Intertwined ordered states in NdxCe1−xCoIn5

The physics of a many-body system of strongly interacting particles defies simple extrapolation of the behavior of individual particles constructed ab-initio. Rather, interactions lead to complex phenomena and stabilize ground states with deeply intertwined degrees of freedom. As a result, novel collective phenomena emerge that are interesting from both fundamental and technological perspectives, as shown in this thesis. Here, the complex phenomena in Nd$_x$Ce$_{1-x}$CoIn$_5$ are discussed with a focus on the interplay between superconductivity and magnetism. Two main techniques were used: neutron diffraction and ultrasound spectroscopy. It is shown that concentrations as low as 2$\%$ of local-moment Nd ions are sufficient to induce a spin density wave at zero field. The application of magnetic fields transverse to the moment direction suppresses the magnetic order at low fields, but at higher fields, a spin density wave emerges with the same magnetic structure at the Q-phase. These ground states, which have identical symmetry, show completely different interactions between superconductivity and magnetism. While superconductivity is necessary for magnetism at the Q-phase, in the low-field phase, a competing interplay between these orders is found. A detailed investigation of the low field spin density wave revealed a domain selection in the normal state. This study lead to the discovery of a new spintronic phenomenon that allows switching of antiferromagnetic domains without a Zeeman component. Our findings could also inspire studies on other materials and possibly provide a new route to control antiferromagnetic domains. In this work, a new, flexible, digital ultrasound setup was developed. The results obtained with it show that the nature of the high-field state is deeply intertwined with the d-wave condensate. The Q-phase quantum critical field exhibits a fourfold rotational symmetry in the basal plane. The out-of-plane angular dependence of the upper critical field is characterized within a Pauli limiting model. The Q-phase critical field, however, cannot be characterized as such. Instead, our data is well described by assuming a connection with the high field state observed for $\boldsymbol{H} \parallel [0 0 1]$. Furthermore, our measurements of shear elastic modes provide evidence for vortices that are well separated along the c-axis but show an interconnection within basal plane. This interconnection could be a necessary condition for long-range ordering in the Q-phase. Although our investigations focused on the physics of CeCoIn$_5$, our results are relevant in many different research areas

Eclogitic metatrondhjemites from metaophiolites of the Western Alps

In the Urtier valley (southern Aosta Valley, Italy), the Piemonte metaophiolites mainly consist of serpentinized peridotites including pods and boudinaged layers of Fe-metagabbro and trondhjemite transposed in the main eclogitic foliation. The contact between serpentinized peridotites and Fe-metagabbro/trondhjemite is locally lined by chloriteschist and rodingite. The high pressure parageneses in the Fe-metagabbro are omphacite-garnet-rutile-glaucophane-phengite, and in the metatrondhjemite plagioclase-quartz-phengite-clinozoisite-epidote-garnet, respectively. Bulk-rock major and trace elements in addition to O isotope analyses were performed in both rock types. Fe-metagabbros are characterized by MgO wt% ranging between 6.11 and 9.63%, EREE= 20-101 ppm, (La/Yb)N = 0.22-0.91; trondhjemites have SiO2 43%, Al2O3 ranging between 21 and 24%, CaO ranging between 17 and 20%, EREE = 172 - 272 ppm, (La/Yb)N ranging between 7.78 and 13.70. The 18O is 5.9 per-mil in a Fe-metagabbro sample and 7.4 per-mil in a trondhjemite sample, suggesting that these rocks have been affected by a weak oceanic low temperature alteration. The high CaO content may indicate a metasomatic process which could have occurred during the oceanic stage or at high pressure conditions

Record of Jurassic mass transport processes through the orogenic cycle: Understanding chaotic rock units in the high-pressure Zermatt-Saas ophiolite (Western Alps)

The eclogite facies Zermatt-Saas ophiolite in the Western Alps includes a composite chaotic unit exposed in the Lake Miserin area, in the southern Aosta Valley region. The chaotic unit is characterized by a block-in-matrix texture consisting of ultramafic clasts and blocks embedded within a carbonate matrix. This unit overlies massive serpentinite and ophicarbonate rocks and is unconformably overlain by layered calcschist. Despite the effects of subduction and collision-related deformation and metamorphism, the internal stratigraphy and architecture of the chaotic unit are recognizable and are attributed to different types of mass transport processes in the Jurassic Ligurian-Piedmont Ocean. This finding represents an exceptional record of the preorogenic history of the Alpine ophiolites, marked by different pulses of extensional tectonics responsible for the rough seafloor topography characterized by structural highs exposed to submarine erosion. The Jurassic tectonostratigraphic setting envisioned is comparable to that observed in present-day magma-poor slow- and ultraslow-spreading ridges, characterized by mantle exposure along fault scarps that trigger mass transport deposits and turbiditic sedimentation. Our preorogenic reconstruction is significant in an eclogitized collisional orogenic belt in which chaotic rock units may be confused with the exclusive product of subduction-related tectonics, thus obscuring the record of an important preorogenic history. \ua9 2017 Geological Society of America

Permeability Structure of the Lava-Dike Transition of 15 My Old Oceanic Crust Formed at the East Pacific Rise

The permeability structure of oceanic crust controls both the spatial and temporal extent of hydrothermal circulation, but the detailed geometry of fractures in seafloor rocks is not well known. We apply an equivalent channel model to veins, joints, faults, and breccias preserved in recovered cores from ODP-IODP Hole 1256D to calculate paleo-permeability. In the ~250 m transition between dikes and lavas, paleo-permeability is 10-13~10-14 m2 with narrow zones of >10-9 m2 that presumably act as conduits for the largest volume of fluids. Most of these high permeability zones are oriented vertically as a result of diking events into a significant thickness of lavas outside of the neovolcanic zone. After an increase in permeability due to off-axis diking events, fluid temperatures drop, pathways are sealed, and the permeability of the upper oceanic crust drops significantly

The St. Marcel Valley, Western Alps: metaophiolites, metasedimentary sequence and tectonic setting

In the Southern Aosta Valley, the St. Marcel Valley metaophiolites consist of mainly metavolcanics and their sedimentary cover metamorphosed under HP subduction-related metamorphism. A detailed geological map carried out in the St. Marcel Valley reveals that the metasedimentary cover, although transposed by the Alpine tectonics, is essentially made of three main terms, that are Mn-rich metaquartzites, marble, and calcschists. The metasedimentary sequence is quite comparable with the unmetamorphosed sequence made of radiolarian cherts, Calpionella limestones and Palombini shales covering the Ligurian ophiolites. The St. Marcel Valley metaophiolites represent the upper crustal section of the Mesozoic Tethyan ocean and its pelagic sedimentary cover, overthrusting the serpentinite unit of the Mount Avic, to the East. Within the Piemonte nappe stack, the St.Marcel metaophiolites are located at the higher structural level

Optimization of radiation hardness and charge collection of edgeless silicon pixel sensors for photon science

Recent progress in active-edge technology of silicon sensors enables the development of large-area tiled silicon pixel detectors with small dead space between modules by utilizing edgeless sensors. Such technology has been proven in successful productions of ATLAS and Medipix-based silicon pixel sensors by a few foundries. However, the drawbacks of edgeless sensors are poor radiation hardness for ionizing radiation and non-uniform charge collection by edge pixels. In this work, the radiation hardness of edgeless sensors with different polarities has been investigated using Synopsys TCAD with X-ray radiation-damage parameters implemented. Results show that if no conventional guard ring is present, none of the current designs are able to achieve a high breakdown voltage (typically < 30 V) after irradiation to a dose of ~10 MGy. In addition, a charge-collection model has been developed and was used to calculate the charges collected by the edge pixels of edgeless sensors when illuminated with X-rays. The model takes into account the electric field distribution inside the pixel sensor, the absorption of X-rays, drift and diffusion of electrons and holes, charge sharing effect, and threshold settings in ASICs. It is found that the non-uniform charge collection of edge pixels is caused by the strong bending of electric field and the non-uniformity depends on bias voltage, sensor thickness and distance from active edge to the last pixel ("edge space"). In particular, the last few pixels close to the active edge of the sensor are not sensitive to low-energy X-rays (< 10 keV) especially for sensors with thicker Si and smaller edge space. The results from the model calculation have been compared to measurements and good agreement was obtained. The model has been used to optimize the edge design.Comment: 12 pages, 8 figure

Phylogenetic Approach to the Study of Triatomines (Triatominae, Heteroptera) = Abordagem filogenética em Triatomíneos (Triatominae, Heteroptera)

Triatomines are insects belonging to the Hemiptera order, Heteroptera suborder, Reduviidae family and Triatominae subfamily. All members of this subfamily are hematophagous. Triatomines evolved from Reduviidae predators and they are probably polyphyletic in origin. The combination of anatomical, physiological and ethological factors observed in this group, as well as the plesiomorphic and apomorphic characters that differentiate the five tribes and fourteen triatomine genera reinforce the polyphiletic hypotesis. However if we consider the five groups of triatomines, the Rhodniini, Cavernicolini, Bolboderini, Linshcosteini and Alberproseniini tribes constitute monophyletic groups, while the Triatomini tribe is considered polyphyletic. The New World is the center of triatomine diversity and seems to be the point of group origin. Of approximately 137 triatomine species, 105 are only found in the Americas. It is now considered that triatomines represent a polyphyletic group defined according to their convergent apomorphic hematophagous characters, which have appeared several times in Reduviidae. This study revises the phylogeny of these vectors of Chagas’ disease, covering such topics as the origin of hematophagy in triatomines and ancestral proposal for the group. Resumo Os triatomíneos são insetos pertencentes à ordem Hemiptera, subordem Heteroptera, família Reduviidae e subfamília Triatominae. Todos os membros desta subfamília são hematófagos. Os triatomíneos surgiram a partir de reduvídeos predadores e provavelmente têm origem polifilética. A combinação dos fatores anatômicos, fisiológicos e etológicos presentes no grupo, bem como os caracteres plésio e apomórficos que diferenciam as cinco tribos e os quatorze gêneros de triatomíneos reforçam a hipótese polifilética. As tribos Rhodniini, Cavernicolini, Bolboderini, Linshcosteini e Alberproseniini constituem grupos monofiléticos, per si, enquanto a tribo Triatomini é considerada polifilética. O Novo Mundo é claramente o centro de diversidade dos triatomíneos e possivelmente é a região de sua origem. Entre as aproximadamente 129 espécies desses insetos, 105 ocorrem somente nas Américas. Atualmente, os triatomíneos são considerados um grupo polifilético, definido com base em seus caracteres apomórficos convergentes relacionados à hematofagia. Acredita-se que este hábito alimentar tenha surgido várias vezes nos Reduviidae durante sua evolução. O presente trabalho faz uma revisão sobre a filogenia destes vetores da Doença de Chagas, aborda tópicos como a origem da hematofagia nos triatomíneos e ancestralidade proposta para o grupo