the drain (right) is thermalized to bath temperature. By measuring the temperature of the source as a function of the applied gate voltage using another NIS junction, we observed a periodic modulation of the heat conductance through the SET that shows a strong deviation from the usual Wiedemann-Franz law relating the charge and heat conductances.
Publications :
Thermal Conductance of a Single-Electron Transistor, B. Dutta, J. T. Peltonen, D. S. Antonenko, M. Meschke, M. A. Skvortsov, B. Kubala, J. König, C. B. Winkelmann, H. Courtois, and J. P. Pekola, Phys. Rev. Lett. 119, 077701 (2017)
Fundings :
Nanosciences Foundation Chair of Excellence of J. P. Pekola
LANEF PhD fellowship of Efe Gumus
Marie Curie ITN project QuESTech
Electron transport through quantum dots coupled to superconducting leads shows a sharp conductance onset when a QD orbital level crosses one of the superconducting coherence peaks. Using individual gold nanoparticles connected to electromigrated aluminum leads, we showed that the hybridization of the QD levels with the leads is strongly enhanced by the divergent density of states at the superconducting gap edge. This result highlights the importance of cotunneling effects in spectroscopies with superconducting probes. In a regime where current is transported through a single level and driven by an ac gate voltage, we demonstrated single-electron-turnstile operation with a very narrow energy distribution and a higher immunity to nonequilibrium quasiparticles of the leads.
Publications :
Probing hybridization of a single energy level coupled to superconducting leads, D. M. T. van Zanten, F. Balestro, H. Courtois, and C. B. Winkelmann, Phys. Rev. B 92, 184501 (2015)
Single Quantum Level Electron Turnstile, D. M. T. van Zanten, D. M. Basko, I. M. Khaymovich, J. P. Pekola, H. Courtois, and C. B. Winkelmann, Phys. Rev. Lett. 116, 166801 (2016)
Fundings :
Nanosciences Foundation Chair of Excellence of J. P. Pekola
LANEF PhD fellowship of Alvaro Garcia-Corral
Marie Curie ITN project QuESTech
Hermann Sellier, Benjamin Sacépé
Diego Fossion
Gate-defined semiconductor quantum dots represent promising objects for quantum engineering. This project investigates the spatial extension of the many-body Kondo state that develops around these quantum dots at very low temperature. This Kondo cloud is a highly entangled state that could be used to coherently couple remote quantum dots distant by several microns. In this project, we employ scanning gate microscopy, a combined transport and scanning probe experiment, to measure the spatial extension of the Kondo cloud and to probe the Kondo-mediated coherent coupling between two quantum dots.
Collaborations :
Serge Florens (NEEL, team ThQC)
Louis Jansen, Marc Sanquer (CEA/INAC, Grenoble, France)
Dominique Mailly, Ulf Gennser (CNRS/C2N, Palaiseau, France)
Benoit Hackens, Vincent Bayot (UCL/IMCN, Louvain, Belgium)
Fundings :
ANR KONEX (2019-2023) KONdo-cloud EXtension around quantum dots
Electron-electron interactions in QPCs give rise to conductance anomalies below the first quantized plateau at 2e²/h, called 0.7 anomaly and zero-bias anomaly. Using scanning gate microscopy, we observed a repetitive splitting of the zero-bias anomaly when the tip approaches the QPC and tune the length of the quasi-1D channel, indicating the formation of a localized electron chain within the constriction, a sort of 1D Wigner crystal. Scanning gate interferometry close to the QPC revealed a phase shift of the electron interference in the bias range of the zero-bias anomaly, interpreted as a signature of localized states in the constriction with Kondo effect. We also introduced a new technique called Thermoelectric Scanning Gate Microscopy to probe quantum phenomena by measuring the thermoelectric voltage across the QPC instead of the conductance. This technique revealed a new phase shift in the tip-induced interference at very low conductance.
Publications :
Wigner and Kondo physics in Quantum Point Contacts revealed by Scanning Gate Microscopy, B. Brun, F. Martins, S. Faniel, B. Hackens, G. Bachelier, A. Cavanna, C. Ulysse, A. Ouerghi, U. Gennser, D. Mailly, S. Huant, V. Bayot, M. Sanquer, and H. Sellier, Nature Communications 5, 4290 (2014)
Electron Phase Shift at the Zero-Bias Anomaly of Quantum Point Contacts, B. Brun, F. Martins, S. Faniel, B. Hackens, A. Cavanna, C. Ulysse, A. Ouerghi, U. Gennser, D. Mailly, P. Simon, S. Huant, V. Bayot, M. Sanquer, and H. Sellier, Phys. Rev. Lett. 116, 136801 (2016)
Interference features in scanning gate conductance maps of quantum point contacts with disorder, K. Kolasinski, B. Szafran, B. Brun, and H. Sellier, Phys. Rev. B 94, 075301 (2016)
Thermoelectric scanning-gate interferometry on a quantum point contact, B. Brun, F. Martins, S. Faniel, A. Cavanna, C. Ulysse, A. Ouerghi, U. Gennser, D. Mailly, P. Simon, S. Huant, M. Sanquer, H. Sellier, V. Bayot, and B. Hackens, Phys. Rev. Applied 11, 034069 (2019)
Benjamin Sacépé
The interplay between disorder and superconductivity is a fundamental problem of condensed matter physics. Upon increasing disorder or magnetic field it is indeed possible to induce in a thin superconducting film a continuous quantum phase transition from a superconducting state to an insulating state led by the localization of electron pairs. Such zero-temperature transition, which involves Cooper pairs as charge carriers, provides a prototypical system to address the physics of the quantum localization of interacting bosons in disordered media. In this field we mainly focused our research on thin films of amorphous indium oxide, which exhibits a sharp superconductor-to-insulator transition. On the superconducting side of the transition, we have performed in close collaboration with C. Chapelier at INAC, the pioneering mK-STM spectroscopy study of the superconducting gap. Our work has demonstrated that Cooper pairs are not suppressed at the critical disorder but persist in insulators forming localized electron bound pairs. Beyond the critical disorder or critical magnetic field, the insulator that terminates superconductivity is attracting considerable interest due to mounting evidences that the charge carriers in it are electron pairs. In collaboration with D. Shahar from the Weizmann Institute of Science, we have performed magneto-transport studies on thin films. These experiments on insulators focus on the electron-phonon coupling in non-linear transport and on the possible many-body localization of charge carriers in this peculiar insulating state. More information
Position type: Permanent positions
Contact: Poizat Jean-Philippe -
Experimental development of novel quantum devices in quantum nanoelectronics
Tenure track position
NB Candidates must contact jean-philippe.poizat@neel.cnrs.fr or a research scientist at Institut Néel ahead of the deadline in order to build a research project.
Important dates :
– Deadline to apply : May 22nd, 2023
– Interview : betwxeen June, 5th, and July, 13th, 2023
– Position entry : December, 1rst, 2023 at the latest
Official advertisement of the position on the UGA website
Application instructions – application file
Chaires de Professeur Junior (CPJ) are a new way of recruiting on the basis of research and teaching projects. They are tenure track positions. At the end of the contract, between 3 and 6 years, and after evaluation of the scientific value and professional aptitude of the agent by an evaluation commission, the candidate can be promoted to a permanent position as a Professor.
Research profile
The study of the electronic properties of quantum circuits is an important and historical research axis for the Néel Institute. Néel Institute is involved in many programs in the field of quantum technologies, including the ERC Synergy QuCube, as well as the RobustSuperQ and PRESQUILE projects of the PEPR Quantum Technologies, which mainly address the development of semiconductor and superconducting spin qubits with a view to their scaling up.
The University of Grenoble Alpes (UGA) plays a leading role in the development of Grenoble’s very rich quantum community. With the experimental research activity of this CPJ, UGA will strengthen its position in quantum technologies by developing innovative quantum platforms based on emerging materials and concepts. Without being exhaustive, research axes have been identified, some of which are complementary to those explored in the framework of the Quantum PEPR:
– Hybrid superconductor/semiconductor or graphene nanostructures or two-dimensional materials, for which topological protection against qubit decoherence is predicted theoretically, but not demonstrated experimentally.
– The manipulation and detection of a single electron wave packet based on a two-dimensional electron gas of very high mobility, which would allow access to the unexplored territory where the frequencies become comparable to the internal electronic characteristic time scales.
– The local and time-resolved thermodynamic study of quantum devices, which will allow understanding and specifying the strong constraints imposed by the entropy generation in any irreversible logic operation.
The recruited researcher will be supported by a funding of 200 k€ from the ANR and an additional funding providing by UGA.
Teaching profile
Teaching assignments consist of 96 hours per year.
The strengthening of human resources is also a strong and necessary axis of the national strategy for quantum technology to ensure innovation, attractiveness and competitiveness of the industrial and research ecosystem. In order to meet the growing need for skills in quantum technologies, the national project QuanTEdu-France, led by the University of Grenoble Alpes, brings together a consortium of 21 academic institutions. The central objective of QuanTEdu-France is to implement concrete actions, from pre-university training to doctoral training, in initial and continuing education, in partnership with professional training and industrial players, while actively participating in the digital transition of training in higher education institutions. The CPJ will thus be able to invest, in connection with the project coordinator, in awareness-raising activities and the development of new UEs, as well as in the creation of a “quantum technologies” practical work platform.
Person in charge: Hermann SELLIER
Students & Post-docs & CDD
Jean-Yves VEUILLEN
Personnel Chercheur - CNRS
Jean-Yves.Veuillen@neel.cnrs.fr
Phone: 04 76 88 74 61
Office: D-414
Johannes HOFER
Personnel Chercheur - UGA
Phone: 04 76 88 12 24
Office: D-308
Referent: Clemens WINKELMANN
David PERCONTE
Personnel Chercheur - CNRS
Office: D-313
Referent: Benjamin SACEPE
Anjan Kumar GUPTA
Personnel Chercheur - inst. Science Mohali - Inde
anjan-kumar.gupta@neel.cnrs.fr
Referent: Hervé COURTOIS