Service de Physique de l'Etat Condensé

SPEC PhD subjects

Dernière mise à jour : 15-12-2017

15 sujets IRAMIS/SPEC

• Mesoscopic physics

• Soft matter and complex fluids

• Solid state physics, surfaces and interfaces

 

Out-of-equilibrium thermoelectric transport in quantum conductors

SL-DRF-18-0459

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Mésocopie Modélisation et Thermoélectricité (GMT)

Saclay

Contact :

Geneviève FLEURY

Alexander SMOGUNOV

Starting date : 01-10-2017

Contact :

Geneviève FLEURY

CEA - DRF/IRAMIS/SPEC/GMT

0169087347

Thesis supervisor :

Alexander SMOGUNOV

CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Personal web page : http://iramis.cea.fr/spec/Pisp/genevieve.fleury/

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

This subject is now receiving CEA funding as a "flagship" topic. The selection of the candidatures received will be made at the beginning of spring 2018.



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…).

Quantum heat transport in graphene Van der Waals heterostructures

SL-DRF-18-0412

Research field : Mesoscopic physics
Location :

Service de Physique de l'Etat Condensé (SPEC)

Groupe Nano-Electronique (GNE)

Saclay

Contact :

François PARMENTIER

Patrice ROCHE

Starting date : 01-10-2018

Contact :

François PARMENTIER

CEA - DRF/IRAMIS/SPEC/GNE

+33169087311

Thesis supervisor :

Patrice ROCHE

CEA - DRF/IRAMIS/SPEC/GNE

0169087216

Laboratory link : http://nanoelectronics.wikidot.com/research

The goal of this project is to explore quantum transport of heat in new states of matter arising in ultra-clean graphene in high magnetic fields, using ultra-sensitive electronic noise measurements.



The ability to obtain ultra-clean graphene (a two-dimensional crystal made of Carbon atoms in a honeycomb lattice) samples has recently allowed the observation of new phases of condensed matter in graphene under high magnetic fields. In particular, new states of the quantum Hall effect were observed at low charge carrier density [1], where interactions and electronic correlations can either make graphene completely electrically insulating, or give rise to the quantum spin Hall effect. In the latter, the bulk of the two-dimensional crystal is insulating, while electronic current is only carried along the edges of the crystal, with opposite spins propagating in opposite directions. The exact nature of those various states is still not fully understood, as one cannot probe the properties of the insulating regions by usual electron transport measurements.



We propose a new approach to probe those phases, based on the measurement of quantum heat flow carried by chargeless excitations such as spin waves, at very low temperature. Our method will consist in connecting the graphene crystal to small metallic electrodes which will be used as heat reservoirs. The temperature of each reservoir will be inferred by ultra-sensitive noise measurements [2], allowing us to extract the heat flow.



The first step of this project will consist in fabricating the samples made of graphene encapsulated in hexagonal boron nitride [3]. This technique, which we have recently developed in our lab, allows to obtain large-area, ultra-clean graphene flakes. In parallel, an experimental platform for low-temperature, high magnetic field, ultra-high sensitivity noise measurements will be set up.



[1] Young et al., Nature 505, 528-532 (2014).

[2] Jezouin, Parmentier et al., Science 342, 601 (2013).

[3] Wang et al., Science 342, 614 (2013).

Dissipation, cascades and singularities in turbulence

SL-DRF-18-0272

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

Personal web page : http://iramis.cea.fr/Pisp/berengere.dubrulle/index.html

Laboratory link : 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.

New electronic states in single crystals and thin films of iridates

SL-DRF-18-0419

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 : 01-10-2018

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

Personal web page : http://iramis.cea.fr/spec/Pisp/jean-baptiste.moussy/

Laboratory link : 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 (insulator with metallic surface states). 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.

Highly spin-polarized electron transport in organic molecule-based magnetic junctions

SL-DRF-18-0443

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 :

Alexander SMOGUNOV

Starting date : 01-05-2018

Contact :

Alexander SMOGUNOV

CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Thesis supervisor :

Alexander SMOGUNOV

CEA - DRF/IRAMIS/SPEC/GMT

0169083032

Personal web page : http://iramis.cea.fr/Pisp/alexander.smogunov/

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

We propose to study theoretically spin-polarized electron transport in tunnel junctions made of organic molecules connecting two ferromagnetic electrodes – the subject of great interest in the field of organic/molecular spintronics [1]. The particular stress will be made on the possibility to optimize and to control the degree of spin-polarization of electric current and the magnetoresistance of a junction – very important properties in spintronics – by a clever choice of molecules themselves or by some external stimuli such as a temperature (via interaction of electrons with molecule vibrations), an electric field (a gate), or a mechanical strain exerted on the molecule by electrodes. We will especially exploit a symmetry aspect of electronic orbitals of a molecule – the idea which we have recently proposed [2] – which can allow to spin-filter the electric current in the most efficient way. The combination of ab initio DFT (Density Functional Theory) electronic structure methods, as implemented in the Quantum ESPRESSO (QE) package [3], with model electron transport calculations, based on the Keldysh formalism, will be used during the project. Various new functionalities and features such as, for example, an electron-phonon coupling at the molecule or a thermal transport, will be implemented in both QE and electron transport codes.



[1] A. R. Rocha et al., Towards molecular spintronics, Nature Mater. 4, 335(2005); S. Sanvito,

Molecular spintronics, Chem. Soc. Rev. 40, 3336 (2011); V. Alek Dediu et al., Spin routes in

organic semiconductors, Nature Mater. 8, 707 (2009);

[2] A. Smogunov and Y. J. Dappe, Symmetry-Derived Half-Metallicity in Atomic and Molecular

Junctions, Nano Lett. 15, 3552 (2015);

[3] P. Giannozzi et al., QUANTUM ESPRESSO: a modular and open-source software project for

quantum simulations of materials, Phys.: Condens. Matter 21, 395502 (2009).

In operando study of ferrite - perovskite multiferroic encapsulated microstructures

SL-DRF-18-0351

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 : 01-10-2018

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

Personal web page : http://iramis.cea.fr/Pisp/137/antoine.barbier.html

Laboratory link : 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 multiferroïc 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 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 behavior of these inclusions under functioning conditions will be examined using the most advanced synchrotron radiations techniques and in particular spectro-microscopy, 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 and magnetometry, as well as in the above mentioned state of the art synchrotron radiation techniques.

Epsilon-Near-Zero modes in metamaterials for optoelectronics

SL-DRF-18-0399

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 :

Simon VASSANT

Starting date : 01-10-2018

Contact :

Simon VASSANT

CEA - DRF/IRAMIS/SPEC/LEPO

+33 169 089 597

Thesis supervisor :

Simon VASSANT

CEA - DRF/IRAMIS/SPEC/LEPO

+33 169 089 597

Personal web page : http://iramis.cea.fr/Pisp/simon.vassant/index.php

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

Our team has already demonstrated theoretically and experimentally the interest of specific electromagnetic modes (epsilon-near-zero modes) for optoelectronics. These modes allow the confinement of light in a layer of sub-wavelength thickness (less than the penetration depth of the light), and thus maximize the interaction between photon and the matter.



The subject of PhD deals with the design, realization and characterization of artificial materials (metamaterials) to realize and control these electromagnetic modes.



Two approaches will be considered:

- The first is based on quantum cascade detector concepts, in partnership with C2N, ONERA, the Institut d'Optique and the 3-5 Lab (Thalès) as part of an ANR project funded from 2018 to 2022.

- The second, more exploratory, proposes to use supra-molecular assemblies on graphene. This technique is at the heart of the laboratory's expertise.



The doctoral student will have to model the structures to be created (using available numerical codes), then will have to manufacture and characterize the samples made. Part of the manufacturing will be done in clean room.

Ultra low field Magnetic Resonance Imaging

SL-DRF-18-0386

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 :

Claude FERMON

Starting date : 01-10-2018

Contact :

Claude FERMON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 01

Thesis supervisor :

Claude FERMON

CEA - DRF/IRAMIS/SPEC/LNO

01 69 08 94 01

We have developed magnetic hybrid sensors based on the association of a superconducting loop to a micron size giant magnetoresistive sensor. These sensors will allow exploring a new field: Nuclear Magnetic Resonance and Magnetic Resonance Imaging at very low fields (of the order of a milliTesla).



A full head very low field MRI prototype has been built and has demonstrated the approach. The goal of the PhD will be firstly to participate to the installation of the system at Neurospin and implement fast acquisition schemes. In addition, a work on the next generation of magnetic sensors based on tunnel magnetic junctions will be performed to improve the signal to noise of the system.

ToughGlasses: Researching tomorrow’s glasses today

SL-DRF-18-0227

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

Service de Physique de l'Etat Condensé (SPEC)

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

Saclay

Contact :

Cindy ROUNTREE

Starting date : 01-10-2018

Contact :

Cindy ROUNTREE

CEA - DRF/IRAMIS/SPEC/SPHYNX

+33 1 69 08 26 55

Thesis supervisor :

Cindy ROUNTREE

CEA - DRF/IRAMIS/SPEC/SPHYNX

+33 1 69 08 26 55

Personal web page : http://iramis.cea.fr/Pisp/cindy.rountree/

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

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

The 3 years of this PhD subject are today funded by an ANR project. Decision by the laboratory over a candidature will be given early (beginning of spring 2018).



ToughGlasses is a fundamental research project motivated by the need to improve and assess glasses mechanical durability over the long term. Glasses are integral parts our daily lives (buildings, cars, dishes…) along with being integral parts of heat resistant technologies, protection panels (smart phones, plasma screens…), low-carbon energies (protection for solar panels) and satellites in outer space to name a few. These systems and others undergo a variety of damage (consumer use, sand storms, external irradiations, high temperatures…) which can lead to premature failure and/or alterations of the physical and mechanical properties. Frequently, post-mortem failure studies reveal material flaws which were propagating via Stress Corrosion Cracking (SCC). A recent question arriving in the field has been: Can the Amorphous Phase Separation (APS) of SiO2-B2O3-Na2O (SBN) glasses provide the necessary structure to enhanced SCC behavior? ToughGlasses aim is to fill this gap and to unravel the secret behind enhanced SCC behavior.



The Ph.D. candidate will have the opportunity to study the physical, mechanical and stress-corrosion cracking properties of APS glasses. The primary objective of this study will be to observe stress corrosion crack propagation in situ and the analysis of fracture surfaces in several pristine and APS glasses. Hence, providing information on environmental limit of stress corrosion cracking and understanding of how the crack growth occurs in APS glasses. This method was previously used in our group to study the process zone size versus the crack front velocity in pure silica (SiO2) and several SBN samples. Repeating this study for SBN APS glasses compositions will aid in the understanding of how the physical structure of glasses alters the mechanical properties. In conjunction with the primary objective, the candidate will have the occasion to characterize the elastic properties of the samples and their structures (Raman, NMR spectroscopy, X-ray absorption …) with various collaborators including collaborators in CEA, DEN and University of Rennes. This will allow for a comparison of the fracture behavior of glasses with other macroscopic and microscopic properties.



Logistically, the candidate will be co-advised by C. L. Rountree at CEA and F. Célarié at Université de Rennes 1. Glass formation and preliminary tests will occur at Université de Rennes 1 and stress corrosion cracking tests along with other tests will be carried out at CEA. In conclusion, the theme of this project is the comprehension of the source of the changes in the macroscopic property, and in particular how to control the stress corrosion cracking properties by varying the structure of glasses through Amorphous Phase Separation.



Some Relevant Publications:

1) “SiO2-Na2O-B2O3 density: A comparison of experiments, simulations, and theory.”

M. Barlet, A. Kerrache, J-M Delaye, and C. L. Rountree Journal of Non-Crystalline Solids. 382, 32, (2013)

2) "Hardness and Toughness of Sodium Borosilicate Glasses via Vicker's indentations”

M. Barlet, J-M. Delaye, T. Charpentier, M. Gennisson, D. Bonamy, T. Rouxel, C.L. Rountree

Journal of Non-Crystalline Solids. 417–418:66-69 (June 2015).

DOI:10.1016/j.jnoncrysol.2015.02.005

3) “Role of evaporation rate on the particle organization and crack patterns obtained by drying a colloidal layer”

K. Piroird, V. Lazarus, G. Gauthier, A. Lesaine, D. Bonamy and C. L. Rountree

Europhysics Letters, 113:38002 (February 2016).

4) “From network depolymerization to stress corrosion cracking in sodium-borosilicate glasses: Effect of the chemical composition.”

M. Barlet, J.-M. Delaye, B. Boizot, D. Bonamy, R. Caraballo, S. Peuget and C. L. Rountree

Journal of Non-Crystalline Solids. 450:174-184 (15 October 2016).

Generation of hot electrons of plasmonic origin: Physics and applications

SL-DRF-18-0292

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 :

Ludovic DOUILLARD

Starting date : 01-10-2018

Contact :

Ludovic DOUILLARD

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 36 26

Thesis supervisor :

Ludovic DOUILLARD

CEA - DRF/IRAMIS/SPEC/LEPO

01 69 08 36 26

Personal web page : http://iramis.cea.fr/Pisp/ludovic.douillard/

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

Physics and applications of hot electrons of plasmonic origin



At small scale, the interaction of light with a metal object results in the occurrence of remarkable resonances within the absorption spectrum, the plasmon resonances. These resonances correspond to collective oscillations of the charge carriers [Mie 1908] and constitute a research domain in itself known as Plasmonic. Beyond its interest in the manipulation of the near optical field, a metal object at plasmonic resonance is a source of hot electrons whose electronic properties can be used to achieve non classical chemistry reactions at the local scale.



This work aims to study the fundamental physics of the emission of hot electrons by a nanometric metal object in connection with applications, particularly medical ones such as the anticancer photodynamic therapies. It is a work of experimental character in close collaboration to a relevant partnership of physicists, chemists, biologists and oncologists from different Institutions (CEA, CentraleSupélec, Saint-Louis Hospital). It will benefit from the experience acquired by the CEA IRAMIS SPEC group in LEEM / PEEM (Low Energy Electron / PhotoEmission Electron Microscopy) microscopies, the principle of which is based directly on the acquisition of the distribution of the photoelectrons emitted in response to a plasmon resonance decay [Douillard 2012, 2011] and is therefore a unique technique of choice for this study.



The objectives are to answer fundamental questions related to the emission of hot electrons by a metal particle under ultrafast multiphoton optical excitation. In particular, this involves determining the emission dynamics of the charge carriers (pump probe experiment) and their physical distributions : spatial mapping of the emission hot spots at the nano-object scale and energy mapping through the determination of the kinetic energy spectra. The ultimate goal takes place in the context of a project devoted to medical oncology and more specifically on the optimization of anticancer therapies under development, namely the photothermal and photodynamic therapies.



Keywords: hot electrons, plasmon, laser, PEEM, LEEM



[Mie 1908] G. Mie, Ann. Phys. (Leipzig) 25 (1908) 377

[Douillard 2012, 11] C. Awada, et al. J. of Phys. Chem. C 16 (2012) 14591 DOI 10.1021/jp303475c, L. Douillard, F. Charra. J. of Phys. D: Applied Physics 44 (2011) 464002 DOI:10.1088/0022-3727/44/46/464002, C. Hrelescu, et al. Nano Lett. 11 (2011) 402–407 DOI: 10.1021/nl103007m



Laboratoire d’accueil CEA IRAMIS SPEC UMR 3680

Correspondant CEA chargé du suivi de la thèse ludovic.douillard@cea.fr

Ecole doctorale Ondes et Matière, Univ. Paris Saclay.

Tunable multicomponent supramolecular magnetic self-assembly for spintronics

SL-DRF-18-0337

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 : 01-10-2018

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

Personal web page : http://iramis.cea.fr/Pisp/fabien.silly/index.html

Laboratory link : 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.

Superparamagnetic transitions in 3D superlattices of magnetic nanocrystals

SL-DRF-18-0451

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

Service de Physique de l'Etat Condensé (SPEC)

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

Saclay

Contact :

caroline RAEPSAET

Sawako NAKAMAE

Starting date : 01-10-2018

Contact :

caroline RAEPSAET

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169082423

Thesis supervisor :

Sawako NAKAMAE

CEA - DRF/IRAMIS/SPEC/SPHYNX

0169087538

Laboratory link : https://iramis.cea.fr/spec/SPHYNX

Interactions between magnetic nanocrystals give rise to a large variety of magnetic behaviors, grouped together in a new field of physics called "supermagnetism." In this PhD project, we propose an experimental study of supermagnetic transitions; i.e., superspin glass (SSG) and dipolar superferromagnetism (SFM), in supracrystals (SC) of cobalt nanoparticles (NP) controlled by structural constraints.



We are working with 3D supracrystals, which are artificial solids which building block is not the atom but the nanoparticle. As in atomic solids, nanocrystals are organized in a specific structure such as face centered cubic (cfc) structure. The dipolar moments of nanocrystals are thus found on regular supra-lattice sites, and interact with one another through dipolar interactions. The geometric simplicity of these supracrystals offers a “real” and “simple” system that can be modelled numerically and theoretically. Supracrystal samples are prepared at the MONARIS UPMC/CNRS laboratory, with controlled NP and SC crystallinity and morphology conditions.



The proposed study concerns the experimental study of the evolution of the magnetic states of supracrystals of Co nanoparticles. Two measurements methods will be used, globally, by SQUID (Superconducting Quantum Interference Device) magnetometry and microscopically, using miniature Hall-probes. With the latter technique, we hope to detect the ferromagnetic transition in a single domain supracrystal, a decisive experimental proof of the existence dipolar SFM.



The main issue of this work concerns fundamental physico-chemistry, by evidencing the dipolar SFM in 3D superlattices. Predicted by theoretical studies, it hasn’t been observed yet. This experimental study will require a strong collaboration with the theoreticians, for interpreting the experimental results as well as validating the modelization. SFM supracrystals will find applications in the medical field, for data storage…



The competences required for the proposed study will include NP magnetism, magnetic measurements techniques (ultra-sensitive magnetometry integrating very low noise measurements), cryogenic technics, statistical analysis and experimental results interpretation. Motivated candidates will have the possibility to participate to the NP and SC synthesis, and to their structural characterization (SAXS, MET, MEB…).

Magnetic properties of differently-shaped metal nanocrystals

SL-DRF-18-0336

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

Personal web page : http://iramis.cea.fr/Pisp/fabien.silly/index.html

Laboratory link : 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.

Theoretical investigation of the magnetic anistropy of hybrid systems for molecular spintronics

SL-DRF-18-0045

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 : 01-12-2017

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

Personal web page : http://iramis.cea.fr/Pisp/cyrille.barreteau/

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

Nanomagnetism is an active field at the frontier of various domains. It consists in the study (and use) of the magnetism of nanometer sized systems. Magnetic properties of nano-objects generally strongly differ from their bulk counterpart. A major issue is to control/manipulate their magnetic properties. One of the fundamental properties of magnetic materials is their magnetic anisotropy which is characterized by their easy axis but also anisotropic magnetoresistance (AMR). It has been recently demonstrated that the interaction between a magnetic thin film and adsorbed molecules can greatly modify the anisotropy of the film due to hybridization between the molecule and the surface atoms of the substrate. Recent experiments have also shown that large AMR can be achieved in “simple” systems such as nano-conctrictions of nickel connected via a benzene molecule.

In this internship we propose to study via electronic structure methods (ab-initio and/or tight-binding) the magnetic anisotropy of few simple systems. We will first consider cobalt and iron thin films in interaction with simple molecules. More complex systems will be further investigated. The final goal is to find systems molecule/substrate with optimal properties in view of possible applications.

Water photo-electrolysis assisted by an internal potential

SL-DRF-18-0353

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

Personal web page : http://iramis.cea.fr/Pisp/helene.magnan/

Laboratory link : 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.

 

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