In the last decade, a large number of studies have been devoted to the peculiarities of correlated physics found in the quasi-two-dimensional square lattice iridium oxides. It was shown that this 5d family of transition metal oxides has strong structural and electronic similarities to the famous 3d family of copper oxides. Moreover, a delicate interplay of on-site spin-orbit coupling, Coulomb repulsion and crystalline electric field interactions is expected to drive various exotic quantum states. Many theoretical proposals were made in the last decade including the prediction of possible superconductivity in square-lattice iridates emerging as a sister system to high-Tc cuprates, which however met only limited experimental confirmation. One can, therefore, raise a general question: To what extent is the low-energy physics of the quasi-two-dimensional square-lattice iridium oxides different from other transition metal oxides including cuprates? In this thesis we investigate some of the effects which are usually neglected in studies on iridates, focusing on quasi-two-dimensional square-lattice iridates such as Sr2IrO4 or Ba2IrO4. In particular, we discuss the role of the electron-phonon coupling in the form of Jahn-Teller interaction, electron-hole asymmetry introduced by the strong correlations and some effects of coupling scheme chosen to calculate multiplet structure for materials with strong on-site spin-orbit coupling. Thus, firstly, we study the role of phonons, which is almost always neglected in Sr2IrO4, and discuss the manifestation of Jahn-Teller effect in the recent data obtained on Sr2IrO4 with the help of resonant inelastic x-ray scattering. When strong spin-orbit coupling removes orbital degeneracy, it would at the same time appear to render the Jahn-Teller mechanism ineffective. We show that, while the Jahn-Teller effect does indeed not affect the antiferromagnetically ordered ground state, it leads to distinctive signatures in the spin-orbit exciton. Second, we focus on charge excitations and determine the motion of a charge (hole or electron) added to the Mott insulating, antiferromagnetic ground-state of square-lattice iridates. We show that correlation effects, calculated within the self-consistent Born approximation, render the hole and electron case very different. An added electron forms a spin-polaron, which closely resembles the well-known cuprates, but the situation of a removed electron is far more complex. Many-body configurations form that can be either singlets and triplets, which strongly affects the hole motion. This not only has important ramifications for the interpretation of angle-resolved photoemission spectroscopy and inverse photoemission spectroscopy experiments of square lattice iridates, but also demonstrates that the correlation physics in electron- and hole-doped iridates is fundamentally different. We then discuss the application of this model to the calculation of scanning tunneling spectroscopy data. We show that using scanning tunneling spectroscopy one can directly probe the quasiparticle excitations in Sr2IrO4: ladder spectrum on the positive bias side and multiplet structure of the polaron on the negative bias side. We discuss in detail the ladder spectrum and show its relevance for Sr2IrO4 which is in general described by more complicated extended t-J -like model. Theoretical calculation reveals that on the negative bias side the internal degree of freedom of the charge excitation introduces strong dispersive hopping channels encaving ladder-like features. Finally, we discuss how the choice of the coupling scheme to calculate multiplet structure can affect the theoretical calculation of angle-resolved photoemission spectroscopy and scanning tunnelling spectroscopy spectral functions.

Na busca de um melhor entendimento das propriedades eletrônicas e magnéticas dos isolantes topológicos nos deparamos com uma das suas caraterísticas mais marcantes, a existência de estados de superfície metálicos com textura helicoidal de spin os quais são protegidos de impurezas não magnéticas. Na superfície estes canais de spin possuem um potencial enorme para aplicações em dispositivos spintrônicos. Muito há para se fazer e o tratamento via cálculos de primeiros princípios por simulações permite um caráter preditivo que corrobora na elucidação de fenômenos físicos via análises experimentais. Nesse trabalho analisamos as propriedades eletrônicas de isolantes topológicos tais como: (Bi,Sb)$_2$(Te,Se)$_3$, Germaneno e Germaneno funcionalizado. Cálculos baseados em DFT evidenciam a importância das separações entre as camadas de Van der Waals nos materiais Bi$_2$Se$_3$ e Bi$_2$Te$_3$. Mostramos que devido a falhas de empilhamento, pequenas oscilações no eixo de QLs (\\textit{Quintuple Layers}) podem gerar um desacoplamento dos cones de Dirac, além de criar estados metálicos na fase \\textit{bulk} de Bi$_2$Te$_3$. Em se tratando do Bi$_2$Se$_3$ um estudo sistemático dos efeitos de impurezas de metais de transição foi realizado. Observamos que há quebra de degenerescência do cone de Dirac se houver magnetização em quaisquer dos eixos. Além disso se a magnetização permanecer no plano, além de uma pequena quebra de degenerescência, há um deslocamento do mesmo para outro ponto da rede recíproca. No entanto, se a magnetização apontar para fora do plano a quebra ocorre no próprio ponto $\\Gamma$, porém de maneira mais intensa. Importante enfatizar que além de mapear os sítios com suas orientações magnéticas de menor energia observamos que a quebra da degenerescência está diretamente relacionada com a geometria local da impureza. Isso proporciona imagens de STM distintas para cada sítio possível, permitindo que um experimental localize cada situação no laboratório. Estudamos ainda a transição topológica na liga (Bi$_x$Sb$_{1-x}$)$_2$Se$_3$, onde identificamos um isolante trivial e topológico para $x=0$ e $x=1$. Apesar de óbvia a existência de tal transição, detalhes importantes ainda não estão esclarecidos. Concluímos que a dopagem com impurezas não magnéticas proporciona uma boa técnica para manipulação e engenharia de cone nesta família de materiais, de forma que dependendo da faixa de dopagem podemos eliminar a condutividade que advém do \\textit{bulk}. Finalmente estudamos superfícies de Germaneno e Germaneno funcionalizado com halogênios. Usando uma funcionalização assimétrica e com a avalição do invariante topológico $Z_2$ notamos que o material Ge-I-H é um isolante topológico podendo ser aplicado na elaboração de dispositivos baseados em spin. / In the search of a better understanding of the electronic and magnetic properties of topological insulators we are faced with one of its most striking features, the existence of metallic surface states with helical spin texture which are protected from non-magnetic impurities. On the surface these spin channels allows a huge potential for applications in spintronic devices. There is much to do and treating calculations via \\textit{Ab initio} simulations allows us a predictive character that corroborates the elucidation of physical phenomena through experimental analysis. In this work we analyze the electronic properties of topological insulators such as: (Bi, Sb)$_2$(Te, Se)$_3$, Germanene and functionalized Germanene. Calculations based on DFT show the importance of the separation from interlayers of Van der Waals in materials like Bi$_2$Se$_3$ and Bi$_2$Te$_3$. We show that due to stacking faults, small oscillations in the QLs axis (\\textit{Quintuple Layers}) can generate a decoupling of the Dirac cones and create metal states in the bulk phase Bi$_2$Te$_3$. Regarding the Bi$_2$Se$_3$ a systematic study of the effects of transition metal impurities was performed. We observed that there is a degeneracy lift of the Dirac cone if there is any magnetization on any axis. If the magnetization remains in plane, we observe a small shift to another reciprocal lattice point. However, if the magnetization is pointing out of the plane a lifting in energy occurs at the very $ \\Gamma $ point, but in a more intense way. It is important to emphasize that in addition to mapping the sites with their magnetic orientations of lower energy we saw that the lifting in energy is directly related to the local geometry of the impurity. This provides distinct STM images for each possible site, allowing an experimental to locate each situation in the laboratory. We also studied the topological transition in the alloy (Bi$_x$Sb$_{1-x}$)$_ 2$Se$_3$, where we identify a trivial and topological insulator for $x = 0$ and $x = 1$. Despite the obvious existence of such a transition, important details remain unclear. We conclude that doping with non-magnetic impurities provides a good technique for handling and cone engineering this family of materials so that depending on the range of doping we can eliminate conductivity channels coming from the bulk. Finally we studied a Germanene and functionalized Germanene with halogens. Using an asymmetrical functionalization and with the topological invariant $Z_2$ we noted that the Ge-I-H system is a topological insulator that could be applied in the development of spin-based devices.

Craniofaciossinostose sindrômica (CS) é uma desordem congênita associada às mutações dos genes FGFR1, FGFR2 e FGFR3. Ocasiona uma fusão prematura das suturas craniofaciais, levando à deficiência no crescimento do crânio e terço médio da face. A severidade dos sintomas relacionados à hipertensão intracraniana, aparelho respiratório (síndrome da hipopneia-apneia do sono) e ocular (órbitas rasas, proptose ocular, exorbitismo e falta de proteção do globo ocular), são parâmetros para indicar o procedimento cirúrgico. A tomografia-3D é uma opção atual e pouco utilizada para avaliar os volumes orbitais e a magnitude dos avanços craniofaciais e seus vetores; esse método permite melhor definição das estruturas anatômicas sem distorção das imagens, promovendo uma avaliação adequada dos resultados. Os objetivos do presente estudo foram avaliar os volumes orbitais, os avanços craniofaciais e seus vetores nas osteotomias Le Fort III e Monobloco com uso de aparelhos distratores, a correlação entre os avanços craniofaciais e a variação dos volumes orbitais e determinar a eficácia dos avanços craniofaciais por meio da comparação com índices normais de volumes orbitais. No período de janeiro de 2001 a dezembro de 2012, foram selecionados 20 pacientes submetidos ao alongamento ósseo gradual do terço médio da face, divididos em dois grupos. Grupo LF (n = 9), submetidos à osteotomia Le Fort III e Grupo MB (n = 11), submetidos à osteotomia frontofacial monobloco. A avaliação constou da revisão de prontuários e exames tomográficos, em que foram mensurados o volume orbital pela segmentação de imagens no programa InVesalius e modelagem 3D no programa Magics, e a magnitude dos avanços craniofaciais, e seus vetores, foram medidos no programa Rhinoceros. Os resultados foram submetidos à análise estatística: teste t- Student e ANOVA. No Grupo MB, houve aumento de 8,94 mm3 e 9,84 mm3 para a variação do volume orbital, nas órbitas direita e esquerda, respectivamente; no Grupo LF: 5,70 mm3 e 5,77 mm3, respectivamente, para esses parâmetros. A resultante do avanço médio, para a órbita direita e esquerda no Grupo LF foi 11,36 ± 3,80 mm e 11,11 ± 3,45 mm, respectivamente; já no Grupo MB, foi 14,22 ± 4,12 mm e 14,48 ± 4,49 mm, respectivamente. A correlação entre a resultante do avanço e a variação dos volumes orbitais foi significante no Grupo LF e para a órbita esquerda no Grupo MB. Em conclusão, o procedimento cirúrgico foi eficaz, tanto para o Grupo LF como para o Grupo MB, pois, houve aumento estatisticamente significativo do volume orbital no período pós-operatório; não houve diferença estatisticamente significativa, na avaliação da simetria, entre os volumes orbitais pós-operatórios, direito e esquerdo. Ainda, não houve diferença estatisticamente significante entre os volumes orbitais pósoperatórios quando comparados aos índices de normalidade / Syndromic craniofacial synostosis (CS) is a congenital disorder, which is most often, an autosomal dominant mutation associated to FGFR1, FGFR2 and FGFR3 genes. It causes a premature fusion of craniofacial sutures, leading to deficiency in skull growth and middle-third of the face. The severity of the intracranial hypertension related, respiratory syndrome (hypopneaapnea) and eye (shallow orbits, ocular proptosis, exorbitism and lack of protection of the eyeball) symptoms, are parameters that indicate the surgical procedure. Distraction osteogenesis of the middle-third of the face is currently the chosen technique for the treatment of patients with Craniofacial Synostosis syndrome candidates for the advancement of the middle-third of the face. The 3D-tomography is a current option and seldom used for this purpose; this method allows better definition of anatomical structures without image distortion, providing a more accurate assessment of the results. The objectives of the present study, were to assess quantitatively the craniofacial advancement and its vectors through 3D tomographic images, the osteotomy Le Fort III and Monobloc with use of distractor devices; Also, to evaluate the correlation between the craniofacial advances and the variation of orbital volumes and determine the effectiveness of craniofacial advances through the comparison with normal levels of orbital volumes. From January 2001 to December 2012, 20 patients underwent distraction osteogenesis of the middle-third of the face, divided into two groups. LF group (n = 9) underwent a Le Fort III osteotomy and MB group (n = 11) underwent a monobloc frontalfacial osteotomy. The evaluation consisted of the reviewing of the records and tomographic exams; measured is the orbital volume by image segmentation on the InVesalius software and 3D modeling on Magics software and the magnitude of facial advances, and their vectors, were measured on Rhinoceros software. The results were subject to statistical analysis: t-Student test and ANOVA. In the MB group, there was an increase of 8.94 mm3 and 9.84 mm3 for the variation of the orbital volume, the right and left orbits, respectively; in Group LF: 5.70 mm3 and 5.77 mm3 for these parameters. The resulting of average advance, for right and left orbit in Group LF was of 11.36 ± 3.80 mm, 11.11 ± 3.45mm, respectively; as for group MB it was 14.22 ± 4.12 mm and 14.48 ± 4.49 mm, respectively. Correlation between the results from the progress and the variation of orbital volume was significant in Group LF and left orbit in MB Group. In conclusion, the surgical procedure was effective for both the LF group as for the MB Group because: there was a statistically significant increase in orbital volume on the postoperative period; there was no statistically significant difference in the evaluation of symmetry between the postoperative period left and right orbital volumes. Still, there was no statistically significant difference between the postoperative orbital volumes when compared to normal ranges

L'objectif de ce travail est de décrire des modélisations des points de vue et des changements de points de vue d'images d'un objet planaire dans les algèbres de Clifford conformes. Nous généralisons le modèle conforme de l'espace euclidien à travers une famille à deux paramètres d'horosphère, chacune d'entre elles étant plongée dans un espace vectoriel réel de dimension 4 muni d'une métrique équivalente à la métrique de Minkowski. Nous décrivons par la suite deux approches pour mettre en œuvre ces modèles conformes généralisés pour les représentations d'images. L'idée de base est d'encoder les distorsions perspectives de l'objet causées par la variation du paramètre de latitude de la caméra au travers des paramètres d'une horosphère. La première approche consiste à considérer les horosphères de l'espace de Minkowski de dimension 4 pour encoder les points de vue. Les changements de points de vue sont alors linéarisés à travers un groupe de transformations linéaires et conformes de cet espace. Cette approche est ensuite généralisée en décrivant les points de vue à travers les objets d'un groupoïde dont les morphismes sont des diagrammes commutatifs qui représentent les changements de points de vue. Ainsi, une image conforme est décrite par une application définie sur une horosphère à deux paramètres. L'action du groupoïde sur l'ensemble des images conformes nous conduit à associer à tout objet planaire l'orbite de toutes ses images conformes obtenues à partir de tous les points de vue. / Our purpose in this work is to introduce representations of image viewpoints and viewpoint changes of a planar object in conformal Clifford algebras. Our important preliminary contribution is a generalization of the conformal model of the Euclidean space through a two-parameter family of horospheres. Each one of these is embedded into a real vector space of dimension 4 equipped with a metric equivalent to the Minkowski metric. We describe two approaches that make use of these generalized conformal models for image representations. These are based on modelings of perspective distortions of the object caused by a variation of the latitude angle of the camera. First, we model the image viewpoints by the horospheres of the Minkowski space of dimension 4. In this setting, the viewpoint changes are linearized through a group of linear conformal transformations of this space. This approach is generalized by describing the viewpoints through the objects of a groupoid whose morphisms are commutative diagrams that model the viewpoint changes. A conformal image is then described as a map defined on a horosphere. The action of the groupoid on the set of conformal images leads us to associate with every planar object the orbit of its conformal images from all viewpoints.

Pour X un espace topologique, l'algèbre de Lie de Malcev de son groupe fondamental (ou algèbre de Lie de Malcev de X) fait partie des invariants étudiés en homotopie rationnelle. Un espace est dit 1-formel si cette algèbre de Lie est quadratique. Les connexions de type Knizhnik-Zamolodochikov peuvent permettre d'établir des résultats de "formalité " des espaces de configurations de points sur les surfaces. On s'intéresse à une famille d'espaces X qui sont des espaces de configurations de points sur la sphère, tordus par l'action d'un groupe fini d'homographies. On étudie le groupe fondamental de X et on construit une connexion de type Knizhnik-Zamolodochikov qui permet de calculer l'algèbre de Lie de Malcev de X et de démontrer sa 1-formalité. / The Malcev Lie algebra of the fundamental group of X (or Macev Lie algebra of X) is an algebraic invariant of the space X studied in rational homotopy theory. The space X is 1-formal if its Malcev algebra is quadratic. One can use Knizhnik–Zamolodchikov-type connections to obtain "formality" (1-formality or filtered formality) results for configuration spaces of surfaces. In the thesis we consider a family of orbit configuration spaces X of the complex projective line associated to finite finite groups of homographies. We study the fundamental group of X and constuct Knizhnik– Zamolodchikov-type connections. This allows us to give a presentation of the Malcev Lie algebra of X and to prove the 1-formality of X.

Alors que les individus dans la société contemporaine sont unis non par une propriété mais par un devoir et par une dette, par un manque, par une limite prenant la forme d’une charge pour celui qui en est affecté, la postmodernité rend à la mort et à l’absence toute sa densité. À travers la répétition, entre jubilation et désespérance, les artistes figurent la temporalité de l’épreuve par une écriture qui travaille l’instant. Ils racontent ces évènements infimes qui sont les plus fragiles, les plus précaires, ayant pourtant une forte efficacité. Il s’agira ici d’étudier les nouvelles postures devant l’événement historique, quand l’artiste se tient au plus singulier. / While individuals in contemporary society are united not by property but by a duty and a debt, a lack, by a limit taking the shape of a responsibility for the one who is affected, postmodernism returns to death and absence all its density. Through repetition, between jubilation and despair, the artist represents the temporality of the event. His writing works the moment. He tells these tiny events that are the most fragile, the most precarious, having nevertheless a strong efficiency. This thesis will try to study the new postures in front of the historic event, when the artist stands in the most singular.

Ultrafast dynamical processes in magnetic systems have become the subject of intense research during the last two decades, initiated by the pioneering discovery of femtosecond laser-induced demagnetization in nickel. In this thesis, we develop theory for fast and ultrafast magnetization dynamics. In particular, we build relativistic theory to explain the magnetization dynamics observed at short timescales in pump-probe magneto-optical experiments and compute from first-principles the coherent laser-induced magnetization. In the developed relativistic theory, we start from the fundamental Dirac-Kohn-Sham equation that includes all relativistic effects related to spin and orbital magnetism as well as the magnetic exchange interaction and any external electromagnetic field. As it describes both particle and antiparticle, a separation between them is sought because we focus on low-energy excitations within the particle system. Doing so, we derive the extended Pauli Hamiltonian that captures all relativistic contributions in first order; the most significant one is the full spin-orbit interaction (gauge invariant and Hermitian). Noteworthy, we find that this relativistic framework explains a wide range of dynamical magnetic phenomena. To mention, (i) we show that the phenomenological Landau-Lifshitz-Gilbert equation of spin dynamics can be rigorously obtained from the Dirac-Kohn-Sham equation and we derive an exact expression for the tensorial Gilbert damping. (ii) We derive, from the gauge-invariant part of the spin-orbit interaction, the existence of a relativistic interaction that linearly couples the angular momentum of the electromagnetic field and the electron spin. We show this spin-photon interaction to provide the previously unknown origin of the angular magneto-electric coupling, to explain coherent ultrafast magnetism, and to lead to a new torque, the optical spin-orbit torque. (iii) We derive a definite description of magnetic inertia (spin nutation) in ultrafast magnetization dynamics and show that it is a higher-order spin-orbit effect. (iv) We develop a unified theory of magnetization dynamics that includes spin currents and show that the nonrelativistic spin currents naturally lead to the current-induced spin-transfer torques, whereas the relativistic spin currents lead to spin-orbit torques. (v) Using the relativistic framework together with ab initio magneto-optical calculations we show that relativistic laser-induced spin-flip transitions do not explain the measured large laser-induced demagnetization. Employing the ab initio relativistic framework, we calculate the amount of magnetization that can be imparted in a material by means of circularly polarized light – the so-called inverse Faraday effect. We show the existence of both spin and orbital induced magnetizations, which surprisingly reveal a different behavior. We establish that the laser-induced magnetization is antisymmetric in the light’s helicity for nonmagnets, antiferromagnets and paramagnets; however, it is only asymmetric for ferromagnets.

Abstract Image acquisition devices are always subject to physical limitations that often manifest as distortions in the appearance of the captured image. The most common types of distortions can be divided into two categories: geometric and radiometric distortions. Examples of the latter ones are: changes in brightness, contrast, or illumination, sensor noise and blur. Since image blur can have many different causes, it is usually not convenient and also computationally expensive to develop ad hoc algorithms to correct each specific type of blur. Instead, it is often possible to extract a blur-invariant representation of the image, and utilize such information to make algorithms that are insensitive to blur. The work presented here mainly focuses on developing techniques for the extraction and the application of blur-invariant operators. This thesis contains several contributions. First, we propose a generalized framework based on group theory to constructively generate complete blur-invariants. We construct novel operators that are invariant to a large family of blurs occurring in real scenarios: namely, those blurs that can be modeled by a convolution with a point-spread function having rotational symmetry, or combined rotational and axial symmetry. A second important contribution is represented by the utilization of such operators to develop an algorithm for blur-invariant translational image registration. This algorithm is experimentally demonstrated to be more robust than other state-of-the-art registration techniques. The blur-invariant registration algorithm is then used as pre-processing steps to several restoration methods based on image fusion, like depth-of-field extension, and multi-channel blind deconvolution. All the described techniques are then re-interpreted as a particular instance of Wiener deconvolution filtering. Thus, the third main contribution is the generalization of the blur-invariants and the registration techniques to color images, by using respectively a representation of color images based on quaternions, and the quaternion Wiener filter. This leads to the development of a blur-and-noise-robust registration algorithm for color images. We observe experimentally a significant increase in performance in both color texture recognition, and in blurred color image registration. / Tiivistelmä Kuvauslaitteet ovat aina fyysisten olosuhteiden rajoittamia, mikä usein ilmenee tallennetun kuvan ilmiasun vääristyminä. Yleisimmät vääristymätyypit voidaan jakaa kahteen kategoriaan: geometrisiin ja radiometrisiin distortioihin. Jälkimmäisestä esimerkkejä ovat kirkkauden, kontrastin ja valon laadun muutokset sekä sensorin kohina ja kuvan sumeus. Koska kuvan sumeus voi johtua monista tekijöistä, yleensä ei ole tarkoitukseen sopivaa eikä laskennallisesti kannattavaa kehittää ad hoc algoritmeja erityyppisten sumeuksien korjaamiseen. Sitä vastoin on mahdollista erottaa kuvasta sumeuden invariantin edustuma ja käyttää tätä tietoa sumeudelle epäherkkien algoritmien tuottamiseen. Tässä väitöskirjassa keskitytään esittämään, millaisia eri tekniikoita voidaan käyttää sumeuden invarianttien operaattoreiden muodostamiseen ja sovellusten kehittämiseen. Tämä opinnäyte sisältää useammanlaista tieteellistä vaikuttavuutta. Ensiksi, väitöskirjassa esitellään ryhmäteoriaan perustuva yleinen viitekehys, jolla voidaan generoida sumeuden invariantteja. Konstruoimme uudentyyppisiä operaattoreita, jotka ovat monenlaiselle kuvaustilanteessa ilmenevälle sumeudelle invariantteja. Kyseessä ovat ne rotationaalisesti (ja/tai aksiaalisesti) symmetrisen sumeuden lajit, jotka voidaan mallintaa pistelähteen hajaantumisen funktion (PSF) konvoluutiolla. Toinen tämän väitöskirjan tärkeä tutkimuksellinen anti on esitettyjen sumeuden invarianttien operaattoreiden hyödyntäminen algoritmin kehittelyssä, joka on käytössä translatorisen kuvan rekisteröinnissä. Tällainen algoritmi on tässä tutkimuksessa osoitettu kokeellisesti johtavia kuvien rekisteröintitekniikoita robustimmaksi. Sumeuden invariantin rekisteröinnin algoritmia on käytetty esiprosessointina tässä tutkimuksessa useissa kuvien restaurointimenetelmissä, jotka perustuvat kuvan fuusioon, kuten syväterävyysaluelaajennus ja monikanavainen dekonvoluutio. Kaikki kuvatut tekniikat ovat lopulta uudelleen tulkittu erityistapauksena Wienerin dekonvoluution suodattimesta. Näin ollen tutkimuksen kolmas saavutus on sumeuden invarianttien ja rekisteröintiteknikoiden yleistäminen värikuviin käyttämällä värikuvien kvaternion edustumaa sekä Wienerin kvaternion suodatinta. Havaitsemme kokeellisesti merkittävän parannuksen sekä väritekstuurin tunnistuksessa että sumean kuvan rekisteröinnissä.

Ce travail consiste en l'étude de phénomènes optomécaniques en d'interaction spin-orbite de la lumière, en utilisant des milieux inhomogènes et anisotropes comme systèmes modèles, différents types de systèmes matériels étant considérés en pratique. En particulier,nous avons utilisé des défauts de cristaux liquides nématiques pour lesquels nous avons identifié expérimentalement d'un couple optique de nature spin-orbite conduisant à des modifications de champ d'orientation moléculaire du cristal liquide. Aussi, grâce à l'utilisation de verres nanostructurés artificiellement permettant un contrôle de l'interaction spin-orbite à la demande,nous mettons en évidence un phénomène de couple optique inverse qui est l'analogue angulaire des forces optiques dites négatives. Cet effet optomécanique contre-intuitif est démontré expérimentalement, d'une manière indirecte, grâce à la mise en place de diverses expériences de décalage en fréquence Doppler associées aux degrés de liberté de rotation. Enfin, nous présentons nos tentatives en vue de réaliser expérimentalement l'observation directe d'un couple optique inverse. Plusieurs options sont envisagées, qui comprennent à la fois des approches à base de matériaux métalliques ou diélectriques. De manière générale, cela implique la miniaturisation des systèmes considérés, ce qui est effectué à la fois à l'échelle millimétrique et micrométrique. / This work focuses on angular optomechanics driven by the spin-orbit interaction of light, using inhomogeneous and anisotropic media as model systems and different kinds of such material systems are considered in practice. In particular, we use nematic liquid crystal defects and report on the direct experimental observation of spin-orbit optical radiation torque that leads to distortion of molecular orientation pattern of the defects. Then, by using solid-state spin-orbit couplers of arbitrary order made of artificially nanostructured glasses, we unveil an optical torque reversal phenomenon that is the angular counterpart of so-called optical negative forces. This counterintuitive optomechanical effect is experimentally retrieved, in an indirect manner, via rotational Doppler frequency shift experiments. Finally, we report on our attempts to build up an experimental framework allowing the direct observation of optical torque reversal. Several options are considered, which include both metallic and dielectric approaches and involve sample miniaturization that has been explored at the millimeter and micrometer scale.

Asymmetrically sandwiched ferromagnetic thin films display a large number of spin-orbit effects, including the Dzyaloschinsii-Moriya interaction (DMI), spin-orbit torques (SOT) and magnetoresistance (MR) effects. Their concurrence promises the implementation of interesting magnetic structures like skyrmions in future memory and logic devices. The complex interplay of various effects originating from the spin-orbit coupling and their dependencies on the microstructural details of the material system mandates a holistic characterization of its properties. In this PhD thesis, a comprehensive study of the spin-orbit effects in a chromium oxide/cobalt/platinum trilayer sample series is presented. The determination of the complete micromagnetic parameter set is based on a developed measurement routine that utilizes quasistatic methods. The unambiguous quantification of all relevant constants is crucial for the modeling of the details of magnetic structures in the system. In this context the necessity of a strict distinction of magnetic objects, that are stabilized by magnetostatics or the DMI, was revealed. Furthermore, a sample layout was developed to allow for the simultaneous quantification of the magnitudes of SOTs and MR effects from nonlinear magnetotransport measurements. In conjunction with a structural characterization, the dominating dependence of the effect magnitudes on microstructural details of the systems is concluded. Precisely characterized systems establish a solid groundwork for further investigations that are needed for viable skyrmion-based devices.