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Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-15T12:16:24Z No. of bitstreams: 1 arquivototal.pdf: 5169144 bytes, checksum: 66d534e3f0c0c59bf5d35a45290fa390 (MD5) / Made available in DSpace on 2016-03-15T12:16:24Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 5169144 bytes, checksum: 66d534e3f0c0c59bf5d35a45290fa390 (MD5) Previous issue date: 2015-02-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this thesis, we propose an experimental setup for the study of Landau quantization and associated effects in a two-dimensional ultracold atomic gas. Gauge fields can emerge in the equation of motion for the optically addressed ultracold atoms. To this end, spatially dependent dark states are necessary for the internal states of the atoms. A tripod level scheme yields two degenerate dark states which can leads to either an Abelian U(1) U(1) gauge field or a non-Abelian SU(2) gauge field. Using a suitable laser configuration, we obtain a uniform U(1) U(1) magnetic field which causes the atoms organize themselves in Landau levels. The strength of the effective magnetic field depends on the relative intensity of the lasers beams at the atomic cloud. We estimate the degeneracy of the energy levels for an atomic gas formed by atoms of 87Rb. In addition, we establish the experimental conditions to reach the lowest Landau level regime. In the zero-temperature limit, we realize the emergence of magnetic oscillations in the atomic energy and its derivative as function of the inverse of the effective magnetic field (de Haas van Alphen effect). The period of the de Haas van Alphen oscillation allow us to determine area of the Fermi circle for the atomic gas via an Onsager-like relation. We also show that detuning the a laser from the two-photon resonance we generate a parabolic scalar potential that laterally confines the atoms. As a consequence, the Landau levels degeneracy is removed, since the energy spectrum depends explicitly on the transverse atomic momentum. We show that the Landau levels presents a reminiscent degeneracy when the boundaries conditions are considered. The residual degeneracy occurs when different energy levels overlap. We map the residual degeneracy points as a function of the effective magnetic field. Finally, we present an experimental scheme for observing the spin Hall effect for ultracold atoms in a tripod configuration. / Nesta tese, propomos um arranjo experimental para o estudo da quantização de Landau e efeitos associados em um gás atômico ultrafrio bidimensional. Campos de calibre podem surgir na equação de movimento para átomos ultrafrios oticamente vestidos. Para que isto ocorra, estados escuros espacialmente dependentes são necessários a partir dos estados internos dos átomos. Átomos numa configuração de níveis de energia do tipo tripod produzem dois estados escuros degenerados, que podem levar a campos de calibre Abelianos U(1) U(1) ou não-Abelianos SU(2). Utilizando uma configuração adequada de lasers, mostramos que é possível se produzir um campo magnético sintético uniforme U(1) U(1) que atua nos átomos neutros fazendo-os se organizarem em níveis de Landau. A intensidade do campo efetivo depende da intensidade relativa dos feixes de luz na nuvem atômica. Estimamos a degenerescência dos níveis de energia para um gás atômico formado por átomos de 87Rb e estabelecemos as condições experimentais para que seja atingido o regime em que todos os átomos populam unicamente o nível de Landau menos energético. Considerando o limite de temperatura nula, verificamos o surgimento de oscilações magnéticas na energia e em sua derivada como uma função do inverso do campo magnético efetivo (efeito de Haas van Alphen). O período da oscilação magnética nos permite determinar a área do círculo de Fermi para o gás atômico através de uma expressão similar a de Onsager para sistemas eletrônicos. Mostramos também que dessintonizando um dos lasers em relação à ressonância de dois fótons geramos um potencial escalar parabólico que faz com os átomos sejam lateralmente confinados. Isto resulta na remoção da degenerescência dos níveis de Landau, uma vez que a energia depende explicitamente do momento atômico transverso. Demonstramos que, aplicando condições periódicas de contorno ao sistema, temos o surgimento de uma degenerescência residual. A degenerescência remanescente ocorre quando diferentes níveis de energia se superpõem. Mapeamos os pontos de degenerescência como uma função do campo magnético efetivo. Por fim, apresentamos um esquema experimental para a observação do efeito spin Hall para átomos ultrafrios em uma configuração tripod.

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This thesis focuses on the work of the Čapeks Brothers and monitors their premonition of a coming destruction, the World War II. It consists of two parts theoretical and practical. The practical part presents poster set freely interpreting a Hugo Haas film The White Disease.

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Heavy fermion metals often exhibit novel electronic states at low temperatures, due to competing interactions and energy scales. In order to characterize these states, precise determination of material electronic properties, such as the Fermi surface topology, is necessary. Magnetic field is a particularly powerful tool, since it can be used as both a tuning parameter and probe of the fundamental physics of heavy fermion compounds. In CePb3, I measured magnetoresistance and torque for 23 mK ≤ T ≤ 400 mK, 0 T ≤ H ≤ 18 T, and magnetic field rotated between the (100), (110), and (111) directions. For H||(111), my magnetoresistance results show a decreasing Fermi liquid temperature range near Hc, and a T^2 coefficient that diverges as A(H) ∝ |H −Hc|^−α, with Hc ~ 6 T and α ~ 1. The torque exhibits a complicated dependence on magnetic field strength and angle. By comparison to numerical spin models, I find that the “spin-flop” scenario previously thought to describe the physics of CePb3 does not provide a good explanation of the experimental results. Using novel data acquisition software that exceeds the capabilities of a traditional measurement set-up, I measured de Haas–van Alphen oscillations in YbRh2Si2 for 30 mK ≤ T ≤ 600 mK, 8 T ≤ H ≤ 16 T, and magnetic field rotated between the (100), (110), and (001) directions. The measured frequencies smoothly increase as the field is decreased through H0 ≈ 10 T. I compared my measurements to 4f-itinerant and 4f-localized electronic structure calculations, using a new algorithm for extracting quantum oscillation information from calculated band energies, and conclude that the Yb 4f quasi-hole remains itinerant over the entire measured field range, with the behaviour at H0 caused by a Fermi surface Lifshitz transition. My measurements are the first to directly track the Fermi surface of YbRh2Si2 across this field range, and rule out the 4f localization transition/crossover that was previously proposed to occur at H0.

This thesis describes investigations into the properties of -phase BEDT-TTF charge transfer salts. Charge transfer salts are mainly studied as they are very useful test beds for fundamental physics due to the tuneability of their proper- ties and ground states. The effects of temperature and pressure on such systems have been studied, as these allow access to a wide range of different states and properties. Transport properties of these systems have been studied to obtain information about the Fermi surface and effective mass, and the effect of deuter- ation and also change of pressure media will be discussed. The interaction of infrared radiation with these systems has also been investigated and simultaneous pressure and temperature measurements will be presented, something not greatly studied due to the large technical challenges. The techniques and approaches for overcoming these are also discussed. Chapter 1 provides an introduction to the organic materials themselves with particular emphasis on the actual compounds studied. Chapter 2 provides the necessary theoretical background for studying organic charge transfer salts using magnetic quantum oscillations and their infrared re- ectivity. Chapter 3 covers the experimental techniques and also discusses some of the challenges encountered and their solutions to aid others working in this area. Chapter 4 describes an investigation into the transport properties of - (ET)2Cu(SCN)2 by studying Shubnikov-de Haas oscillations using both deuter- ated and normal samples and using two different pressure media, and comparing it to work done using a third. Chapter 5 presents an investigation into the pressure dependence of selected phonon modes in -(ET)2Cu(SCN)2 using infrared radiation on a deuterated sam- ple. Chapter 6 presents what is believed to be the first pressure and temperature dependent infrared study of an organic molecular material. In this case the or- ganic molecular material is d8--(ET)2Cu[N(CN)2]Br, but the techniques should be readily transferable to other materials.

Heavy fermion metals often exhibit novel electronic states at low temperatures, due to competing interactions and energy scales. In order to characterize these states, precise determination of material electronic properties, such as the Fermi surface topology, is necessary. Magnetic field is a particularly powerful tool, since it can be used as both a tuning parameter and probe of the fundamental physics of heavy fermion compounds. In CePb3, I measured magnetoresistance and torque for 23 mK ≤ T ≤ 400 mK, 0 T ≤ H ≤ 18 T, and magnetic field rotated between the (100), (110), and (111) directions. For H||(111), my magnetoresistance results show a decreasing Fermi liquid temperature range near Hc, and a T^2 coefficient that diverges as A(H) ∝ |H −Hc|^−α, with Hc ~ 6 T and α ~ 1. The torque exhibits a complicated dependence on magnetic field strength and angle. By comparison to numerical spin models, I find that the “spin-flop” scenario previously thought to describe the physics of CePb3 does not provide a good explanation of the experimental results. Using novel data acquisition software that exceeds the capabilities of a traditional measurement set-up, I measured de Haas–van Alphen oscillations in YbRh2Si2 for 30 mK ≤ T ≤ 600 mK, 8 T ≤ H ≤ 16 T, and magnetic field rotated between the (100), (110), and (001) directions. The measured frequencies smoothly increase as the field is decreased through H0 ≈ 10 T. I compared my measurements to 4f-itinerant and 4f-localized electronic structure calculations, using a new algorithm for extracting quantum oscillation information from calculated band energies, and conclude that the Yb 4f quasi-hole remains itinerant over the entire measured field range, with the behaviour at H0 caused by a Fermi surface Lifshitz transition. My measurements are the first to directly track the Fermi surface of YbRh2Si2 across this field range, and rule out the 4f localization transition/crossover that was previously proposed to occur at H0.

La création artistique autochtone est indissociable des luttes politiques. Dans un contexte colonial, les modes d’être, d’agir et de penser Autochtones sont profondément affectés. L’art est une arme puissante dans cette lutte pour la décolonisation. Cette étude s’intéressera ainsi au potentiel de transformation et de décolonisation de la création artistique autochtone, à travers la pratique artistique de l’artiste Algonquine Nadia Myre. Plusieurs de ses œuvres adressent la mixité identitaire et la violence coloniale subie par les Autochtones. Indian Act (fig.1) dénonce, à l’aide d’une réécriture perlée traditionnelle et participative, un texte de loi colonial qui a conduit à une injustice épistémique profonde. Pour adresser ces problématiques, nous nous ancrerons sur un objet particulier, le wampum. Dans cette recherche, nous le considérerons comme un vecteur de résurgence et de décolonisation profondes. La position socio-politique ancienne et contemporaine essentielle du wampum en fait un support didactique privilégié de résurgence. Grâce à l’utilisation du motif du wampum dans la pratique artistique de Nadia Myre, nous pourrons cheminer à travers ces luttes et comprendre comment les artistes Autochtones les engagent. Le wampum sera présenté comme une rhétorique discursive, matérielle et immatérielle, un hypertexte, un hyperlien (Haas 2007) entre tradition et modernité, oralité et écriture, qui sera supportée par la théorie de l’intermédialité. Jacques Derrida et la Déconstruction seront également convoqués pour examiner le travail de réécriture effectué par Myre dans Indian Act. Il s’agira également de comprendre comment la proposition participative de Nadia Myre pourrait permettre un engagement allochtone vers une justice épistémique décoloniale. / Aboriginal artistic creation is inseparable from political struggles. In a colonial context, Aboriginal ways of being, acting and thinking are deeply affected. Art is a powerful weapon in this struggle for decolonization. This study will therefore focus on the transformative and decolonizing potential of Aboriginal artistic creation through the artistic practice of Algonquin artist Nadia Myre. Several of her works address the mixed identity and colonial violence suffered by Aboriginal people. Indian Act (fig.1) denounces, through a traditional and participatory beaded rewriting, a colonial law that has led to a profound epistemic injustice. To address these issues, we will focus on a specific object, the wampum. In this research, we will consider it as a vector of deep resurgence and decolonization. The essential ancient and contemporary socio-political position of wampum makes it a privileged didactic support of resurgence. Through the use of the wampum motif in Nadia Myre's artistic practice, we will be able to walk through these struggles and understand how Aboriginal artists engage them. Wampum will be presented as a discursive rhetoric, material and immaterial, a hypertext, a hyperlink (Haas 2007) between tradition and modernity, orality and writing, which will be supported by the theory of intermediality. Jacques Derrida and the Deconstruction will also be convened to examine the rewriting work done by Myre in Indian Act. It will also be a question of understanding how Nadia Myre's participatory proposal could enable an allochtonous engagement towards decolonial epistemic justice.