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PhD subjects

5 sujets IRAMIS

Dernière mise à jour : 06-06-2020


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• Mesoscopic physics

 

Light-emissive self-organized molecular metamaterials

SL-DRF-20-0528

Research field : Mesoscopic physics
Location :

Service de Physique de l’Etat Condensé

Laboratoire d’Electronique et nanoPhotonique Organique

Saclay

Contact :

Fabrice CHARRA

Starting date : 01-10-2020

Contact :

Fabrice CHARRA
CEA - DRF/IRAMIS

+33/169089722

Thesis supervisor :

Fabrice CHARRA
CEA - DRF/IRAMIS

+33/169089722

Personal web page : http://iramis.cea.fr/Pisp/144/fabrice.charra.html

Laboratory link : http://iramis.cea.fr/Phocea/Vie_des_labos/Ast/ast_groupe.php?id_groupe=154

More : http://www.ipcm.fr/article670.html

The progresses in photonic technologies require the independent control of the propagation of the phase and the energy of light. This is possible using hyperbolic metamaterials, an ultimate case of birefringence with ordinary and extraordinary dielectric constants of opposite sign.



Self-organized molecular systems offer a route to the realization of such media since they can embed various p-conjugated mesogens amenable to form a large variety of structures with record-breaking optical anisotropy.



Our objective is to develop an innovative self-organized (macro) molecular system comprising fluorescent moieties in order to combine hyperbolic dispersion with light emission or optical gain. Beyond the compensation of the intrinsic losses of metamaterials we target the realization of innovative light-emitting devices by embedding the source in the bulk of the metamaterial, whereas most current realizations involve complex nanoscale combinations of different emissive and birefringent media.



The thesis will include the structural and optical characterization of the materials obtained, the analysis of their hyperbolic characteristics, and their integration into model optical devices. The design, synthesis and chemical characterization of the materials will be carried out by another laboratory as part of a collaboration.

Anyonic statistics of toplogical e/3 and e/5 fractionally charged excitations in the Quantum Hall Effect regime

SL-DRF-20-0704

Research field : Mesoscopic physics
Location :

Service de Physique de l’Etat Condensé

Groupe Nano-Electronique

Saclay

Contact :

D. Christian GLATTLI

Starting date : 01-10-2020

Contact :

D. Christian GLATTLI
CEA - DRF/IRAMIS/SPEC/GNE

0169087243

Thesis supervisor :

D. Christian GLATTLI
CEA - DRF/IRAMIS/SPEC/GNE

0169087243

Personal web page : http://iramis.cea.fr/Pisp/24/christian.glattli.html

Laboratory link : http://iramis.cea.fr/spec/gne/

More : https://nanoelectronicsgroup.com/

In some quantum matter states, the current may remarkably be transported by carriers that bear a fraction e* of the elementary electron charge. This is the case for the Fractional quantum Hall effect (FQHE) that happens in two-dimensional systems at low temperature under a high perpendicular magnetic field. When the number of magnetic flux in units of h/e is a fraction of the number of electrons, a dissipationless current flows along the edges of the sample and is carried by anyons with fractional charge e/3, e/5, e/7, etc. These fractional excitations are believed to be anyons intermediate between fermions and bosons. However the evidence of anyonic statistics is still lacking.

We propose an original approach based on the manipulation of anyons by microwave photons as recently demonstrated in the group (Science 2019). The idea is to realize a single anyon source similar to the one developed for electrons based on Levitons (Nature 2013, Nature 2014). Combining 2 such sources would allow the 2-anyon interference required to evidence the anyonic statistics.

The thesis work will require the realization of the on-demand single anyon source using microwave Lorentzian pulses at ultra-low temperature in 14 Tesla magnetic field. The characterization will include electronic quantum noise measurements and coincidence measurements thanks to a new single charge detector



1] A Josephson relation for fractionally charged anyons, M. Kapfer, P. Roulleau, I. Farrer, D. Ritchie and D. C. Glattli ( SCIENCE (2019) https://doi.org/10.1126/science.aau3539 )



[2] Minimal-excitation states for electron quantum optics using levitons, J. Dubois, T. Jullien, F. Portier, P. Roche, A. Cavanna, Y. Jin, W. Wegscheider, P. Roulleau and D. C. Glattli, NATURE 502, 659-663 (2013)



[3] Quantum tomography of an electron, T. Jullien, P. Roulleau, B. Roche, A. Cavanna, Y. Jin and D. C. Glattli, Nature 514, 603–607 ( 2014)



Electron tunneling time and its fluctuations

SL-DRF-20-0484

Research field : Mesoscopic physics
Location :

Service de Physique de l’Etat Condensé

Groupe Nano-Electronique

Saclay

Contact :

Carles ALTIMIRAS

Patrice ROCHE

Starting date : 01-10-2020

Contact :

Carles ALTIMIRAS
CEA - DRF/IRAMIS/SPEC/GNE

01 69 08 72 16

Thesis supervisor :

Patrice ROCHE
CEA - DRF/IRAMIS/SPEC/GNE

0169087216

Personal web page : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=caltimir

Laboratory link : http://iramis.cea.fr/spec/GNE/

More : https://nanoelectronicsgroup.com/

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.



Following a proposal by Büttiker & collaborators [1], we will address this question from the perspective of a well-defined observable: that is, measuring the spectrum of time fluctuations of the number of particles residing within the classically forbidden barrier. The idea is to exploit semiconducting 2D electron gases where electrostatically coupled metallic gates are used to generate the electrostatic potential barrier upon which the electrons are scattered. Moreover, we will equally use them to collect the mirror influence-charges fluctuating in response to the tunneling electrons residing within the electrostatic barrier. Despite its conceptual simplicity, implementing such a scenario is a formidable task since it demands collecting a tiny radiofrequency (RF) signal emitted by a huge output-impedance source in a sub-Kelvin (dilution) refrigerator. We will build upon the group’s expertise in RF design and ultra-low noise measurements in cryogenic environments in order to overcome this challenge, notably implementing recently developed high impedance RF matching circuits [2] allowing us to efficiently collect the signal into a RF detection chain.



In a second step, we will perform similar measurements in experimental conditions where electron-electron interactions strongly modify the transport properties across the barrier. Notably a metal/insulator quantum phase transition is driven by such interactions when a 1D wire is interrupted by an impurity, mimicking Tomonaga-Lutinger liquid dynamics [3]. We wish to investigate this physics from the original perspective of the electron tunneling time, as put forward by a recent theoretical finding [4].



The student will participate to the radiofrequency design of the samples, to their fabrication in a clean-room environment, and to their measurement exploiting low noise measurement techniques both in the near DC and the few GHz range. He will become familiar with sub-Kelvin cryogenic techniques as well.



References:

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

[2] Rolland et al., https://arxiv.org/abs/1810.06217

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

[4] Altimiras, Portier and Joyez, Phys. Rev. X 6, 031002 (2016)

“Fine structure” of a superconducting circuit: Manipulation of the spin of a single electron

SL-DRF-20-0093

Research field : Mesoscopic physics
Location :

Service de Physique de l’Etat Condensé

Groupe Quantronique

Saclay

Contact :

Hugues POTHIER

Starting date : 01-10-2020

Contact :

Hugues POTHIER
CEA - DRF/IRAMIS/SPEC/GQ

01 69 08 55 29

Thesis supervisor :

Hugues POTHIER
CEA - DRF/IRAMIS/SPEC/GQ

01 69 08 55 29

Personal web page : http://iramis.cea.fr/spec/Pres/Quantro/static/people/hugues-pothier/index.html

Laboratory link : http://iramis.cea.fr/spec/GQ/

More : http://iramis.cea.fr/spec/Pres/Quantro/static/index.html

We design and fabricate superconducting circuits that are ruled by the laws of quantum mechanics. In this internship, we propose to carry out experiments aiming at the quantum coherent manipulation of the spin of a single quasiparticle excitation.



In practice, we use semiconducting nanowires covered with a superconducting shell. The shell is removed in a small section of the nanowire, giving rise to a spectrum of quantized electronic levels in the superconductor-free section. We have recently shown that, due to the spin-orbit interaction in the semiconductor, this spectrum presents a fine structure similar to that of electronic states in atoms [1]. During the internship proposed before the thesis, the quantum manipulation of the spin of a single electron in the nanowire will be realized using circuit quantum electrodynamics techniques. This will give access to the lifetime and quantum coherence time of the states.



We also plan to test the recent prediction of a magnetic-field-driven phase transition in nanowires fully covered with a superconductor [2]. A topological phase supporting Majorana fermions could be reached, and revealed by the spectroscopy of the circuit.



We look for a strongly motivated student having a good understanding of quantum physics. She/he will be integrated in an active research group on quantum electronics and get acquainted with advanced concepts of quantum mechanics and superconductivity. He/she will also learn several experimental techniques: low temperatures, low-noise and microwave measurements, and nanofabrication.



[1] L. Tosi et al., “Spin-Orbit Splitting of Andreev States Revealed by Microwave Spectroscopy”, Phys. Rev. X 9, 011010 (2019).

[2] R. Lutchyn et al., “Topological superconductivity in full shell proximitized nanowires” arXiv :1809.05512 (2018).



Electrodynamics of Disordered Superconductors, for the development of Quantum Phase Slip junction devices.

SL-DRF-20-1139

Research field : Mesoscopic physics
Location :

Service de Physique de l’Etat Condensé

Groupe Quantronique

Saclay

Contact :

Hélène Le SUEUR

Daniel ESTEVE

Starting date :

Contact :

Hélène Le SUEUR
CNRS - SPEC

01 69 08 38 88

Thesis supervisor :

Daniel ESTEVE
CEA - DRF/IRAMIS/SPEC/GQ

0169085529

Personal web page : http://iramis.cea.fr/Pisp/daniel.esteve/

Laboratory link : http://iramis.cea.fr/spec/GQ

The Quantronics group at SPEC is performing research in fundamental solid state physics at very low temperature, and in particular in quantum electronics. One present goal of our team is to elucidate the last missing ingredient of mesoscopic superconductivity: the Quantum Phase Slip Junction.



A Quantum phase slip junction (QPSJ) consisting of very thin disordered superconducting wire is predicted to behave as a non-linear nondissipative capacitor, and to constitute an exact quantum dual of the well know and widely used Josephson junction. The availability of QPSJ would open a broad range of new possibilities for quantum circuit engineering.



By making nanowire resonators in order to realize QPSJ, we have evidenced a strong coupling of the resonator to surrounding charged Two Level Systems, an order of magnitude larger than what is expected from standard dipole / electric field coupling. We have shown this phenomenon is present in several superconductors who have in common their high inductance (high disorder). We have proposed recently [leSueur18] a new universal mechanism to explain this strong coupling, through mesoscopic fluctuations of the kinetic inductance. The general goal of the PhD detailed below is to fully characterize this mechanism.

 

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