Rozprawy doktorskie na temat „Electric dipole spin resonance”

Alors qu’âgée d’à peine plus d’un siècle, la physique quantique est devenue technologique. Son représentant le plus omniprésent est le transistor, en tant que brique élémentaire des appareils électroniques. Les progrès en fabrication à l’échelle nanométrique ont engendré une croissance exponentielle de sa densité dans les circuits microélectroniques. Une fois au nanomètre, des effets quantiques inévitables empêchent de miniaturiser davantage. Des modèles alternatifs sont étudiés pour contourner cet obstacle, dont la plateforme « complementary metal-oxide semiconductor fully depleted silicon-on-insulator” (CMOS FD-SOI).En parallèle de ces développements, la physique quantique a donné naissance à une nouvelle génération d’innovation technologique, grâce à la capacité de contrôler la matière à l’échelle de la particule unique. Isoler une particule dans un environnement suffisamment calme donne accès à ses propriétés de superposition et d’intrication. Exploiter ces phénomènes pour le traitement de l’information conduirait au changement de paradigme du calcul quantique, qui promet de résoudre des problèmes classiquement intractables. Plusieurs acteurs concourent à la meilleure implémentation d’un bit quantique (ou « qubit ») et tous se heurtent au défi de passer de quelques qubits académiques à un processeur industriel. Parmi eux, les électrons piégés dans des structures silicium sont prometteurs du fait de leur exposition réduite aux noyaux magnétiques et au couplage spin-orbite, et de la possibilité de les purifier des noyaux de spin non nul. De plus, leur compatibilité avec le savoir-faire microélectronique donne l’espoir du passage à l’échelle. Dans cette thèse, nous étudions des électrons uniques piégés dans des boites quantiques définies dans des transistors CMOS FD-SOI. Nous nous intéressons en particulier aux aspects de « bruit » dans leur contrôle et leur lecture.Tout d’abord, nous démontrons la manipulation cohérente d’un spin d’électron CMOS par résonance magnétique médiée électriquement. Un microaimant déposé sur la puce CMOS génère un champ magnétique inhomogène. Exciter le déplacement de l’électron dans ce gradient par les tensions de grille lui fait sentir un champ magnétique oscillant, permettant des rotations du spin avec une fréquence Rabi de 1MHz et un temps de déphasage de 500ns. Nous attribuons ces performances limitées à un nombre fini de fluctuateurs à deux niveaux et aux dimensions réduites des boites quantiques en CMOS. L’enveloppe Rabi et le déphasage rapide sont caractéristiques de l’interaction avec les spins nucléaires. Cependant, découpler dynamiquement l’électron de cette gamme de fréquence offre des temps de cohérence à l’état de l’art, limités par le bruit de charge, en accord avec de simples mesures électriques à basse fréquence. Ces résultats suggèrent la pertinence de la purification isotopique pour s’affranchir du bruit hyperfin.Ensuite, nous nous intéressons au bruit de lecture de ces électrons. L’objectif était d’évaluer la pertinence d’un amplificateur paramétrique à ondes progressives (TWPA) dans la chaine de lecture radiofréquence des dispositifs. Fabriquer des résonateurs sur la puce CMOS a permis de réduire leur capacité parasite et de réaliser des mesures par réflectométrie dans la gamme 3-4GHz, plus près du régime habituel du TWPA. Même pompé loin de son gap, le TWPA montre des figures de mérite nominales, et une résilience à un champ magnétique typique des expériences de qubits de spin. Son haut point de compression à -100dBm, sa bande passante large (2GHz) et réglable et son bruit ajouté proche de la limite quantique permettent plus de 10dB d’amélioration du rapport signal-sur-bruit dans la lecture de transitions de charge interdot, et une lecture multiplexée dans un dispositif à six grilles. Cette compatibilité entre un amplificateur supraconducteur à large bande et des dispositifs CMOS FD-SOI multi-grilles est encourageante en vue d’expériences à plus grande échelle
While being a bit more than a century old, quantum physics have become technological. The most ubiquitous instance of the use of quantum physics is the transistor, as the building block of modern computing devices. Progress in nanoscale fabrication has fostered an exponential increase of transistor density In microelectronics circuits. Once in the nanometer range, unavoidable quantum effects tamper further miniaturization. Alternative transistor designs are being developed to mitigate this showstopper. The complementary metal-oxide-semiconductor (CMOS) fully-depleted silicon-on-insulator (FD-SOI) platform is one of them.In parallel to these developments, quantum physics spawned a new generation of technological innovation, thanks to the ability to control matter at the single particle level. Isolating elementary particles in a quiet environment gives access to their superposition and entanglement properties. Using these to process information would realize the quantum computing paradigm shift, where classically intractable problems are promised to come at reach. Many candidates are racing for the best implementation of a quantum bit (or “qubit”) and all of them are facing the challenge to up-scale their architecture from a few lab qubits to an industrial processor. Among them, electrons trapped in silicon structures offer promising prospects thanks to their reduced exposure to magnetic nuclei and spin-orbit interaction, and to the possibility to purify away non-zero nuclear spins. Moreover, the expected compatibility of silicon structures with microelectronics know-how gives hopes for scalability. In this thesis, we study single electrons trapped in gate-defined quantum dots formed in CMOS FD-SOI transistors. We investigate on how to improve their use as qubits, focusing on experimental noise aspects.First, we demonstrate coherent manipulation of a single CMOS electron spin with electrically driven spin resonance. A micromagnet is patterned directly on top of the CMOS chip, creating an inhomogeneous magnetic field. Driving the electron motion inside this gradient with the available electric gates makes it feel an effective oscillating magnetic field, and enables single qubit operations, with a relatively low 1 MHz Rabi frequency and short 500 ns dephasing time. This limited performance is attributed to a finite number of two-level fluctuators and smaller quantum dot sizes compared to other silicon architectures. The shape of the Rabi decay and the sub-µs dephasing time are characteristic of hyperfine interaction with spinful nuclei. However, dynamically decoupling the electron spin from this frequency range showed state-of-the-art coherence times and performance limited by charge noise, in accordance with simple charge sensor measurements at low frequencies. These results point towards the relevance of isotopic purification to avoid hyperfine-induced dephasing in CMOS FD-SOI devices.After focusing on qubit control, a second part of this thesis deals with readout noise. The objective was to demonstrate the use of a traveling-wave parametric amplifier (TWPA) in the amplification chain of radio-frequency readout of CMOS devices. Patterning inductors on the CMOS chip reduced the parasitic capacitance of our resonators and enabled to perform lumped-element reflectometry in the 3-4 GHz range, closer to usual TWPA operating regimes. Even when being pumped far from its gap, the TWPA shows nominal figures of merit, and a resilience to magnetic fields typical for spin qubit experiments. Its high -100dBm compression point, wide and tunable 2 GHz bandwidth and quantum-limited added noise enabled to get more than 10dB signal-to-noise ratio improvement on interdot charge transitions in our devices, and to multiplex interdot readout in a 6-gate device. This compatibility between a large bandwidth superconducting amplifier and multi-gate CMOS FD-SOI quantum devices is promising towards CMOS electron spin qubit experiments at larger scale

Quantum information processing (QIP) has the potential to reduce the complexity of many classically ‘hard’ computational problems. To implement quantum information algorithms, a suitable physical quantum computer architecture must be identified. One approach is to store quantum information in the electron spins of an array of paramagnetic N@C₆₀ endohedral fullerene molecules, using the electron-electron dipolar interaction to permit the formation of the entangled quantum states needed to implement QIP. This thesis explores two different chemical methods to create two-spin centre arrays that contain N@C₆₀. The first method uses a double 2,3 dipolar cycloaddition reaction to a dibenzaldehyde-terminated oligo-p-phenylene polyethynylene (OPE) unit , to create an (S_3/2, S_3/2) N@C₆₀-N@C₆₀ dimer with a fixed spin centre separation of 2.7 nm. The second approach is via a self-assembly scheme in which a Lewis base functionalised N@C₆₀ molecule coordinates to an antiferromagnetic metallic ring magnet to form a (S_3/2, S_3/2) two-spin centre N@C₆₀-Cr₇Ni system with an inter-spin separation of 1.4 nm. In both systems, a significant perturbation of the electron spin transition energies is observed using CW ESR, this perturbation is shown to be well accounted for by the inclusion of an electron-electron dipolar coupling term in the electron spin Hamiltonians. To create entanglement in an ensemble of two-spin centre molecules, the dipolar coupling interaction must lie within a narrow distribution. To achieve this not only the separation but also the orientation of the inter-spin axis with respect to the applied magnetic field must be controlled for which a method of macroscopic alignment is required. The potential of using a uniaxially drawn liquid crystal elastomer to exert uniaxial order on fullerene dimers is tested, finding that the degree of alignment is insufficient, possibly a result of the propensity for the fullerene molecules to phase separate from the elastomer. This phase separation is shown to restrict N@C₆₀ phase coherence lifetime to 1.4 µs at 40 K due to instantaneous spin diffusion. The electron spin environment of both N@C₆₀ and an N@C₆₀-C₆₀ dimer in a polymer matrix is examined using polystyrene as the host matrix. By deuteration of the polystyrene matrix, a maximum phase coherence lifetimes of 48 µs and 21 µs are measured for the N@C₆₀ and N@C₆₀-C₆₀ dimer, respectively. The concept of reading out the electron spin state of N@C₆₀ molecules by coupling it to a spin system that can be probed using optically detected magnetic resonance (ODMR) such as an NV- centre has been previously suggested. To this end, the photostability of N@C₆₀ under 637 nm laser illumination has been examined in solution. The effect of the presence of an atmospheric concentration of oxygen is striking, affording a 57-fold retardation in the photodecomposition of N@C₆₀ compared to a degassed solution. When ambient oxygen is present, the average number of excitations that are required to cause decomposition is ≈60000. Finally, for future UV photophysics experiments involving N@C₆₀, the best solvent to use was found to be decalin, finding that it significantly slowed decomposition of N@C₆₀ in both ambient and degassed solutions. The conclusions of this work make a significant contribution to the field of QIP with N@C₆₀, showing that there is a bright future for N@C₆₀.

The biological function of macromolecules such as protein, DNA, and RNA depends on their folding and on the relative movements of domains with dimensions of a few nanometers. This length scale can be accessed by distance measurements between paramagnetic spin centers employing Electron Paramagnetic Resonance (EPR) pulsed dipolar spectroscopy (PDS) techniques. In order to use this spectroscopic methods, the biomolecule has to contain either stable or transient paramagnetic centers, which can be metal ions or clusters, amino acid radicals, or organic cofactor radicals. If the biomolecule is diamagnetic, it can be spin-labeled with nitroxides or a diamagnetic metal may be substituted with a paramagnetic one. Nitroxides are the most employed spin probes in PDS, especially for structural studies in proteins were they can be attached to specific sites following a protocol of mutagenesis and site-directed spin labeling (SDSL) on cysteine residues. However, the introduction of a spin label can modify the structure around the labeling site and in some regions it may even interfere with the correct folding. For this reason, exploiting endogenous probes i.e. paramagnetic centers which are naturally present in the protein, represents an primary task in PDS. Indeed, PSD has been entatively performed on various classes of proteins naturally containing metal base-prosthetic groups such as and low-spin ferric heme centers, iron-sulfur cluster, Mn clusters for which mainly the ¢mS Æ §1/2 transition can be selected. Utilizing endogenous probes for EPR detection only causes minimal functional perturbation to the macromolecules. Another advantage is that they are firmly anchored in the protein and, therefore, are not fraught with the problem of flexible linkers as the commonly used spin labels. In recent years photoexcited triplet state of porphyrin has been introduced in the selection of spin labels for PDS applications. In their ground state, these chromophores are diamagnetic and thus EPR-silent, but, upon laser photoexcitation, their triplet state can be populated via intersystem crossing from the lowest excited singlet state, generating in this way the paramagnetic center. The inter-system crossing mechanism makes the population of the triplet sublevels different from the Boltzmann distribution, significantly enhancing the intensity of their EPR signals. Moreover porphyrin-derivative groups are suitable to be exploited as endogenous probes because are present in numerous systems such as heme-protein and photosynthetic proteins. The orthogonal labeling method, based on the use of spectroscopically nonidentical labels which can be addressed selectively in the EPR experiment, is attracting increasing interest in the spectroscopic community. Triplet states work very efficiently as orthogonal labels, adding to the spectroscopic selectivity the advantage of behaving as photoinduced spin probes. This feature allows to perform PDS in the presence of light excitation to measure intramolecular triplet-nitroxide distances or in the absence of light excitation revealing intermolecular nitroxide-nitroxide interactions. While the feasibility of the PDS experiment had already been demonstrated for a photoexcited porphyrin moiety interacting with a nitroxide radical [Di Valentin, M.; Albertini, M.; Zurlo, E.; Gobbo, M. and Carbonera, D. J. Am. Chem. Soc., 2014, 136, 6582 -6585], the accuracy of the new labeling approach for distance determination, and the theoretical frame describing the behavior of polarized high-spin systems for application in dipolar techniques were still laking. In this thesis work a complete spectroscopic and theoretical characterization of photoexcited triplet state probes has been carried out. The reliability and versatility of such spin labels has been tested employing different dipolar pulse schemes and exploiting diverse chromophores for the photogeneration of the paramagnetic center, both in peptide-based model systems and in protein belonging to different classes. The study has been completed with an exhaustive theoretical description. The reliability and the accuracy of the new labeling approach has been demonstrated by measuring the dipolar traces of a spectroscopic ruler composed by a-helix peptides of increasing length, labeled with a porphyrin chromophore, that upon photoexcitation gives the EPR-active species, and a nitroxide artificial amino acid. The good correlation between the distances obtained by experimental PDS data and calculation, is used to asses the accuracy of the new labeling approach. In PDS, there are different pulse sequences that exploits diverse mechanisms to induce the dipolar oscillations. Such pulse schemes have been tested on the triplet state in order to classify the performances of the various PDS techniques with the novel labeling approach. The availability of different light-induced PDS sequences increases the versatility of triplet state probes allowing to select case by case the pulse scheme that guarantees the best signal-to-noise ratio. The new labeling approach has been extended to two paradigmatic proteins: the light-harvesting complex Peridinin-Chlorophyll a-Protein fromAmphidinium Cartarae and the human Neuroglobin belonging to the globins family where the endogenous prosthetic groups have been exploited to photo-generated the triplet state. In the photosynthetic protein the dipolar trace arising from the interaction between the triplet state of one of the carotenoids in the photoactive site and a nitroxide, introduced via site-directed spin labeling, have been measured. This allowed to identify the pigment involved in the photoprotective mechanism and demonstrated that, not only porphyrin-derivatives, but also other chromophores can be used as spin probes. In human neuroglobin the Zn-substitution of the heme has allowed to populate the triplet state of the Zn protoporphyrin IX and successfully measure the dipolar trace proving the applicability of this labeling procedure on the class of hemeproteins. The full characterization of triplet state probes has been completed with a theoretical study based on the density matrix formalism. First, the analytic formula describing the modulation of the dipolar trace for a simplified radical-triplet state system has been obtained, highlighting a time an analogous dependence to the radical-radical case. Subsequently, a program for time-domain numerical calculation of radical-triplet state dipolar traces has been implemented and employed for a quantitative characterization of triplet state probes in PDS.
Il ruolo di molte macromolecole di interesse biologico come ad esempio proteine ed acidi nucleici, dipende dalla loro struttura tridimensionale e da movimenti di domini dell’ordine di pochi nanometri. La spettroscopia paramagnetica elettronica (EPR) ed in particolare le tecniche di spettroscopia impulsata dipolare (PDS) costituiscono lo strumento ideale per studiare sistemi di quest’ordine di grandezza. Tuttavia, per poter utilizzare tecniche PDS nella caratterizzazione di bio-macromolecole, queste devono contenere centri paramagnetici come ad esempio ioni o cluster metallici, oppure centri radicalici. Nel caso in cui il sistema sia diamagnetico è necessario quindi inserire delle sonde paramagnetiche o sostituire eventuali metalli diamagnetici con altri metalli EPR-attivi. I radicali nitrossidi sono le sonde di spin più comunemente impiegate nella spettroscopia dipolare, soprattutto per studi in proteina in cui, per introdurre di tali sonde, è possibile seguire un protocollo di mutagenesi sito-specifica seguita da spin labeling diretto alle cisteine. L’inserimento di sonde di spin tuttavia può causare forti modifiche strutturali alla macromolecola o addirittura interferire con il suo corretto folding. Per questo motivo, quando possibile si tenta di sfruttare centri paramagnetici che siano naturalmente presenti in proteina. Sono stati infatti effettuati diversi studi di spettroscopia dipolare in metallo-proteine sfruttando la transizione ¢mS Æ §1/2 del gruppo prostetico contenente il centro metallico. L’utilizzo di tali gruppi prostetici non causa alcuna alterazione strutturale alla molecola, inoltre, diversamente da molte sonde endogene, questi sono strettamente ancorati all’intorno proteico e forniscono quindi informazioni strutturali più accurate. La porfirina in stato di tripletto fotoeccitato è stata di recente introdotta tra la collezione di sonde di spin utilizzabili nelle tecniche PDS. Nel loro stato fondamentale le porfirine sono diamagnetiche e pertanto EPR silenti, ma in seguito a fotoeccitazione laser possono popolare tramite inter-system crossing lo stato di tripletto eccitato a più bassa energia, divetando in tal modo EPR-attive. Il popolamento tramite inter-system crossing fa si che la popolazione dei sottolivelli di tripletto devii dalla distribuzione di Boltzmann, aumentando enormemente l’intensità del segnale EPR di tale specie che vengono per questo motivo definite "polarizzate". Inoltre derivati porfirinici sono presenti in numerosi sistemi naturali, come ad esempio le emoproteine o le proteine conivolte in processi fotosintetici, e ciò li rende particolarmente interessanti per l’utilizzo in spettroscopia dipolare in quanto possono essere sfruttati come sonde endogene. Il labeling ortogonale, basato sull’impiego di sonde di spin spettroscopicalmente distinte che possono essere eccitate selettivamente durante un esperimento EPR, rappresenta un approccio particolarmente vantaggioso nelle tecniche PDS. Gli stati di tripletto fotoeccitato hanno un valore aggiunto come sonde ortogonali perchè aggiungono alla selezione spettrale il fatto di essere sonde foto-indotte. Questa caratteristica fa si che sia possibile misurare distanze intarmolecolari tripletto-nitrossido, applicando la fotoeccitazione laser, e distanze ntermolecolari nitrossido-nitrossido spegnedo invece la fotoeccitazione. Mentre la fattibilità di esperimenti di spettroscopia dipolare applicati a stati di tripletto fotoeccitati era già stata dimostrata precedentemente a questo lavoro di tesi [Di Valentin, M.; Albertini, M.; Zurlo, E.; Gobbo, M. and Carbonera, D. J. Am. Chem. Soc., 2014, 136, 6582 -6585], mancavano completemente indagini in grado di stabilire l’affidabilità e l’accuratezza del nuovo sistema di labeling e un inquadramento teorico in grado di escrivere il comportamento di tali sistemi polarizzati ad alto spin durante l’esperimento PDS. Il lavoro alla base della presente tesi è consistito nella completa caratterizzazione spettroscopica e teorica di questi sistemi di spin. Per verificare l’affidabilità del nuovo approccio, le sonde di tripletto sono state testate con diverse tecniche PDS, e sono stati inoltre utilizzati vari cromofori per la foto-generazione del centro paramagnetico, effettuando l’analisi sia su sistemi modello che in proteina. Lo studio è stato completato con un esaustivo trattamento teorico dei sistemi tripletto-radicale in spettroscopia dipolare. La precisione e l’accuratezza del metodo sono state verificate misurando le tracce dipolari di un righello spettroscopico costituito da una serie di perptidi in ®-elica di lunghezza crescente, ognuno marcato con un cromoforo porfirinico e un radicale nitrossido. L’ottima correlazione trovata tra le distanze ottenute analizzando le tracce sperimentali e i dati strutturali derivanti dai calcoli ha permesso di dimostrare l’affidabilità delle sonde di tripletto nelle tecniche PDS. Attualmente sono disponibili diverse sequenze PDS che sfruttano diversi meccanismi per indurre l’oscillazione dipolare nelle tracce sperimentali. Molte di queste sequenze sono state quindi testate sulla sonda di tripletto in modo da verificarne le prestazioni con le diverse tecniche. La disponibilità di molteplici sequenze PDS e il loro buon funzionamento su sistemi fotoindotti permette di selezionare, a seconda dei casi, lo schema di impulsi che garantisce le migliori prestazioni in termini di rapporto segnale-rumore e ciò dimostra la versitilità delle sonde di tripletto. La nuova metodologia è stata estesa anche a studi in proteina utilizzando come sistemi modello la Peridinin-Chlorophyill a-Protein, appartenente alla classe delle proteine fotosintetiche, e neuroglobina umana, facente parte della famiglia dellle globine. In Peridinin-Chlorophyill a-Protein è stata misurata l’interazione dipolare tra uno dei carotenoidi presenti nel sito attivo e un nitrossido inserito tramite spin labeling, permettendo non solo l’individuazione del pigmento coinvolto nel meccanismo di fotoprotezione, ma espendendo anche l’applicabilità dell’esperimento a cromofori diversi dai derivati porfirinici. Nella neuroglobina umana invece la zinco-sostituzione dell’eme ha permesso di popolare lo stato di tripletto nel gruppo endogeno e dimostrando che la tecnica dipolare fotoindotta può essere utilizzata anche nello studio strutturale di proteine (macromolecole) apparteneneti alla classe delle emoproteine. Infine è stata effettuata anche un’esaustiva caratterizzazione teorica delle sonde di tripletto basata sul formalismo della matrice densità. E’ stata ricavata l’espressione che descrive la modulazione delle tracce dipolari in sistemi tripletto-radicale, che è risultata essere analoga a quella ottenuta per sistemi di due radicali interagenti. Successivamente è stato implementato un programma per il calcolo numerico di tracce dipolari che ha permesso una descrizione quantitativa diversi sistemi tripletto-radicale.

This thesis is concerned with the design and realisation of components for a new state of the art 94GHz Electron Spin Resonance (ESR) spectrometer capable of operating in both pulsed and CW modes. The complete spectrometer is designed to provide phase coherent 1kW peak power sub-nanosecond π/2 pulses having variable duration and repetition rate. The mm-wave response of a paramagnetic sample to these pulses is detected with a superheterodyne detector. Such a system would offer a step change in performance, promising unprecedented resolution and sensitivity. These aims should be compared with the performance of commercial (Bruker) instruments capable of delivering 200mW 30ns π/2 pulses. For this type of system, both the long term (thermal) and short term (phase) stability of oscillators and sources employed are extremely important. Consideration of phase noise, frequency, tunability and power output shows that multiplied sources offer substantial benefits compared to fundamental sources. A delay line discriminator method of phase noise measurement, suitable for use with the low frequency oscillators is described and implemented. This is extended to 94GHz using a down convertor with a quasi-optically stabilised Gunn oscillator. These tools are used to select an optimum oscillator-multiplier combination to produce a low noise 94GHz source. Anew method of pulse generation, which has produced +23dBm peak power 250ps rectangular and 115ps Gaussian envelope phase coherent pulses, is described. These are believed to be the shortest phase coherent pulses at 94GHz available. This system will be used to provide ns pulses suitable for amplification to 1kW using a Klystron amplifier. A heterodyne detector has been constructed which employs the same oscillator/multiplier techniques identified above to produce the required local oscillator signal. It is demonstrated that by careful consideration of multiplication factors a system employing one variable and one fixed oscillator allows all the signals required in the spectrometer to maintain phase coherence. It is demonstrated that the complete demodulator responds to pulses on a ns time scale and has a noise temperature of 737K.

The bis 1,4,7-trithiacyclononane (1,4,7-TTCN) complexes of iron, cobalt, nickel and copper are reported in this work. Their properties have been examined using computer-controlled electrochemical and spectroscopic techniques. These TTCN complexes form readily, are unusually symmetrical and support electron transfer reactions at the metal center. The cobalt(II) complex is octahedral, low spin and symmetrical. Four oxidation states of cobalt-TTCN complex are observed; two one-electron transfer processes are reversible. Copper (II) bis 1,4,7-TTCN is unusually symmetrical evidenced by both solid phase and ambient temperature aqueous phase electron paramagnetic resonance spectra. An unusually high redox potential for the copper complex indicates extraordinary stability of the Cu(I) oxidation state but evidently not at the expense of Cu(II) stability. The complex also has a high formation constant compared to other copper-thioether complexes. This unusual strength of thioether donor is attributed to ligand geometry. The 1,4,7-TTCN molecule is the only known cyclic polythioether to have all sulfur atoms endodentate. This structure contributes to thermodynamic stability of complexes as the ground state configuration of the free ligand is maintained in the complex.

Thesis (Ph. D.)--Ohio State University, 2005.
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Orientador: Pascoal José Giglio Pagliuso
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: A ideia de topologia na Física da Matéria da Condensada, apesar de ter surgido com o efeito Hall quântico inteiro, só voltou a ser explorada recentemente na busca de novas fases da matéria depois do surgimento dos Isolantes Topológicos (ITs) 2D. Após a previsão teórica, e a descoberta experimental, foi proposto que esta nova fase poderia ser generalizada para sistemas 3D, em que o volume do material seria isolante com estados metálicos de superfície que possuiriam canais de spin polarizados. Apesar de diversos experimentos e o surgimento de outras fases topológicas da matéria subsequentes, ainda há dúvidas sobre a natureza dos ITs 3D. Os efeitos topológicos mais claros ainda não foram observados de forma inequívoca e reprodutível experimentalmente e ainda seria de extrema valia encontrar técnicas experimentais que possam complementar os mais discutidos experimentos de ARPES. Nesta dissertação foram estudadas duas famílias distintas de materiais propostas como possíveis ITs 3D: os binários Bi2Se3 e Sb2Te3 e o half-Heusler YPdBi. Utilizando a técnica de auto-fluxo e a fusão estequiométrica, os sistemas foram sintetizados dopados com os terras-rara Gd3+, Nd3+ e Er3+ para realizar estudos de ressonância de spin eletrônico (RSE) e do papel dos efeitos de campo cristalino (CEF) - no caso do half-Heusler. Para o ternário YPdBi foram feitos dois estudos. Na família dos half-Heuslers, a ordem topológica surge da relação entre o acoplamento spin-órbita e a hibridização, que está ligada com a mudança do parâmetro de rede, então os efeitos de CEF poderiam estar refletindo a transição entre a trivialidade e a não-trivialidade. A partir das medidas de susceptibilidade magnética em função da temperatura das amostras dopadas com Nd3+ e Er3+ combinadas com os estudos de RSE, foi possível extrair os parâmetros de campo cristalino (CFP) de quarta e sexta ordem. Comparando esses dados com resultados anteriores para o material, supostamente, não-trivial YPtBi, observou-se uma mudança sistemática no sinal dos CFP. Resultados prévios para as amostras de YPtBi dopadas com Nd3+ mostram uma evolução não usual para uma forma de linha difusiva com a potência de micro-onda. Neste trabalho também foi realizado um estudo da forma de linha em função da potência. Apenas a ressonância do Nd3+ para os monocristais de 10% de Nd em YPdBi mostrou uma forma de linha difusiva que evolui com a potência da micro-onda. No caso dos binários Bi2Se3 e Sb2Te3, o objetivo era otimizar a rampa de tratamento térmico para obter monocristais melhores que poderiam permitir a observação de um espectro totalmente resolvido do Gd3+. Após mudanças no crescimento dos monocristais, o espectro totalmente resolvido foi obtido para as amostras de Bi2Se3. No caso do Sb2Te3 apenas uma linha central com a estrutura fina colapsada foi observada. Acompanhando o deslocamento g e a evolução da largura de linha dH da RSE do Gd3+ com a temperatura, o comportamento negativo do deslocamento g para toda a faixa de temperatura indica que elétrons do tipo p são os grandes responsáveis pela formação da superfície de Fermi residual destes sistemas. Um aumento no coeficiente angular de dH em função da temperatura, a taxa Korringa b, foi observado em baixas temperaturas, logo diferentes concentrações de Gd3+ foram utilizadas para estudar este comportamento. Novamente observou-se um comportamento anômalo em baixas temperaturas, o que poderia estar relacionado com a evolução dos CFP com a temperatura. Todos esses resultados foram discutidos levando-se em conta a possibilidade de existência de topologia não-trivial na estrutura eletrônica desses materiais, com foco particular na relação da interação spin-órbita e os efeitos de campo cristalino com a manifestação da topologia não trivial nesses sistemas
Abstract: The idea of topological systems in Condensed Matter Physics, although already explored in the Quantum Hall Effect, has recently become a topic of intense scientific investigation. In particular, great efforts have been dedicated to the search for new quantum phases since the proposal of the Topological Insulators (TIs) in 2D. After the theoretical prediction and the experimental discovery of the TIs in the 2D case, the existence of the Quantum Hall Spin Effect in 3D, 3D TIs, was proposed, where an insulator bulk and metallic surface states with spin polarized channels could be experimentally realized. Although many experiments have been performed, and some groups claimed the direct observation of such new topological phases, there is still a lot of controversy about the nature of the 3D TIs and about the actual microscopic origin of the metallic states on the surface of the studied materials. Other signatures of the topological phases have not been unambiguously and repeatedly measured yet and there is an obvious lack of a supplementary lab technique to be compared to the most used technique to probe these states, which is ARPES. In this work we have studied two different classes of 3D TIs: the binaries Bi2Se3 and Sb2Te3 and the half-Heusler YPdBi. We have been able to grow single crystals of these materials pure and rare-earth doped with Gd3+, Nd3+ and Er3+ using the self-flux technique and the stoichiometric melting. The aim was to use these crystals to study Electron Spin Resonance (ESR) as a potential probe to investigate the existence of the metallic surface states and to explore the possible of the crystalline electrical field (CEF) effects on the formation of the non-trivial electronic structure of these materials. Regarding the YPdBi, our ESR and magnetization studies have revealed that, in the half-Heusler family, the topological order emerges from the interplay between spin-orbit coupling and the hybridization, which is connected with the changes on the lattice parameter. Thus, the CEF effects could reflect the transition from trivial to nontrivial topology. From the magnetic susceptibility data as a function of temperature from the Nd3+ and Er3+ doped samples combined with the ESR studies, it was possible to extract the fourth and sixth order crystal field parameters (CFP). Comparing our data with the previous results from YPtBi, which is a putative non-trivial material, a systematic change in the sign of the CFP was observed. Previous results with the YPtBi Nd-doped samples show an unusual evolution of the Nd3+ ESR line to a diusive-like line shape as a function of the microwave power. In this work we have performed a similar study of the Nd3+ ESR line shape as a function of the microwave power. Only for the single crystal of 10% Nd in YPdBi resonance shows a diffusive-like line shape that evolves with the microwave power. In the case of the binaries Bi2Se3 e Sb2Te3, the aim of this work was to optimize the heat treatment used in previous works of our group to obtain better single crystals that could allow the observation of the full resolved spectra from Gd3+. After many changes in the single crystal growth method, we were able to observe fully resolved Gd3+ ESR spectra in the Bi2Se3 samples. Regarding the Sb2Te3 single crystals, only a single Gd3+ Dysonian ESR line was observed. Following the Gd3+ ESR dg and dH as a function of temperature, the observed negative behavior of dg, in the whole temperature range studied, indicates that p-type electrons are the main source for the formation of the small the Fermi surface of these materials. An increase of the angular coefficient of dH as a function of temperature, the Korringa rate b, at low temperatures was observed and different concentrations of Gd3+ were required to investigate this anomaly. Again this anomalous behavior at low temperatures was observed for the all Gd-doped samples, which could be related to an evolution of CFP with temperature. We discuss our results taking into account the existence of non-trivial topological states in our samples and the role of spin-orbit and CEF effects might have in the formation of such states
Mestrado
Física
Mestre em Física
132653/2015-0
CNPQ
CAPES
FAPESP

Une étude théorique ab initio des structures électroniques des molécules Diatomiques polaires BN, SiN et LaH dans la représentation 2s+1Λ(+/-)Ont été effectués par la méthode du champ auto-cohérent de l'espace Actif complet (CASSCF), suivie par l'interaction de la configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. L'ensemble de l'espace de configuration de CASSCF a été utilisé comme référence dans le calcul MRCI, qui a été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l'interface graphique Gabedit. Quarante-deux de plus bas états électroniques dans la représentation 2s+1Λ(+/-)au-dessous de 95000 cm-1 ont été étudiés de la molécule BN. Alors que vingt-huit états électroniques dans les représentations 2s+1Λ(+/-) jusqu'à 70000 cm-1 de la molécule de SiN ont été étudiés. D'autre part, les vingt-quatre bas états électroniques de LaH dans les représentations 2s+1Λ(+/-) au-dessous de 70000 cm-1 ont été étudiées par deux méthodes différentes et en prenant en considération l'effet des spin-orbite de la molécule LaH et nous avons observé la division énergétique des huit états électroniques. Les courbes d'énergie potentielle ont été construites avec la fréquence co-harmonique ωe, la distance internucléaire de l'équilibre re, les constantes de rotation Be. L'énergie électronique par rapport à l'état fondamentale Te a été calculé pour les états électroniques considérés comme des BN, SiN et la molécule LaH respectivement. En utilisant l'approche des fonctions canoniques, les valeurs propres Ev, les constantes rotationnelles Bv, la constante de distorsion centrifuge Dv et les abscisses des points de retournement Rmin and Rmax ont été calculés pour les états électroniques au niveau de vibration v=51 pour LaH molécule. Dix-huit et neuf états électroniques ont été étudiées pour la molécule BN et SiN respectivement. Pour LaH, vingt-trois états électroniques de la molécule LaH et l'effet de spin-orbite de molécule LaH sont donnés ici pour la première fois. La comparaison avec les données expérimentales et théoriques pour la plupart des constantes calculées démontre une très bonne précision. Enfin, ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules. Nos résultats ont été publiés dans le Canadian Journal of Chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer, nous avons deux autres articles en préparation à soumettre
In the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit

Les Moments Dipolaires Électriques (EDMs) de particules de spin 1/2 telles quele neutron constituent des sondes privilégiées de violation Charge-Parité (CP) au-delà du Modèle Standard, l’une des conditions requises pour expliquer l’asymétriebaryonique de l’Univers. L’expérience n2EDM, actuellement en cours d’assemblageau Paul Scherrer Institute en Suisse, est un des efforts majeurs de recherche de l’EDMdu neutron. Celle-ci consiste à soumettre des Neutrons Ultra-Froids (UCNs) polar-isés à des champs magnétiques et électriques appliqués parallèlement et de mesurerleur fréquence de précession. Cette expérience a pour objectif d’atteindre une sensi-bilité inégalée ∆dn ≤ 10−27 e cm, à condition de satisfaire des exigences très strictesen matière de maîtrise des erreurs statistiques et systématiques. Le travail présentédans ce manuscrit s’articule autour du contrôle d’effets systématiques induits parles non-uniformités du champ magnétique, à travers à la fois le calcul d’un de ceseffets et la caractérisation du milieu magnétique de l’expérience.La première partie de cette thèse justifie et présente n2EDM, en s’arrêtant surle thème de l’uniformité magnétique de l’expérience. Nous commençons par rap-peler les fondements théoriques sur lesquels reposent les recherches d’EDMs, quidécoulent d’observations cosmologiques selon lesquelles les interactions violant CPdoivent exister dans la nature et de l’incapacité du Modèle Standard (MS) à enfournir suffisamment. Nous présentons ensuite l’expérience n2EDM, en particulierla méthode de Ramsey sur laquelle celle-ci s’appuie pour déterminer la fréquencede précession des UCNs. Ceci nous permet enfin de détailler les exigences strictesd’uniformité que le champ magnétique interne doit satisfaire, ainsi que de justi-fier l’existence de contributions non uniformes en étudiant les symétries du champgénéré.La deuxième partie est axée autour du faux EDM, un effet systématique inquié-tant pour n2EDM qui naît de la combinaison d’un champ magnétique relativiste etde non-uniformités aléatoires. Nous proposons d’abord une nouvelle expression dufaux EDM dans le domaine fréquentiel via le théorème de Wiener-Khinchin, avant del’étendre à une approche récente permettant d’annuler cet effet en ajustant le champmagnétique à une valeur dite “magique”. Nous concluons grâce à notre calcul al-ternatif du champ magique et à son extension aux champs générés par des dipôlesmagnétiques qu’il est possible de supprimer le faux EDM d’au moins un ordre degrandeur en choisissant un champ magnétique de 10.5 μT.La troisième partie s’appuie sur une cartographie du champ magnétique pour es-timer et corriger les non-uniformités à l’origine d’effets indésirables tels que le fauxEDM. Après avoir établi l’exactitude de l’instrument de cartographie et maitrisé lesvariations du champ résiduel, nous montrons à travers l’analyse des données decartographie que l’environnement magnétique de n2EDM satisfait pleinement auxexigences statistiques et systématiques de l’expérience. Enfin, nous proposons et ap-pliquons une stratégie d’optimisation du champ afin de réduire davantage les non-uniformités résiduelles. Notre champ optimisé génère un faux EDM négligeable etprésente un niveau d’uniformité sans précédent, avec un écart quadratique moyensur la composante verticale σ(Bz) = 35 pT au sein du volume de précession
Electric Dipole Moments (EDMs) in spin 1/2 particles such as the neutron are highlysensitive probes for Charge-Parity (CP) violation Beyond the Standard Model (BSM),one of the requirements needed to fully explain the Baryon Asymmetry of the Uni-verse (BAU). The n2EDM experiment, currently in the commissioning phase at thePaul Scherrer Institute in Switzerland, constitutes a leading effort to search for theneutron EDM. It relies on the principle of submitting spin-polarized Ultra-Cold Neu-trons (UCNs) to parallel electric and magnetic fields and measuring their precessionfrequency. This experiment hopes to achieve a record sensitivity ∆dn ≤ 10−27 e cm,a goal which can only be reached by tackling statistical and systematical uncertain-ties affecting the measurement. The work we present here contributes to the controlof systematic errors generated by non-uniform magnetic fields, through the calcula-tion of a systematic effect and the precise characterization of the internal magneticenvironment.The first part of this thesis motivates and introduces the n2EDM experiment,particularly the theme of magnetic field uniformity. We begin with a review of thetheoretical grounds on which EDM experiments stand, which are prompted by cos-mological observations that CP-violating interactions must exist in nature, and bythe inability of the Standard Model (SM) of particle physics to provide enough ofthese. We then present the n2EDM experiment, which relies at its core on the Ram-sey method of separated rotating magnetic fields to determine the spin-precessionfrequency of UCNs. We finally give the stringent uniformity requirements that theinternal magnetic environment of n2EDM must satisfy, and justify the existence ofnon-uniform contributions by studying the symmetries of the generated field.The second part focuses on the so-called false EDM, a dire systematic effect inn2EDM arising from the unfortunate combination of a relativistic motional field andrandom non-uniformities. We first propose a new frequency-domain derivation ofthe false EDM via the Wiener-Khinchin theorem, before expanding on a recent ap-proach to cancel this effect by tuning the coil-generated field to a “magic value”.We conclude through our alternative calculation of the magic field, and its extensionto dipole-like magnetic contaminations, that it is possible to suppress the total falseEDM by at least one order of magnitude by setting the magnetic field to a value of10.5 μT.The third part relies on magnetic field mapping to estimate and correct non-uniformities responsible for undesirable effects such as the false EDM. After es-tablishing the accuracy of the mapping apparatus and taming unruly residual fieldpatterns, we show through an analysis of the mapping data that the n2EDM mag-netic environment fully satisfies the experiment’s statistical and systematical re-quirements. We finally propose and apply a field optimization strategy to suppressresidual non-uniformities even further. The optimized field generates a negligiblefalse EDM and boasts an unprecedented level of uniformity, with a root mean squaredeviation on the vertical field component σ(Bz) = 35 pT over the neutron’s preces-sion volume

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As membranas de troca aniônica são uma alternativa promissora para o desenvolvimento de eletrólitos mais eficientes para células a combustível alcalinas. Em geral, as membranas de troca aniônica são ionômeros capazes de conduzir íons hidroxila devido aos grupos quaternário de amônio e têm como característica elevado pH equivalente. Com o objetivo de desenvolver membranas aniônicas química e termicamente estáveis, com satisfatória condutividade iônica para aplicação em células a combustível alcalinas, as membranas aniônicas foram sintetizadas a partir de polímeros base de polietileno de baixa densidade (LDPE), polietileno de ultra alto peso molecular (PEUHMW), poli(etileno-co-tetrafluoroetileno) (PETFE) e poli(tetrafluoroetilleno-co-hexafluoroetileno) (PFEP) previamente irradiados nas fontes de radiação gama de 60Co ou com feixe de elétrons, para enxertia do monômero de estireno e funcionalizados com trimetilamina para incorporação dos grupos quaternário de amônio. As membranas resultantes foram caracterizadas por espectroscopia de ressonância paramagnética eletrônica (EPR), espectroscopia Raman, termogravimetria (TG), espectroscopia de impedância eletroquímica (EIS), além da determinação do grau de enxertia, capacidade de absorção de água por gravimetria e capacidade de troca iônica, por titulação. As membranas sintetizadas com os polímeros LDPE e UHMWPE pré-irradiados a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram resultados de condutividade iônica, quando na forma (OH-), de 29 mS.cm-1 e 14 mS.cm-1 a 65 °C, respectivamente. Os filmes de PFEP irradiados no processo simultâneo mostram níveis de enxertia insuficientes para a síntese de membranas aniônicas, necessitando maiores estudos para aperfeiçoar os processos de irradiação e enxertia. As membranas baseadas em PETFE, pré-irradiadas a 70 kGy com feixe de elétrons e armazenadas a baixa temperatura (-70 °C) por até 10 meses, mostraram maior condutividade iônica, quando na forma hidroxila (OH-), com valores de condutividade iônica entre 90 mS.cm-1 e 165 mS.cm-1 na faixa de temperatura entre 30 e 60 °C. Estes resultados mostraram que membranas de LDPE, UHMWPE e PETFE são eletrólitos promissores para a aplicação em células a combustível alcalinas.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Nesta dissertação é apresentado um estudo dos compostos Li1-3xMgFexPO4 através de Ressonância Magnética Nuclear (7Li e 31P), no intervalo de temperatura de 150 a 410 K. Estudos desses compostos através de técnicas de difração de elétrons e efeito Mossbauer confirmam que os íons Fe entram na rede cristalina na forma Fe3+, substituindo os íons Li+. O comportamento dos espectros de RMN, dos tempos de relaxação spin-rede e da susceptibilidade magnética dos núcleos 7Li e 31P em função da temperatura, em conjunto com medidas de condutividade iônica, indicam que, mesmo com a adição de impurezas Fe3+ na rede, os íons Li+ pouca mobilidade dentro do intervalo de temperatura utilizado.
This work reports a 7Li and 31P nuclear magnetic resonance study in the Li1-3xMgFexPO4 phases between 150 and 410 K. This study, complementary to those made using Mössbauer and magnetic neutron diffraction experiments, confirms that the Fe3+ ions enter as in the lattice, and that they enter substituting Li ions. The behavior of the 7Li e 31P nuclear magnetic resonance spectra, together with ionic conductivity measurements, show that no Li mobility occurs in temperature range studied even with the addition of the Fe impurity.

碩士
國立交通大學
電子物理系所
96
This thesis seeks after the manifestation of the electric-dipole-induced spin resonance (EDSR) in mesoscopics transport through a Rashba-type quantum channel. The EDSR con‾guration involves a static ‾eld along the channel and an ac electric ‾eld in parallel with the magnetic ‾eld. Within a time dependent perturbation that induces first sideband, we study the spin fipping in the transmitted wavefunctions. For the case when the incident energy falls within the Zeeman gap, and the sideband energies （ε±ω） outside of it, both the upper and lower sideband involves intraband (interband) transition which is nonspin (spin) fipping. Our major fnding is that the spin fipping component exhibits resonance characteristics when the sideband energy coincides with either the Zeeman gap edges or the subband bottom, when the density of state is large. Furthermore, the spin density oscillates in space according to the interference between the spin fipping and non-spin fipping comments. Additional beating features in the spin density spatial pro‾le is found to result from the interference between the spin density oscillations due to （ε+ω）and （ε-ω） sidebands. Our calculation has incorporated the effects of evanescent modes. We have performed a detail analyze on the evanescent modes. The longitudinal wavevector kx is found to be complex rather then pure imaginary.

It is of great importance to identify new sources of discrete symmetry violations because it can explain the baryon number asymmetry of our universe and also test the validity of various models beyond the standard model. Neutron Electric Dipole Moment (nEDM) and short-range force are such candidates for the new sources of P&T violations. A new generation nEDM experiment was proposed in USA in 2002, aiming at improving the current nEDM upperlimit by two orders of magnitude. Polarized 3He is crucial in this experiment and Duke is responsible for the 3He injection, measurements of 3He nuclear magnetic resonance (NMR) signal and some physics properties related to polarized 3He.

A Monte-Carlo simulation is used to simulate the entire 3He injection process in order to study whether polarized 3He can be successfully delivered to the measurement cell. Our simulation result shows that it is achievable to maintain more than 95% polarization after 3He atoms travel through very complicated paths in the presence of non-uniform magnetic fiels.

We also built an apparatus to demonstrate that the 3He precession signal can be measured under the nEDM experimental conditions using the Superconducting Quantum Interference Device (SQUID). Based on the measurement result in our lab, we project that the signal-to-noise ratio in the nEDM experiment will be at least 10.

During this SQUID test, two interesting phenomena were discovered. One is the pressure dependence of the T₁ of the polarized 3He which has never been reported before. The other is the discrepancy between the theoretically predicted T₂ and the experimentally measured T₂ of the 3He precession signal. To investigate these two interesting phenomena, two dedicated experiments were built, and two papers have been published in Physical Review A.

In addition to the nEDM experiment, polarized 3He is also used in the search for the exotic short-range force. The high pressure 3He cell used in this experiment has a very thin window (~250 μm) to maximize the effect from the force. We demonstrate that our new method could improve the current best experimental limit by two orders of magnitude. A rapid communication demonstrating the technique and the result was published in Physical Review D.

Dissertation

This thesis describes the physics, design, and construction of an experiment to measure the electric dipole moment (EDM) of the electron. In the experiment, laser-cooled Cs atoms will be held in an optical dipole force trap in the presence of applied electric and magnetic fields. The signature of an electron EDM is a first-order electric field shift of the Zeeman resonance frequency of the Cs ground state. We present an analysis of the systematic and statistical errors of this experiment, which shows that the experiment should have a sensitivity of the order of 10⁻²⁹ e-cm. We pay particular attention to potential light-shift induced errors and to magnetic field noise. We also present the design and experimental results for a cold Cs atom source, high voltage field plates, optical trapping field in a resonant build-up cavity, noval titanim ultrahigh vacuum system, and magnetic sheilding system. These results show that a measurement of the electron edm at the level of 10⁻²⁹ e-cm. should be feasible.
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