Service de Physique de l'Etat Condensé

SPEC PhD subjects

Dernière mise à jour : 29-03-2017

23 sujets IRAMIS/SPEC

• Climate modelling

• Mesoscopic physics

• Radiation-matter interactions

• Soft matter and complex fluids

• Solid state physics, surfaces and interfaces

 

Improving stochastic generators of climate/financial data using the underlying dynamics

SL-DRF-17-0773

Research field : Climate modelling
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Davide Faranda

Bérengère DUBRULLE

Starting date : 01-09-2017

Contact :

Davide Faranda

CEA - DRF/LSCE (DSM)

0169085232

Thesis supervisor :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

More : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=dfaranda

More : http://iramis.cea.fr/spec/sphynx/

More : http://iramis.cea.fr/Pisp/berengere.dubrulle/index.html

Forecasting and understanding the behavior of complex systems such as turbulence, climate and finance is a challenging task. To tackle this problem, various tools have been developed using dynamical systems theory, statistical mechanics or stochastic fits to the data using e.g. Auto Regressive Moving Average (ARMA) processes. Such approaches are however limited by the presence of multiple metastable states, that can trap the system in non-equilibrium quasi-steady state, or attract the trajectories in the phase space.



Examples of such meta-stable states are blocked and zonal flows in the mid-latitude atmospheric dynamics, crises and period of growth in economy and finance. At present time, there is no general theory that allows the prediction of the plausibility of, time-life of or dynamics around such meta-stable states. Improved description of the system dynamics of the trajectories in the presence of metastable states have been recently obtained by splitting the original time-series in short subsamples that obey basic ARMA processes [1,2,3]. In those papers, several indicators have been derived to analyze the data. They provide information about the number of degrees of freedom active in the systems and the probability of jumps towards other metastable states.

The goal of this PhD study is to go one step further, and use this method to forecast the behavior of complex systems. The PhD candidate will construct stochastic generators of plausible turbulent, climate and financial fields by including the underlying dynamical properties as derived by the previous indicators. She/he will assess the quality of the generated fields by comparing the results on real data. During the PhD thesis, the candidate will acquire competences in statistics, fundamental physics, climate dynamics and finance. She/he will develop numerical tools and models with the analysis of time-series.

The Phd Thesis require a good knowledge of stochastic processes and therefore a background on applied statistics or theoretical physics. The candidate should know how to use statistical analysis software as R, Matlab and/or Python. She/he should have a good level of understanding of English language, to work in an international environment.



[1] Davide Faranda, Gabriele Messori and Pascal Yiou. Dynamical proxies of North Atlantic predictability and extremes. Accepted for publication in Scientific Reports, 2017.

[2] Guillaume Nevo, Nikki Vercauteren, Amandine Kaiser, Berengere Dubrulle, Davide Faranda. A statistical-mechanical approach to study the hydrodynamic stability of stably stratified atmospheric boundary layer. Submitted, 2017.

[3] Davide Faranda and Dimitri Defrance: A wavelet-based-approach to detect climate change on the coherent and turbulent component of the atmospheric circulation. Earth System Dynamics, 7 517-523, 2016.

Manipulation of the quantum state of individual superconducting excitations in nanowires

SL-DRF-17-0427

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Quantronique (GQ)

Saclay

Contact :

Marcelo GOFFMAN

Starting date : 01-09-2017

Contact :

Marcelo GOFFMAN

CEA - DRF/IRAMIS/SPEC/GQ

0169085529

Thesis supervisor :

Marcelo GOFFMAN

CEA - DRF/IRAMIS/SPEC/GQ

0169085529

More : http://iramis.cea.fr/Pisp/marcelo.goffman/

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

Electrons in superconductors form Cooper pairs that cannot be probed individually because they are delocalized and overlapping. However, localized states appear at weak links between superconducting electrodes. Using atomic contacts as a weak link, we performed the spectroscopy of these localized states [1] and demonstrated the quantum manipulation of a localized Cooper pair [2].

During the internship, we plan to develop similar experiments with InAs semiconducting nanowires. Longer coherence times are expected, and, because of the strong spin-orbit coupling in InAs, one should also be able to manipulate the spin of localized electrons.



The student 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. Bretheau et al., “Exciting Andreev pairs in a superconducting atomic contact”

Nature 499, 312 (2013). arXiv:1305.4091

[2] C. Janvier et al., “Coherent manipulation of Andreev states in superconducting atomic contacts”

Science 349, 1199 (2015), arXiv:1509.03961

Out-of-equilibrium thermoelectric transport in quantum conductors

SL-DRF-17-0097

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Geneviève FLEURY

Jean-Louis PICHARD

Starting date : 01-10-2017

Contact :

Geneviève FLEURY

CEA - DRF/IRAMIS/SPEC/GMT

0169087347

Thesis supervisor :

Jean-Louis PICHARD

CEA - DRF/IRAMIS/SPEC/GMT

0169087236

More : http://iramis.cea.fr/spec/Pisp/genevieve.fleury/

More : http://iramis.cea.fr/spec/GMT/

Seebeck and Peltier thermoelectric effects provide an eco-friendly way of converting heat into electricity and vice-versa. Thus it is possible with the Seebeck effect to harvest waste heat for producing electricity. Conversely, the Peltier effect enables local cooling of a device by investing electrical power. For a long time, thermoelectric conversion has been limited by a poor efficiency and therefore, practical applications have till date remained rare. Interest in the field has been recently rekindled by the discovery of new promising materials, by progress in nanostructuration, and by the growing societal concern about energy issues.

The purpose of this theoretical PhD thesis is to study analytically and numerically thermoelectric conversion in low-dimensional mesoscopic systems. We will consider the regime far from equilibrium where important thermoelectric effects are expected. In particular, we will investigate systems under dynamic time-dependent forcing. From a methodological standpoint, we will use the numerical tools and the analytical formalism developed at CEA-Grenoble (X. Waintal's team) for the study of (out-of-equilibrium) time-resolved quantum transport (see https://kwant-project.org/). We will adapt it to the case of thermoelectric transport and apply it to various systems (quantum dots, quantum point contacts, nanowires…).

Single electron detection for electron quantum optics and electron flying qubits

SL-DRF-17-0107

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Nano-Electronique (GNE)

Saclay

Contact :

Christian Glattli

Starting date : 01-10-2017

Contact :

Christian Glattli

CEA - DRF/IRAMIS/SPEC/GNE

0607060501

Thesis supervisor :

-

More : http://iramis.cea.fr/Pisp/24/christian.glattli.html

More : http://nanoelectronics.wikidot.com/general

Our goal is to realize basic quantum operations using the information coded by the presence or not of a single electron (a flying qubit) propagating in a quantum conductor. This requires single electron sources to initialize the flying qubit, quantum gates in the form of electron interferometers to perform quantum operation, and single charge detectors for single shot readout. In this “electron quantum optics” approach, single electron sources, the electronic analog of single Photons sources, are already available where single electrons are created in the form of levitons. Present ballistic conductors used can also routinely provide quantum gates in the form of electron beam splitters and electron interferometers. The present Ph-D project is to realize the missing brick: the single electron detector which would allow for a full single shot quantum operation. Bolometric or charge detection schemes will be explored.

Electronic Mach Zehnder in graphene

SL-DRF-17-0036

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Nano-Electronique (GNE)

Saclay

Contact :

Preden Roulleau

Christian Glattli

Starting date : 01-10-2017

Contact :

Preden Roulleau

CEA - DRF/IRAMIS/SPEC/GNE

0169087311

Thesis supervisor :

Christian Glattli

CEA - DRF/IRAMIS/SPEC/GNE

0607060501

More : http://iramis.cea.fr/Pisp/preden.roulleau/

More : http://nanoelectronics.wikidot.com/

More : http://iramis.cea.fr/spec/index.php

Quantum computing is based on the manipulation of quantum bits (qubits) to enhance the efficiency of information processing. In solid-state systems, two approaches have been explored:

• static qubits, coupled to quantum buses used for manipulation and information transmission,

• flying qubits which are mobile qubits propagating in quantum circuits for further manipulation.



Flying qubits research led to the recent emergence of the field of electron quantum optics, where electrons play the role of photons in quantum optic like experiments. This has recently led to the development of electronic quantum interferometry as well as single electron sources. As of yet, such experiments have only been successfully implemented in semi-conductor heterostructures cooled at extremely low temperatures. Realizing electron quantum optics experiments in graphene, an inexpensive material showing a high degree of quantum coherence even at moderately low temperatures, would be a strong evidence that quantum computing in graphene is within reach.

One of the most elementary building blocks necessary to perform electron quantum optics experiments is the electron beam splitter, which is the electronic analog of a beam splitter for light. However, the usual scheme for electron beam splitters in semi-conductor heterostructures is not available in graphene because of its gapless band structure. I propose a breakthrough in this direction where pn junction plays the role of electron beam splitter [1]. Based on this, an electronic Mach Zehnder interferometer will be studied to understand the quantum coherence properties of graphene. This PhD proposal is part of the ERC starting grant COHEGRAPH (2016).





[1] Shot noise generated by graphene p-n junctions in the quantum Hall effect regime N. Kumada, F. D. Parmentier, H. Hibino, D. C. Glattli, and P. Roulleau , Nature Communications

Quantum Phase Slips in NanoWires

SL-DRF-17-0430

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Quantronique (GQ)

Saclay

Contact :

Philippe JOYEZ

Starting date : 01-09-2016

Contact :

Philippe JOYEZ

CEA - DRF/IRAMIS/SPEC/GQ

0169087444

Thesis supervisor :

Philippe JOYEZ

CEA - DRF/IRAMIS/SPEC/GQ

0169087444

More : http://iramis.cea.fr/Phocea/Membres/Annuaire/index.php?uid=pj

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

The celebrated Josephson junction is so far the only known non-linear non-dissipative electronic component. These key properties place it at the heart of essentially all superconducting electronic devices: SQUIDS magnetometers, Josephson Volt standards but also the recently developed quantum information processing circuits or quantum-limited amplifier circuits.

The present thesis aims at testing the practical feasibility and actual properties of a second non-linear non-dissipative superconducting component which was proposed by Mooij and Nazarov [1] nearly a decade ago. This new component is called a Quantum Phase Slip Junction (QPSJ). It consists of a very thin superconducting wire which is predicted to behave as the exact quantum dual of the Josephson junction. Such duality means that the equations describing the QPSJ and the Josephson junction are formally identical save for charge and phase exchanging roles. In other words, where a Josephson junction coherently superposes many states differing by the number of Cooper pairs having tunneled through the barrier, a QPSJ coherently superposes many states differing by the number of 2p phase windings along the wire, which can be seen as a superposition of various number of flux quanta having tunneled across the wire. Would such a QPSJ component become actually available, it would be a genuine breakthrough. In particular, it should enable the realization of an experiment dual to the celebrated AC Josephson effect that would be emblematic of QPSJ physics: Instead of establishing a metrological link between the Volt and the second, this dual experiment would link the Ampere to the second. Likewise, a whole new range of high impedance superconducting circuits (which are presently downright antinomic) would become feasible. This would unquestionably open up a new era for the whole field of superconducting circuits.

Since the proposal of QPSJ came to light, a handful of experiments have investigated the physics of QPSJ, partially confirming the predictions [2,3], but raising more questions than they brought answers. In particular the very basic prediction of a periodic charge modulation in QPSJs is lacking a clear-cut confirmation [4]. The main goal of this thesis is to perform the experiment proposed by Hriscu and Nazarov [5], aiming specifically at testing this charge modulation.



[1] Mooij and Nazarov, Nat. Phys. 2, 169 (2006).

[2] Astafiev et al., Nature 484, 355 (2012),

[3] Peltonen et al. Phys. Rev. B 88, 220506(R) (2013)

[4] Hongisto and Zorin, Phys. Rev. Lett. 108, 097001 (2012)

[5] Hriscu and Nazarov, Phys. Rev. Lett. 106, 077004 (2011)

Photophysics of Hot electrons transfer between plasmonic nanoparticles and molecular adsorbates

SL-DRF-17-0272

Research field : Radiation-matter interactions
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Celine FIORINI

Starting date : 01-10-2017

Contact :

Celine FIORINI

CEA - DRF/IRAMIS/SPEC/LEPO

0169086238

Thesis supervisor :

Celine FIORINI

CEA - DRF/IRAMIS/SPEC/LEPO

0169086238

More : http://iramis.cea.fr/Pisp/celine.fiorini/

More : http://iramis.cea.fr/spec/LEPO/

Beyond the enhancement of photophysical processes (Raman spectroscopy, frequency conversion, fluorescence …) optically excited plasmonic nanoparticles were recently demonstrated to be interestingly used to activate chemical transformations directly and very locally on their surfaces. This opens up many opportunities in the field of selective chemical synthesis, the controlled fabrication of hybrid nanostructures, phototherapy, photocatalysis ... The identification of the parameters enabling to control these chemical reactions induced by plasmons is currently focusing the attention of a large community. The difficulty is to distinguish between various physical phenomena likely to take place, ie (1) the localized heating resulting from the thermalization (electron-phonon interaction) of the hot electrons generated by exciting a NP at its resonance or, (2) direct charge transfer effects between hot electrons and nearby molecules.



The aim of the thesis is to study the mechanisms of hot electron transfer between an excited metal particle with plasmon resonance and a molecular adsorbate placed in proximity, in the absence of solvent (dry way) following a multiphotonic excitation. To this end, we will take advantage of the joint use of complementary characterization means implemented and mastered at CEA / SPEC-LEPO: 2-photon luminescence microscopy (TPL), which has recently been the subject of important developments in the laboratory and photoelectron emission microscopy (PEEM), for which CEA / SPEC-LEPO is a specialist.

Dissipation, cascades and singularities in turbulence

SL-DRF-17-0173

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Bérengère DUBRULLE

Starting date : 01-10-2017

Contact :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

Thesis supervisor :

Bérengère DUBRULLE

CNRS - DRF/IRAMIS/SPEC/SPHYNX

0169087247

More : http://iramis.cea.fr/Pisp/berengere.dubrulle/index.html

More : http://iramis.cea.fr/spec/sphynx/

Many phenomena in nature involve motion of viscous flows, which are widely believed to be described by Navier-Stokes equations (NSE). These equations are used for instance in numerical simulations of flows in astrophysics, climate or aeronautics. These equations are the cornerstones of many physical and engineering sciences, and are routinely used in numerical simulations. From a mathematical point of view, however, it is still unclear whether the Navier-Stokes equations are a well-posed problem in three dimensions, i.e. whether their solutions remain regular over sufficient large time or develop singularities.

Historically, the search for singularities in NSE was initiated by Leray who introduced the notion of weak solutions (i.e. in the sense of distribution). This notion was used to prove that the mathematical singular set has a one-dimensional Haussdorff measure equals to zero in space-time. Therefore, if these singularities exist, they must be extremely localized events in space and time. This makes their direct detection an outstanding problem. For some times, the best suggestive evidence of their existence was provided by the observation that the energy dissipation rate in turbulent flows tends to a constant at large Reynolds numbers This observation is at the core of the 1941 Kolmogorov theory of turbulence, and was interpreted by Onsager as the signature of singularities with local scaling exponent $h=1/3$. Later, it was conjectured that the singularities are organized into a multifractal set. Analysis of measurements of 3D numerical or 1D experimental velocity fields showed that the data are compatible with the multifractal picture, with a most probable $h$ close to $1/3$. However, this analysis could not reveal any information on the space-time statistics of (possible) singularities.



A major breakthrough was achieved when Duchon and Robert performed a detailed energy balance for weak solutions of INSE, and compute the contribution stemming from an eventual lack of smoothness. They show that it can be lumped into a single term, that quantifies the "inertial" energy dissipation, i.e. the energy dissipated by non-viscous means.

The purpose of this thesis is to test these mathematical results in a numerical turbulent swirling flow to infer properties of the energy dissipation in a turbulent flow.

Thermoelectric phenomena in ferrofluids

SL-DRF-17-0010

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

SAWAKO NAKAMAE

Starting date : 01-10-2017

Contact :

SAWAKO NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Thesis supervisor :

SAWAKO NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

More : http://iramis.cea.fr/Pisp/sawako.nakamae/

More : http://iramis.cea.fr/spec/SPHYNX

3D study of destabilized flows

SL-DRF-17-0528

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Gilbert ZALCZER

Romain Monchaux

Starting date :

Contact :

Gilbert ZALCZER

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169083164

Thesis supervisor :

Romain Monchaux

ENSTA Paristech - IMSIA

01.69.31.97.66

More : http://iramis.cea.fr/spec/Phocea/Membres/Annuaire/index.php?uid=zalczer

More : http://iramis.cea.fr/spec/SPHYNX/

Liquid lows under solicitation have always been a subject of fascination, owing to the diversity of the observed effects. A simple flow, at low speed, get more and more complicated when the speed increases, goes through different transitions before becoming turbulent. Owing to newly developed techniques in the domains of fast imaging and fast beam control, it seems possible to get "instantaneous" views of the 3 components of the velocity all over the bulk, even for the supra-laminar domain. We already performed bulk measurements of 2D velocities but have not been able to reconstruct even the laminar flow pattern. Preliminary experiments suggest the possibility of measuring also the third component of the velocity. The experimental work will be first to merge these elements into an operational setup and then study the different flows occurring.

Optical measurements of dissipation and energy fluxes in turbulent flows

SL-DRF-17-0878

Research field : Soft matter and complex fluids
Location :

Service de Physique de l'Etat Condensé (SPEC)

Systèmes Physiques Hors-équilibre, hYdrodynamique, éNergie et compleXes (SPHYNX)

Saclay

Contact :

Sébastien AUMAÎTRE

Starting date : 01-10-2017

Contact :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

Thesis supervisor :

Sébastien AUMAÎTRE

CEA - DRF/IRAMIS/SPEC/SPHYNX

01 69 08 74 37

More : http://iramis.cea.fr/Pisp/sebastien.aumaitre/

More : http://iramis.cea.fr/spec/SPHYNX/

The aim of this proposal is the study of power fluctuations in turbulent flow. The usual theoretical approaches have shown that the stationarity of the flow, implying the balance of the power injected large scales with the power dissipated at small scales, constrains the power spectrum of the velocity. However, one needs to go beyond to explain the complexity and the intermittency of turbulent flow. One can consider the statistical properties of the fluctuations of powers involved in turbulent flow. Especially one can explore the correlations implied by the stationarity on the fluctuations of injected and dissipated power and theirs consequences on the structure of the flow. The challenge is to estimate the fluctuations of dissipated power resolved in time. To do so, we would like to develop an innovative optical technics implying diffusive wave spectroscopy and ultra-fast image acquisition. This technics will be complemented by usual measurement technics in order to estimate simultaneously the injected power and to probe the structure of the flow.

New electronic states in single crystals and thin films of iridates

SL-DRF-17-0120

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Jean-Baptiste MOUSSY

Dorothée COLSON

Starting date : 01-10-2017

Contact :

Jean-Baptiste MOUSSY

CEA - DRF/IRAMIS/SPEC/LNO

01-69-08-92-00

Thesis supervisor :

Dorothée COLSON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 73 14

More : http://iramis.cea.fr/spec/Pisp/jean-baptiste.moussy/

More : http://iramis.cea.fr/spec/LNO/

More : http://iramis.cea.fr/spec/Pisp/dorothee.colson/

Iridates (e.g. Sr2IrO4, Sr3Ir2O7 ...) have recently attracted attention due to the presence of a strong spin-orbit coupling and strong electronic interactions that give rise to original physical properties such as, the high critical temperature superconductivity or the state of topological insulator. Especially, the identification of a topological phase in these oxides should allow exploring new ways to manipulate the spin of electrons, a key point for applications in spintronics.

The aim of this thesis project is to study the emergence of Mott insulators, magnetic and topological properties in single crystals, single layers and heterostructures of iridates. More precisely, the objectives of the thesis will be to synthesize new compounds of the iridates family (e.g.Sr3Ir2O7) in the form of single crystals and thin films to explore their electronic properties (new topological phases, new Mott insulators, etc).For the development of single crystals, the self-flux method will be chosen. Sr3Ir2O7 crystals of pure compound will be synthesized and electron doping will be achieved through cationic substitutions (for example: Sr/La). Then, the crystals will be characterized by different techniques: X-ray diffraction, electron microprobe and magnetic measurements (SQUID, VSM magnetometry). For thin films, we will use a new ultrahigh vacuum growth technique developed in the laboratory: the pulsed laser deposition (PLD) method with a laser beamworking in the nanosecond or femtosecond regime. PLD is a well-known technique for the epitaxial growth of oxide thin films (cuprates, manganites, ferrites ...), which is based on the ablation by a laser beam of the target of the material to be deposited on a monocrystalline substrate. A peculiar attention will be given to the structural and physical properties of oxide thin films by using in situ electron diffraction (RHEED), photoemission spectroscopy (XPS/UPS), or ex situ techniques such as near-field microscopy (AFM), magnetism (SQUID,VSM). The electronic properties of samples (crystals and films) will then be studied in collaboration with the LPS-Orsay, including electrical measurements and the quantum spin Hall effect, which is the signature of a topological state.

Characterization and control of charged ferroelectric domain walls

SL-DRF-17-0220

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS)

Saclay

Contact :

Nicholas BARRETT

Starting date : 01-10-2017

Contact :

Nicholas BARRETT

CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

Thesis supervisor :

Nicholas BARRETT

CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

More : http://iramis.cea.fr/Pisp/nick.barrett/

More : http://iramis.cea.fr/spec/lensis/

Ferroic oxides are materials displaying one or more order parameters: ferroelectric, ferroelastic and/or magnetic. They possess intrinsic domains separated by domain walls which can have completely different physical properties compared to those of the bulk material. Exploring these properties might allow envisaging domain walls as the active element of the materials properties.

In a ferroelectric, charged domain walls could be a new paradigm for post-CMOS electronics since they can be considered as nanometric metallic conductors in a highly insulating dielectric medium. The thesis work will focus on how these walls respond to external electric or mechanical stress.

The student will use photoelectron and low energy electron spectromicroscopy to study the chemical and electronic surface structure of domain walls with nanometric spatial resolution. Dedicated sample-holders will allow the operando analysis under electric or mechanical stress. The samples will be provided by the Institut de Chimie Moléculaire et Matériaux d'Orsay. The experiments will be done in collaboration with the UMPhys CNRS/Thalès and the Institute of Nanotechnologies of Lyon.

Water photo-electrolysis assisted by an internal potential

SL-DRF-17-0046

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Hélène MAGNAN

Antoine BARBIER

Starting date : 01-10-2017

Contact :

Hélène MAGNAN

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 04

Thesis supervisor :

Antoine BARBIER

CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

More : http://iramis.cea.fr/Pisp/helene.magnan/

More : http://iramis.cea.fr/spec/LNO/

More : http://iramis.cea.fr/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=1996&id_unit=0&id_groupe=196

Photo-electrolysis is a very seductive solution to produce hydrogen using solar energy. Metal oxides are promising candidates for photoanode, but simple oxides present some limiting factors which can explain their relatively low efficiency for hydrogen production.



In this experimental thesis, we propose to use the spontaneous electric field of a ferroelectric compound to better separate photogenerated charges within the photoanode. In this study, we will investigate model samples (epitaxial thin films prepared by molecular beam epitaxy) and will study the influence of the electric polarization orientation with respect to the surface of the electrode (upward, downward, unpolarized, multi domains) on the photo-electrochemical efficiency. Moreover in order to understand the exact role of electrical polarization, we will measure the lifetime of the photogenerated charges and the electronic structure for the different state of polarization using synchrotron radiation. This thesis work is in the framework of long term research project where the CEA is associated with synchrotron SOLEIL, and University of Bourgogne for a modelisation of the systems.

Interface Dzyaloshinskii-Moriya interaction physics.

SL-DRF-17-0478

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Cyrille BARRETEAU

Starting date : 01-10-2017

Contact :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Thesis supervisor :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

More : http://iramis.cea.fr/Pisp/cyrille.barreteau/

More : http://iramis.cea.fr/spec/GMT

The progress of the science and technology of the magnetism of matter is since the 1930’s largely driven by the reduction of dimensions. The physical properties of magnetic material are very dependent on the size and the shape of the sample. The magnetic characteristic of a surface, a thin film, a wire or a nanoparticle are indeed very different and also very far from the one of the bulk. The possibility to grow ultrathin films is at the origin of the discovery of Giant Magnetoresistance which gave rise to the spintronic and its discoverers A. Fert and P. Grunberg were awarded the 2007 Nobel Prize in Physics. Since a few years a magnetic interaction has attracted attention of researchers: The Dzyaloshinskii-Moriya (DMI) interface interaction. This interaction is well known in bulk since many years but its study in magnetic ultrathin films deposited on a nonmagnetic substrate is very recent. It is at the origin of very specific non-collinear magnetic structures such as skyrmions which are fascinating objects that the scientific community hopes to be able to manipulate with a view to create magnetic devices such as memories. However, the fundamental mechanisms at the origin of the interface DMI are still not well understood and the modelling at the atomic scale (electronic structure calculations) is mandatory. In this thesis we propose to use (and develop) electronic structure codes to calculate the interface DMI on systems that will be characterized experimentally. The future PhD student will integrate a theory & modeling team with a long experience in the electronic structure, magnetism and transport properties of nanostructures.

In operando study of ferrite - perovskite multiferroic encapsulated microstructures

SL-DRF-17-0177

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Antoine BARBIER

Starting date : 01-10-2017

Contact :

Antoine BARBIER

CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

Thesis supervisor :

Antoine BARBIER

CEA - DRF/IRAMIS/SPEC/LNO

01.69.08.39.23

More : http://iramis.cea.fr/Pisp/137/antoine.barbier.html

More : http://iramis.cea.fr/spec/LNO/

More : http://iramis.cea.fr/spec/Phocea/Vie_des_labos/Ast/ast_visu.php?id_ast=2545&id_unit=9&id_groupe=179

Perovskite ferroelectric oxides coupled with magnetic ferrites belong to the new class of artificial multiferroic materials. Their high potential for applications in spintronics and energy conversion makes their study a challenging topic. The nature of the coupling, especially during operation under an external field, remains largely unexplored. The proposed thesis work consists of a close collaboration between CEA and SOLEIL synchrotron (HERMES beamline); the student guidance will be equally shared between both institutions. The ferrite inclusions in a single crystalline perovskite film will be realized at CEA by molecular beam epitaxy assisted by an atomic oxygen plasma or thermal treatment. The behaviour of these inclusions under functioning conditions will be examined using the most advanced synchrotron radiations techniques and in particular spectromicroscopy, absorption, X-ray diffraction and magnetic dichroism, respectively on beamlines HERMES, DIFFABS and DEIMOS in a close collaborative approach. The student will acquire skills in ultra-high vacuum techniques, molecular beam epitaxy, magnetometry as well as in the above mentioned state of the art synchrotron radiation techniques.

Tunable multicomponent supramolecular magnetic self-assembly for spintronics

SL-DRF-17-0350

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Fabien SILLY

Starting date : 01-10-2015

Contact :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Thesis supervisor :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

More : http://iramis.cea.fr/Pisp/fabien.silly/index.html

More : http://iramis.cea.fr/spec/LEPO/

The autonomous ordering and assembly of molecules on atomically well-defined surfaces is an important technique for evolving applications in nanotechnology. The objective of this PhD project is to create tunable open molecular architectures to control the ordering of magnetic nano-objects on metal surfaces. The idea is to use experimental parameters to switch to one magnetic structure to another. These structures will be characterized using scanning tunneling microscopy in ultra-high vacuum and spin polarized scanning tunneling spectroscopy. Theses tunable nanostructures are model candidates to study magnetism at the nanometer scale.

Giant tetragonality, local octahedral distortions and chemical switching of the ferroelectric polarization in strained PbTiZrO3 and BiFeO3 thin films studied by X-ray photoelectron diffraction

SL-DRF-17-0336

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Etude des NanoStructures et Imagerie de Surface (LENSIS)

Saclay

Contact :

Nicholas BARRETT

Starting date : 01-10-2016

Contact :

Nicholas BARRETT

CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

Thesis supervisor :

Nicholas BARRETT

CEA - DRF/IRAMIS/SPEC/LENSIS

0169083272

More : http://iramis.cea.fr/Pisp/nick.barrett/

More : http://iramis.cea.fr/spec/lensis/

The fundamental property of ferroelectric (FE) materials is the electrically switchable spontaneous polarization below the Curie temperature. The chemical environment can switch the ferroelectric state, the oxygen partial pressure for example can induce preferential polarization orientation.



X-ray Photoelectron Diffraction combines the chemical sensitivity of core level photoemission with local order sensitivity around the emitting atom and is ideally suited to measure the three dimensional surface distortions in the atomic structure of epitaxial FE films.



The aim is to study and to chemically control the local atomic distortions in the giant pseudo-tetragonal phase of BiFeO3 films grown on substrates with high misfit strain. The huge polarization values, if switchable, would be of great interest in a variety of piezoelectric and ferroelectric applications. However, the very strong pseudo-tetragonality might shift the coercive field beyond breakdown making device manufacture impossible. Chemical switching of the polarization offers an alternative route to reversibly control the FE polarization.



Thin film samples will be grown at the National Institute of Materials Physics (Magurele, Romania) and at the UMPhys CNRS/Thalès. The XPD experimental results will be interpreted thanks to simulations in collaboration with the University of Goias (Brazil).

Theoretical study of graphene electrodes for Molecular Electronics

SL-DRF-17-0258

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Yannick DAPPE

Starting date : 01-10-2017

Contact :

Yannick DAPPE

CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

Thesis supervisor :

Yannick DAPPE

CNRS - DRF/IRAMIS/SPEC/GMT

+33 (0)1 69 08 84 46

More : http://iramis.cea.fr/spec/Pisp/yannick.dappe/

More : http://iramis.cea.fr/spec/GMT/

Molecular Electronics constitute nowadays a very active field of research, either for fundamental aspects in these new systems which allow exploring new Physics at the atomic scale, than for the possible applications in terms of innovative electronic devices. Indeed, beyond the ability to reproduce silicon based components (diodes, transistors, …), molecules can also bring new types of electric response due to the great number of quantum degrees of freedom, which are tunable according to the considered molecule. Indeed, the quantum nature of these objects as well as the new associated functionalities open fascinating perspectives to build future electronics. Consequently, those new researches have led to important developments in the field of Molecular Electronics, in particular regarding the control and manipulation of electronic transport through a molecular junction. Most of the molecular junctions are based on molecules connected to metallic electrodes (gold, platinum, silver…). However, it has been demonstrated in several occasions that the connection between molecule and electrode has a non negligible influence on the electric conductance of the system. In that manner, recent developments have proposed to make use of new materials like graphene, which is really well-known for its fantastic electric conduction properties, as electrodes for molecular junctions. Hence, it has been observed that the connection to a graphene electrode allows to significantly increase the junction conductance for long molecular chains, and therefore to reduce the energetic cost of such junction.

The main objective of this PhD lies in this frame by the theoretical study of asymmetric molecular junctions based on graphene or MoS2, as well as the study of molecular wires lifted off a surface using a STM tip. By using Density Functional Theory (DFT), we will determine the equilibrium configuration of the molecular junction and the corresponding electronic properties, before in a second time to calculate the electronic transport from the obtained structures, using a Keldysh-Green formalism. The purpose will be to understand the mechanism of conductance increase with respect to classical junctions, and to compare them to existing experimental results. The different expected behaviorsin those systems allow to study the Physics of electronic transport at the atomic scale, and could be exploited for the conception of new devices at the single molecule scale.

Magnetic properties of differently-shaped metal nanocrystals

SL-DRF-17-0342

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire d'Electronique et nanoPhotonique Organique (LEPO)

Saclay

Contact :

Fabien SILLY

Starting date :

Contact :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

Thesis supervisor :

Fabien SILLY

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 80 19

More : http://iramis.cea.fr/Pisp/fabien.silly/index.html

More : http://iramis.cea.fr/spec/LEPO/

The structure and shape of metal nanocrystals govern their magnetic properties at the nanometer scale. The objective of this PhD project is to grow differently-shaped metal nanocrystal and investigate their magnetic properties. These structures will be characterized using scanning tunneling microscopy in ultra-high vacuum, spin polarized scanning tunneling spectroscopy and synchrotron spectroscopy. Theses tunable nanostructures are model candidates to study magnetism and observe new magnetic phenomena at the nanometer scale.

Electronic, magnetic and transport properties of two-dimensional organo-metallic molecular networks.

SL-DRF-17-0487

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Cyrille BARRETEAU

Starting date : 01-10-2017

Contact :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

Thesis supervisor :

Cyrille BARRETEAU

CEA - DRF/IRAMIS/SPEC/GMT

+33(0)1 69 08 38 56

More : http://iramis.cea.fr/Pisp/cyrille.barreteau/

More : http://iramis.cea.fr/spec/GMT

Since the discovery (or rather the exfoliation) of a monolayer of carbon called graphene the number of studies on two-dimensional materials has exploded. It was shown that a large number of materials can exist in monolayers, however, in most cases the synthesis is obtained by deposition on a substrate which generates strain and defects that alter the properties of the intrinsic material. Another alternative recently proposed by chemists consists in growing molecular networks at the liquid/liquid (or liquid/air) interface which allows overcoming the perturbation issues generated by the substrate. The network can be deposited a posteriori on a substrate. The properties of such systems are basically mostly unknown and a modelling work is mandatory to provide guidance to the experimentalists in order to define the most appropriate molecules. Preliminary calculations have shown the extreme versatility of these networks which physical characteristics vary significantly as a function of their structure, chemical composition or electric charge etc. In this thesis we propose to perform a theoretical and modelling effort to elucidate the electronic, magnetic and transport properties of these two-dimensional molecular networks. A strong collaboration with experimental teams will greatly help the definition of the most adequate systems for future applications. The future PhD student will integrate a theory & modeling team with a long experience in the electronic structure, magnetism and transport properties of nanostructures.

Local magnetic microscopy by magnetoresistive nanosensor integration

SL-DRF-17-0244

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Aurélie Solignac

Myriam PANNETIER-LECOEUR

Starting date : 01-10-2016

Contact :

Aurélie Solignac

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 95 40

Thesis supervisor :

Myriam PANNETIER-LECOEUR

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 74 10

More : http://iramis.cea.fr/spec/Pisp/aurelie.solignac/

More : http://iramis.cea.fr/spec/LNO/

The use of giant magnetoresistance effect allows developing very sensitive magnetic sensors able to detect magnetic field of the order of nT/vHz. However, to detect magnetic objects with very small dimensions and in a local way, a reduction of the sensor size has to be realized. The use of nanofabrication tools such as electronic lithography allows fabricating active structures down to 50nm sizes. Firstly, the effect of the size reduction on the sensors performances in terms of magnetoresistance and of noise will be studied.

Secondly, the nanometric size sensors developed will be integrated in AFM (Atomic Force Microscope) tip type structures. This integration will allow combining a nanometric magnetic sensors and a scanning probe microscope like AFM, creating an ultra-sensitive and quantitative magnetic microscope.

The PhD aim will be to develop this microscope and to test it, initially, on magnetic structures as domain walls. Then other magnetic objects, for example biologic or steel could be studied by beneficiating from the spatial resolution and the sensitivity at low frequency of the microscope.

Finally, an implementation of the microscope will be the addition of an alternative magnetic field to allow the characterization in an original way of the magnetic surface susceptibility.

Biomagnetic signal recordings with spin electronics sensors

SL-DRF-17-0262

Research field : Solid state physics, surfaces and interfaces
Location :

Service de Physique de l'Etat Condensé (SPEC)

Laboratoire Nano-Magnétisme et Oxydes (LNO)

Saclay

Contact :

Myriam PANNETIER-LECOEUR

Starting date : 01-10-2017

Contact :

Myriam PANNETIER-LECOEUR

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 74 10

Thesis supervisor :

Myriam PANNETIER-LECOEUR

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 74 10

More : http://iramis.cea.fr/Pisp/myriam.pannetier-lecoeur/

More : http://iramis.cea.fr/spec/LEPO/

More : http://www.magnetrodes.com

Spin electronics, which exhibits transport properties depending on the magnetic field, has been used at SPEC to build sensors dedicated to the detection of magnetic signature of the information transmission in excitable cells (cardiac cells and neurons). We have though detected the cardiac magnetic signal thanks to Giant Magneto Resistance (GMR)-based sensors [Appl. Phys. Lett. 2011].



To increase the signal acquisition speed, it will be necessary to enhance the sensors sensitivity by the use of Magnetic Tunnel Junctions (MTJs), which can exhibit magnetoresistance ratio up to 250% at room temperature (vs 10% for GMR).



The PhD will develop devices based on MTJs for the detection of neuronal activity at various scales (from few neurons up to tens of thousands of neurons at the scalp surface). The MTJs stack will be realized on our new thin film deposition system. The probes, fabricated in the laboratory, will be tested in the SPEC magnetically shielded room, to evaluate their intrinsic performances, and then applied to in vivo neuronal recordings and whole brain measurements on Magneto-Encephalography (MEG, passive magnetic recordings at the surface of the scalp) in collaboration with Neurospin laboratory.



These magnetic recordings will allow a multi-scale imaging of neuronal currents, in particular to investigate from the cell level to the brain scale low frequency components of the neuronal signal (1/f noise), already observed in electro-encephalography and MEG recordings but not yet fully understood.

 

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