Nanoelectronics Group

Post-doc positions

We are looking for excellent and highly motivated post-doc candidateS for the following projects:

 

  • Anyons on demand (2 years contract - ANR FullyQuantum 2018):

The Nanoelectronics Group currently has an opening for a Post-Doctoral Position on our experiment on Anyonic statistics with Fractional Levitons in the Fractional Quantum Hall Effect regime.
The candidate will lead a presently running experiment on the project on abelian and non-abelian statististics using on-demand anyon sources based on levitons in the FQHE regime. Through electronic Hong Ou Mandel interferences, the time control would permit an unprecedented measurement of the quantum statistical angle of e/3 or e/5 anyons or non-abelian anyons.
References:

  • Nature 502, 659–663 (2013) dx.doi.org/10.1038/nature12713

  • Nature 514, 603–607 (2014) DOI: 10.1038/nature13821

  • A Josephson relation for fractionally charged anyons, Science 363, pp. 846-849 (2019) DOI: 10.1126/science.aau3539 (preprint)

contact: christian.glattli@cea.fr


  • Thermal conductance of many-body quantum Hall states of graphene (2 years contract- ERC QuaHQ, 2019):

The goal of this project is to explore quantum transport of heat in new states of matter arising in ultra-clean graphene under high magnetic fields, using ultra-sensitive electronic noise measurements. This project is funded by the European Research Council (ERC-StG-2018 805080 QUAHQ).

We have an open position (starting February 2019) for a highly talented postdoctoral collaborator, with comprehensive skills in nanofabrication (in particular van der Waals heterostructures), low noise measurements, and cryogenics.

contact: François Parmentier


  • Single-charge detection for electron quantum optics (2 years post doc)

The present state of the art is to read out electron quantum optics experiments by a measurement of the average transfer probability of electrons into output ports (i.e. current) and the current noise. This project will break new ground, developing techniques for the detection of the individual single-electron wave packet.

For levitons the project will explore the use of a single-leviton induced electron-avalanche in a graphene constriction in the QHE regime, biases near breakdown, which will be detected by a measurable noise . Presently the QHE breakdown mechanisms in high-mobility h-BN graphene is unknown. The project will advance the state of the art understanding of its mechanisms and signatures, notably its ability to detect ultra-small (≤ 1 pA) DC current or short-time current pulses (yet explored in GaAs).

contact: Preden Roulleau



PhD & Intern positions

We are looking for motivated students for the following projects:

  • Electron tunneling time and its fluctuations (Master 2 Internship & PhD proposal)

    Master 2 Internship, about 3-6 months, available for starting from January 2020,

    PhD position, 3 years funded by CEA CFR thesis program, available for starting in October 2020

    contact: Carles Altimiras

               Challenging our classical intuition, quantum tunneling has fascinated physicists for decades. Very soon after its discovery it raised the question of how much time do particles spend under the classically forbidden barrier. Despite its simplicity, such a question is ill defined in terms of quantum observables and does not admit a single answer, thus triggering over the past decades a bunch of different definitions corresponding to different (thought) scenarios.

              We will address this question from the perspective of a well-defined observable: that is, measuring how the number of particles residing within the classically forbidden barrier fluctuates in time [1]. The experiment will be performed on a 2D electron gas, where electrostatically coupled metallic gates are used to generate and tune the potential barrier upon which a single channel of electrons is scattered. The presence of tunneling electrons within the barrier will trigger mirror-charge fluctuations on the gates which we will collect and detect using state-of-the-art RF techniques in cryogenic environments mastered in the group.

              The long term goal of the PhD thesis will be to understand and experimentally characterize the interplay between electron-electron interactions and the tunneling time fluctuations. Indeed, recent theory [2] has predicted that the tunneling time fluctuations play a key role in the impurity-driven quantum phase transition of interacting 1D fermions [3] and the equivalent dissipation-driven quantum phase transition of quantum point contacts [4].

    References:

    [1] Pedersen, van Langen, and Büttiker, Phys. Rev. B 57, 1838 (1998)

    [2] Altimiras, Portier & Joyez, Phys. Rev. X 6, 031002 (2016)

    [3] Kane & Fisher, PRB 46, 15233 (1992)

    [4] Anthore et al., Phys. Rev. X 8, 031075 (2018)

  • The Hong Ou Mandel experiment in graphene

    Master 2 internship (3-6 months) paid by an ERC starting Grant

    PhD position, 3 years

contact: preden.roulleau@cea.fr

Historically, the Hong Ou Mandel experiment has been performed to get time-domain information on the photon wave packets: it was a direct way to measure the time width of single photon wave packets. The lack of quadratic detectors to perform time auto-correlation at so low input level led them to consider the second order coherence  by colliding the idler and signal photons generated by parametric down-conversion of a laser source on a beam splitter. Indeed, the interference of the two indistinguishable particles makes the particle detection statistics dependent on their wavefunction overlap. After N0 experiments, the particle number fluctuation is , where the plus sign holds for bosons, the minus sign holds for fermions,  is the time delay between particles and  is their velocity. For non-overlapping states at large , the fluctuations of two particles independently partitioned is found. For zero delay (full overlap), the bosonic bunching doubles the noise whereas the fermionic exclusion makes it vanish. Hong–Ou–Mandel experiments are now standard in quantum optics. With the use of electronic beamsplitters in GaAs/AlGaAs, d.c. and a.c. voltage sources have shown anti-bunching [1,2].

Recently we have shown that it was possible to mimic these beam splitters in graphene and to obtain Mach Zehnder interferometers with record visibility of 88% [3]. Based on this, we propose an original Hong Ou Mandel geometry to probe for the first time the fermion statistics in graphene.

During this training period, the student will join a running experiment and realize numerical simulation of electron collision in graphene.

This proposal is part of the ERC starting grant COHEGRAPH (2016).

 

[1] J. Dubois, T. Jullien, F. Portier,  P. Roche, A. Cavanna, Y. Jin, W. Wegscheider,  P. Roulleau,  & D. C.Glattli ,  Nature 502, 659-663 (2013)

[2] E. Bocquillon et al., Science 339, 1054 (2013)

[3] Coherent manipulation of the valley in graphene, M. Jo, P. Brasseur, A. Assouline, W. Dumnernpanich, P. Roche, D.C. Glattli,  N. Kumada,  F.D. Parmentier,  and P. Roulleau, in preparation (2019)

 
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