11 research outputs found
Transport hélical et interférométrie de Fabry-Pérot en régime d'effet Hall quantique dans le graphÚne
In the quantum Hall regime, the Coulomb interactions lead to the emergence of various highly correlated electronic phases exhibiting striking statistical and topological properties. The recent development of high mobility graphene van der Waals heterostructures has opened new opportunities for the study of these phases and the interplay between quantum Hall physics and other condensed matter phenomena. In this PhD thesis, we have developed new types of nanostructures that could enable to probe and to exploit some of the unique properties of the correlated quantum Hall phases developing in graphene.Using high-k dielectric SrTiO3 substrates, we have fabricated graphene devices where a phase exhibiting a helical edge transport develops at charge neutrality and at low magnetic fields. We show that this helical quantum Hall phase stems from the screening of the long-range Coulomb interaction by the substrate. We demonstrate that this helical edge transport survives over micron long distances and is robust up to a temperature of 110 K, thus providing a promising platform to investigate topological superconductivity.We also have successfully fabricated encapsulated graphene heterostructures equipped with quantum point contacts in series that operate as quantum Hall Fabry-PĂ©rot interferometers. We demonstrate that these devices display gate-tunable oscillations that arise from the Aharonov-Bohm effect in remarkable agreement with the theory. We investigate the quantum coherence of electron transport in these interferometers and the possibility to operate a coherent double Fabry-PĂ©rot interferometer. We show that our graphene Fabry-PĂ©rot interferometers also exhibit an intriguing transport regime where Aharanov-Bohm oscillations have a halved periodicity. We finally investigate the possibility to make interference in the fractional quantum Hall regime and we unveil the existence of phase jumps in Aharonov-Bohm oscillations, that are reminiscent of the signatures of anyonic quasiparticles, in a configuration where such features should not be observed. Our work demonstrates that graphene devices offer a new platform to investigate the physics of quantum Hall Fabry-PĂ©rot interferometers and open new paths towards the probing of anyon physics emerging the fractional quantum Hall regime.En rĂ©gime dâeffet Hall quantique, les interactions coulombiennes entrainent la formation de nombreuses phases Ă©lectroniques hautement corrĂ©lĂ©es arborant des propriĂ©tĂ©s topologiques et des statistiques hors du commun. Le rĂ©cent dĂ©veloppement des hĂ©tĂ©rostructures de graphĂšne de haute mobilitĂ© a offert de nouvelles opportunitĂ©s pour lâĂ©tude de ces phases ainsi que pour explorer le couplage entre lâeffet Hall quantique et dâautres phĂ©nomĂšnes de la matiĂšre condensĂ©e. Dans ce travail de thĂšse, nous avons dĂ©veloppĂ© de nouvelles nanostructures qui permettent de sonder et dâexploiter certaines des propriĂ©tĂ©s uniques des phases corrĂ©lĂ©es se dĂ©veloppant en rĂ©gime dâeffet Hall quantique dans le graphĂšne.En utilisant des substrats de SrTiO3 Ă haute constante diĂ©lectrique, nous avons fabriquĂ© des dispositifs dans lesquels un transport hĂ©lical apparait au point de neutralitĂ© et Ă bas champs magnĂ©tiques. Nous montrons que cette phase hĂ©licale se dĂ©veloppe grĂące Ă lâĂ©crantage par le substrat de lâinteraction coulombienne longue portĂ©e. Dans cette phase le transport reste hĂ©lical sur des distances micromĂ©triques et jusquâĂ 110 K ce qui en fait un systĂšme de choix pour lâĂ©tude de la superconductivitĂ© topologique.La seconde partie de cette thĂšse a consistĂ© en la rĂ©alisation dâinterfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique Ă base dâhĂ©terostructures de graphĂšne encapsulĂ© Ă©quipĂ©es de contacts ponctuels quantiques. Nous dĂ©montrons lâexistence, dans ces dispositifs, dâoscillations Aharanov-Bohm contrĂŽlables par des grilles Ă©lectrostatiques, en parfait accord avec les prĂ©dictions thĂ©oriques. Nous Ă©tudions la cohĂ©rence du transport Ă©lectronique dans ces interfĂ©romĂštres ainsi que la possibilitĂ© de mettre en place un double interfĂ©romĂštre dans lequel le transport reste cohĂ©rent. Par ailleurs, nous montrons quâil existe, dans ces interfĂ©romĂštres, un rĂ©gime de transport particulier dans lequel les oscillations Aharanov-Bohm ont une pĂ©riodicitĂ© rĂ©duite de moitiĂ©. Nous Ă©tudions, enfin, la possibilitĂ© de rĂ©aliser des expĂ©riences dâinterfĂ©romĂ©trie en rĂ©gime dâeffet Hall quantique fractionnaire et nous mettons en Ă©vidence lâexistence de sauts de phases dans les oscillations Aharonov-Bohm ne pouvant pas ĂȘtre interprĂ©tĂ©s comme des signatures de statistiques anyoniques. Notre travail montre que les dispositifs Ă base de graphĂšne offrent de nouvelles opportunitĂ©s pour lâĂ©tude des interfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique et ouvrent de nouvelles perspectives pour explorer la physique des anyons Ă©mergeant en rĂ©gime fractionnaire
The Micro-ARES instrument on ExoMars 2016
Divers phĂ©nomĂšnes d'ionisation et d'Ă©lectrification atmosphĂ©riques existent dans la plupart des environnements planĂ©taires connus et les conditions dans la basse atmosphĂšre de Mars sont propices Ă l'Ă©tablissement de champs Ă©lectriques potentiellement trĂšs Ă©levĂ©s. La raison d'ĂȘtre de Micro-ARES, le capteur de champ Ă©lectrique et de conductivitĂ© de la suite mĂ©tĂ©o DREAMS, seule charge utile scientifiques de l'atterrisseur Schiaparelli de la mission ExoMars 2016, Ă©tait de dĂ©fricher cette Ă©lectricitĂ© atmosphĂ©rique martienne. LâĂ©tude de lâactivitĂ© Ă©lectrique ainsi que de la gĂ©nĂ©ration de ces champs Ă©lectriques dans les tempĂȘtes de poussiĂšres martiennes permettrait de faire la lumiĂšre sur divers phĂ©nomĂšnes physiques : La dynamique des poussiĂšres Ă lâĂ©chelle locale et planĂ©taire, Ă©lĂ©ment clĂ© du climat martien, la peu comprise ionosphĂšre martienne ou encore la chimie atmosphĂ©rique et plus prĂ©cisĂ©ment lâĂ©nigme du mĂ©thane martien.La thĂšse prĂ©sentĂ©e ici dĂ©taille le dĂ©veloppement matĂ©riel et logiciel de Micro-ARES, les tests subits par lâinstrument aussi bien en chambre que sur le terrain, ainsi que le traitement des donnĂ©es et la physique qui sous-tend le fonctionnement de lâinstrument. Puisque de futures mission embarqueront trĂšs probablement ce type de capteur polyvalent, lĂ©ger et consommant peu, lâaccent a Ă©tĂ© mis sur la modĂ©lisation de lâinteraction entre lâĂ©lectrode et lâatmosphĂšre. Ce travail thĂ©orique dĂ©passe le cadre de Micro-ARES sur ExoMars 2016 et est une Ă©tape nĂ©cessaire dans la comprĂ©hension et le traitement des biais induits aussi bien par lâenvironnement de lâinstrument, son design simplifiĂ© et les comportements inattendus de lâatmosphĂšre martienne.Atmosphere ionization and electrification mechanisms of various sorts are known to exist in most of the planetary environments. It appears that the lower atmosphere and surface of Mars combine a number of favorable conditions for the development of intense atmospheric electric fields. Unveiling the Martian atmospheric electricity was the original goal of Micro-ARES, the electric-field and conductivity sensor of the DREAMS meteorological suite, the only scientific payload that equipped the Schiaparelli module from the ExoMars 2016 mission.The study of the electrical activity and electric field generation in Martian dust events might bring new capital knowledge on a wide range of phenomena: The local and planetary scale dust dynamics, a major component of the Martian climate, the partially understood Martian ionosphere, atmospheric chemistry and more precisely the production and destruction of the Martian methane, a still unresolved mystery.The following thesis details the hardware and software development of Micro-ARES, its testing phases, both in laboratory and on the field, and the data processing and physical processes underlying the instrumentâs operation. Since future missions may carry again these kind of polyvalent, lightweight and energy-efficient sensor, emphasis was put on the modeling of the instrument's electrical coupling with the atmosphere. This theoretical work exceeds the frame of Micro-ARES in ExoMars 2016 and is necessary in order to understand and accurately compensate the biases induced by the instrument's surroundings, its simplified design and the unexpected electrical behavior of the Martian atmosphere
Helical edge transport and Fabry-PĂ©rot interferometry in graphene quantum Hall effect
En rĂ©gime dâeffet Hall quantique, les interactions coulombiennes entrainent la formation de nombreuses phases Ă©lectroniques hautement corrĂ©lĂ©es arborant des propriĂ©tĂ©s topologiques et des statistiques hors du commun. Le rĂ©cent dĂ©veloppement des hĂ©tĂ©rostructures de graphĂšne de haute mobilitĂ© a offert de nouvelles opportunitĂ©s pour lâĂ©tude de ces phases ainsi que pour explorer le couplage entre lâeffet Hall quantique et dâautres phĂ©nomĂšnes de la matiĂšre condensĂ©e. Dans ce travail de thĂšse, nous avons dĂ©veloppĂ© de nouvelles nanostructures qui permettent de sonder et dâexploiter certaines des propriĂ©tĂ©s uniques des phases corrĂ©lĂ©es se dĂ©veloppant en rĂ©gime dâeffet Hall quantique dans le graphĂšne.En utilisant des substrats de SrTiO3 Ă haute constante diĂ©lectrique, nous avons fabriquĂ© des dispositifs dans lesquels un transport hĂ©lical apparait au point de neutralitĂ© et Ă bas champs magnĂ©tiques. Nous montrons que cette phase hĂ©licale se dĂ©veloppe grĂące Ă lâĂ©crantage par le substrat de lâinteraction coulombienne longue portĂ©e. Dans cette phase le transport reste hĂ©lical sur des distances micromĂ©triques et jusquâĂ 110 K ce qui en fait un systĂšme de choix pour lâĂ©tude de la superconductivitĂ© topologique.La seconde partie de cette thĂšse a consistĂ© en la rĂ©alisation dâinterfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique Ă base dâhĂ©terostructures de graphĂšne encapsulĂ© Ă©quipĂ©es de contacts ponctuels quantiques. Nous dĂ©montrons lâexistence, dans ces dispositifs, dâoscillations Aharanov-Bohm contrĂŽlables par des grilles Ă©lectrostatiques, en parfait accord avec les prĂ©dictions thĂ©oriques. Nous Ă©tudions la cohĂ©rence du transport Ă©lectronique dans ces interfĂ©romĂštres ainsi que la possibilitĂ© de mettre en place un double interfĂ©romĂštre dans lequel le transport reste cohĂ©rent. Par ailleurs, nous montrons quâil existe, dans ces interfĂ©romĂštres, un rĂ©gime de transport particulier dans lequel les oscillations Aharanov-Bohm ont une pĂ©riodicitĂ© rĂ©duite de moitiĂ©. Nous Ă©tudions, enfin, la possibilitĂ© de rĂ©aliser des expĂ©riences dâinterfĂ©romĂ©trie en rĂ©gime dâeffet Hall quantique fractionnaire et nous mettons en Ă©vidence lâexistence de sauts de phases dans les oscillations Aharonov-Bohm ne pouvant pas ĂȘtre interprĂ©tĂ©s comme des signatures de statistiques anyoniques. Notre travail montre que les dispositifs Ă base de graphĂšne offrent de nouvelles opportunitĂ©s pour lâĂ©tude des interfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique et ouvrent de nouvelles perspectives pour explorer la physique des anyons Ă©mergeant en rĂ©gime fractionnaire.In the quantum Hall regime, the Coulomb interactions lead to the emergence of various highly correlated electronic phases exhibiting striking statistical and topological properties. The recent development of high mobility graphene van der Waals heterostructures has opened new opportunities for the study of these phases and the interplay between quantum Hall physics and other condensed matter phenomena. In this PhD thesis, we have developed new types of nanostructures that could enable to probe and to exploit some of the unique properties of the correlated quantum Hall phases developing in graphene.Using high-k dielectric SrTiO3 substrates, we have fabricated graphene devices where a phase exhibiting a helical edge transport develops at charge neutrality and at low magnetic fields. We show that this helical quantum Hall phase stems from the screening of the long-range Coulomb interaction by the substrate. We demonstrate that this helical edge transport survives over micron long distances and is robust up to a temperature of 110 K, thus providing a promising platform to investigate topological superconductivity.We also have successfully fabricated encapsulated graphene heterostructures equipped with quantum point contacts in series that operate as quantum Hall Fabry-PĂ©rot interferometers. We demonstrate that these devices display gate-tunable oscillations that arise from the Aharonov-Bohm effect in remarkable agreement with the theory. We investigate the quantum coherence of electron transport in these interferometers and the possibility to operate a coherent double Fabry-PĂ©rot interferometer. We show that our graphene Fabry-PĂ©rot interferometers also exhibit an intriguing transport regime where Aharanov-Bohm oscillations have a halved periodicity. We finally investigate the possibility to make interference in the fractional quantum Hall regime and we unveil the existence of phase jumps in Aharonov-Bohm oscillations, that are reminiscent of the signatures of anyonic quasiparticles, in a configuration where such features should not be observed. Our work demonstrates that graphene devices offer a new platform to investigate the physics of quantum Hall Fabry-PĂ©rot interferometers and open new paths towards the probing of anyon physics emerging the fractional quantum Hall regime
Transport hélical et interférométrie de Fabry-Pérot en régime d'effet Hall quantique dans le graphÚne
In the quantum Hall regime, the Coulomb interactions lead to the emergence of various highly correlated electronic phases exhibiting striking statistical and topological properties. The recent development of high mobility graphene van der Waals heterostructures has opened new opportunities for the study of these phases and the interplay between quantum Hall physics and other condensed matter phenomena. In this PhD thesis, we have developed new types of nanostructures that could enable to probe and to exploit some of the unique properties of the correlated quantum Hall phases developing in graphene.Using high-k dielectric SrTiO3 substrates, we have fabricated graphene devices where a phase exhibiting a helical edge transport develops at charge neutrality and at low magnetic fields. We show that this helical quantum Hall phase stems from the screening of the long-range Coulomb interaction by the substrate. We demonstrate that this helical edge transport survives over micron long distances and is robust up to a temperature of 110 K, thus providing a promising platform to investigate topological superconductivity.We also have successfully fabricated encapsulated graphene heterostructures equipped with quantum point contacts in series that operate as quantum Hall Fabry-PĂ©rot interferometers. We demonstrate that these devices display gate-tunable oscillations that arise from the Aharonov-Bohm effect in remarkable agreement with the theory. We investigate the quantum coherence of electron transport in these interferometers and the possibility to operate a coherent double Fabry-PĂ©rot interferometer. We show that our graphene Fabry-PĂ©rot interferometers also exhibit an intriguing transport regime where Aharanov-Bohm oscillations have a halved periodicity. We finally investigate the possibility to make interference in the fractional quantum Hall regime and we unveil the existence of phase jumps in Aharonov-Bohm oscillations, that are reminiscent of the signatures of anyonic quasiparticles, in a configuration where such features should not be observed. Our work demonstrates that graphene devices offer a new platform to investigate the physics of quantum Hall Fabry-PĂ©rot interferometers and open new paths towards the probing of anyon physics emerging the fractional quantum Hall regime.En rĂ©gime dâeffet Hall quantique, les interactions coulombiennes entrainent la formation de nombreuses phases Ă©lectroniques hautement corrĂ©lĂ©es arborant des propriĂ©tĂ©s topologiques et des statistiques hors du commun. Le rĂ©cent dĂ©veloppement des hĂ©tĂ©rostructures de graphĂšne de haute mobilitĂ© a offert de nouvelles opportunitĂ©s pour lâĂ©tude de ces phases ainsi que pour explorer le couplage entre lâeffet Hall quantique et dâautres phĂ©nomĂšnes de la matiĂšre condensĂ©e. Dans ce travail de thĂšse, nous avons dĂ©veloppĂ© de nouvelles nanostructures qui permettent de sonder et dâexploiter certaines des propriĂ©tĂ©s uniques des phases corrĂ©lĂ©es se dĂ©veloppant en rĂ©gime dâeffet Hall quantique dans le graphĂšne.En utilisant des substrats de SrTiO3 Ă haute constante diĂ©lectrique, nous avons fabriquĂ© des dispositifs dans lesquels un transport hĂ©lical apparait au point de neutralitĂ© et Ă bas champs magnĂ©tiques. Nous montrons que cette phase hĂ©licale se dĂ©veloppe grĂące Ă lâĂ©crantage par le substrat de lâinteraction coulombienne longue portĂ©e. Dans cette phase le transport reste hĂ©lical sur des distances micromĂ©triques et jusquâĂ 110 K ce qui en fait un systĂšme de choix pour lâĂ©tude de la superconductivitĂ© topologique.La seconde partie de cette thĂšse a consistĂ© en la rĂ©alisation dâinterfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique Ă base dâhĂ©terostructures de graphĂšne encapsulĂ© Ă©quipĂ©es de contacts ponctuels quantiques. Nous dĂ©montrons lâexistence, dans ces dispositifs, dâoscillations Aharanov-Bohm contrĂŽlables par des grilles Ă©lectrostatiques, en parfait accord avec les prĂ©dictions thĂ©oriques. Nous Ă©tudions la cohĂ©rence du transport Ă©lectronique dans ces interfĂ©romĂštres ainsi que la possibilitĂ© de mettre en place un double interfĂ©romĂštre dans lequel le transport reste cohĂ©rent. Par ailleurs, nous montrons quâil existe, dans ces interfĂ©romĂštres, un rĂ©gime de transport particulier dans lequel les oscillations Aharanov-Bohm ont une pĂ©riodicitĂ© rĂ©duite de moitiĂ©. Nous Ă©tudions, enfin, la possibilitĂ© de rĂ©aliser des expĂ©riences dâinterfĂ©romĂ©trie en rĂ©gime dâeffet Hall quantique fractionnaire et nous mettons en Ă©vidence lâexistence de sauts de phases dans les oscillations Aharonov-Bohm ne pouvant pas ĂȘtre interprĂ©tĂ©s comme des signatures de statistiques anyoniques. Notre travail montre que les dispositifs Ă base de graphĂšne offrent de nouvelles opportunitĂ©s pour lâĂ©tude des interfĂ©romĂštres de Fabry-PĂ©rot en rĂ©gime dâeffet Hall quantique et ouvrent de nouvelles perspectives pour explorer la physique des anyons Ă©mergeant en rĂ©gime fractionnaire
Discovery of Novel <i>N</i>-Phenylphenoxyacetamide Derivatives as EthR Inhibitors and Ethionamide Boosters by Combining High-Throughput Screening and Synthesis
In this paper, we describe the screening of a 14640-compound
library
using a novel whole mycobacteria phenotypic assay to discover inhibitors
of EthR, a transcriptional repressor implicated in the innate resistance
of Mycobacterium tuberculosis to the
second-line antituberculosis drug ethionamide. From this screening
a new chemical family of EthR inhibitors bearing an <i>N</i>-phenylphenoxyacetamide motif was identified. The X-ray structure
of the most potent compound crystallized with EthR inspired the synthesis
of a 960-member focused library. These compounds were tested in vitro
using a rapid thermal shift assay on EthR to accelerate the optimization.
The best compounds were synthesized on a larger scale and confirmed
as potent ethionamide boosters on M. tuberculosis-infected macrophages. Finally, the cocrystallization of the best
optimized analogue with EthR revealed an unexpected reorientation
of the ligand in the binding pocket
Ethionamide Boosters. 2. Combining Bioisosteric Replacement and Structure-Based Drug Design To Solve Pharmacokinetic Issues in a Series of Potent 1,2,4-Oxadiazole EthR Inhibitors
Mycobacterial transcriptional repressor EthR controls
the expression
of EthA, the bacterial monooxygenase activating ethionamide, and is
thus largely responsible for the low sensitivity of the human pathogen <i>Mycobacterium tuberculosis</i> to this antibiotic. We recently
reported structureâactivity relationships of a series of 1,2,4-oxadiazole
EthR inhibitors leading to the discovery of potent ethionamide boosters.
Despite high metabolic stability, pharmacokinetic evaluation revealed
poor mice exposure; therefore, a second phase of optimization was
required. Herein a structureâproperty relationship study is
reported according to the replacement of the two aromatic heterocycles:
2-thienyl and 1,2,4-oxadiazolyl moieties. This work was done using
a combination of structure-based drug design and in vitro/ex vivo evaluations of ethionamide boosters on the targeted protein EthR
and on the human pathogen <i>Mycobacterium tuberculosis</i>. Thanks to this process, we identified compound <b>42</b> (BDM41906), which displays improved efficacy in addition to high
exposure to mice after oral administration