Nematic and supernematic phases in Kagome quantum antiferromagnets under a magnetic field

Optimizing translationally invariant infinite-Projected Entangled Pair States (iPEPS), we investigate the spin-2 Affleck-Kennedy-Lieb-Tasaki (AKLT) and spin-1 Heisenberg models on the Kagome lattice as a function of magnetic field. We found that the magnetization curves offer a wide variety of compressible and incompressible phases. Incompressible nematic phases breaking the lattice $C_3$ rotation -- for which we propose simple qualitative pictures -- give rise to magnetization plateaux at reduced magnetization $m_z=5/6$ and $m_z=1/3$ for spin-2 and spin-1, respectively, in addition to the $m_z=0$ plateaux characteristic of zero-field gapped spin liquids. Moving away from the plateaux we observe a rich variety of compressible superfluid nematic -- named "supernematic" -- phases breaking spontaneously both point group and spin-U(1) symmetries, as well as a superfluid phase preserving lattice symmetries. We also identify the nature -- continuous or first-order -- of the various phase transitions. Possible connections to experimental spin-1 systems are discussed.Comment: 5 pages + supplemental material (6 pages

Spin-S Kagome quantum antiferromagnets in a field with tensor networks

Spin-$S$ Heisenberg quantum antiferromagnets on the Kagome lattice offer, when placed in a magnetic field, a fantastic playground to observe exotic phases of matter with (magnetic analogs of) superfluid, charge, bond or nematic orders, or a coexistence of several of the latter. In this context, we have obtained the (zero temperature) phase diagrams up to $S=2$ directly in the thermodynamic limit thanks to infinite Projected Entangled Pair States (iPEPS), a tensor network numerical tool. We find incompressible phases characterized by a magnetization plateau vs field and stabilized by spontaneous breaking of point group or lattice translation symmetry(ies). The nature of such phases may be semi-classical, as the plateaus at $\frac{1}{3}$th, $(1-\frac{2}{9S})$th and $(1-\frac{1}{9S})$th of the saturated magnetization (the latter followed by a macroscopic magnetization jump), or fully quantum as the spin-$\frac{1}{2}$ $\frac{1}{9}$-plateau exhibiting coexistence of charge and bond orders. Upon restoration of the spin rotation $U(1)$ symmetry a finite compressibility appears, although lattice symmetry breaking persists. For integer spin values we also identify spin gapped phases at low enough field, such as the $S=2$ (topologically trivial) spin liquid with no symmetry breaking, neither spin nor lattice.Comment: 5 pages, 3 figures, 1 table + supplemental materia

Systèmes de spins quantiques frustrés sous champ magnétique étudiés par méthodes Tensor Network

Magnetic frustration is a physical property that is the topic of numerous studies. It occurs when the system geometry does not permit simultaneous minimisation of local energies, which leads to a macroscopic degeneracy. Present in nature through various minerals, including the famous herbertsmithite, the antiferromagnetic kagome lattice is a perfect example of two-dimensional frustrated system. When an external magnetic field tending to polarised the material is added to this property, the competition of these two phenomenas give rise to exotic magnetisation processes, such as magnetisation plateaux for which the magnetic susceptibility is zero. We studied the kagome lattice with the AKLT Hamiltonian of spin 2 and the Heisenberg Hamiltonian for spin 1/2, 1, 3/2 and 2 in a magnetic field. This work was performed using numerical methods called Tensor Network methods. First developed in the context of quantum information theory, these methods, based on the principle of entanglement, were quickly used in condensed matter. They allowed the study of two-dimensional frustrated systems previously limited to the already known numerical methods such a Monte Carlo or DMRG methods. We were able to produce rich phase diagrams for all models listed, depending on the magnetic field.La frustration magnétique est une propriété physique faisant l'objet de très nombreuses études. Elle intervient lorsque la géométrie du système ne permet pas la minimisation simultanée des énergies locales, menant alors à une dégénérescence macroscopique. Présent dans la nature au travers de différents minéraux, dont la célèbre herbertsmithite, le réseau kagomé antiferromagnétique est un parfait exemple de système bidimensionnel frustré. Lorsqu'à cette propriété s'ajoute un champ magnétique extérieur tendant à polariser le matériau, la compétition de ces deux phénomènes donne naissance à des processus d'aimantation exotiques, tels que les plateaux d'aimantation pour lesquels la susceptibilité magnétique est nulle. Nous avons étudié le réseau kagomé avec le hamiltonien AKLT de spin 2 et le hamiltonien de Heisenberg pour les spins 1/2, 1, 3/2 et 2 sous champ magnétique. Ce travail a été effectué en utilisant des méthodes numériques appelées méthodes Tensor Network. Tout d'abord développées dans le cadre de la théorie quantique de l'information, ces méthodes, basées sur le principe d'intrication, ont très vite été utilisées en matière condensée. Elles ont permis l'étude de systèmes bidimensionnels frustrés, jusqu'alors limitée aux méthodes numériques déjà connus telles que les méthodes Monte Carlo ou encore DMRG. Nous avons été en mesure de produire les diagrammes de phases, d'une grande richesse, pour tous les modèles cités, en fonction du champ magnétique

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Altimetry for the future: building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion

Troubles du comportement sexuel et syndrome de Klinefelter (revue de la littérature et discussion à partir de deux cas cliniques)

Le phénomène de l'agression sexuelle est devenu une préoccupation majeure de notre société. Les médecins et en particulier les psychiatres ont été interpellés pour la prise en charge des troubles du comportement sexuel. Dans le cadre des hypothèses biologiques des perversions, nous nous sommes intéressés plus particulièrement au syndrome de Klinefelter; ce syndrome constitue la forme la plus commune des hypogonadismes masculins. Après avoir décrit ce syndrome et passé en revue les différents aspects actuels des troubles du comportement sexuel, nous avons étudié, à l'aide d'une revue de la littérature et de l'analyse de deux cas cliniques, l'éventuelle intrication entre cette anomalie chromosomique et l'émergence d'un comportement sexuel déviant. Même si le syndrome de Klinefelter présente de nombreux facteurs de risque au développement d'un trouble du comportement sexuel, cette anomalie chromosomique ne peut actuellement être assimilée à une prédisposition aux perversions.ROUEN-BU Médecine-Pharmacie (765402102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

Spin-1/2 kagome XXZ model in a field: Competition between lattice nematic and solid orders

International audienc

Ice Sheet Topography from a New CryoSat-2 SARIn Processing Chain, and Assessment by Comparison to ICESat-2 over Antarctica

In this study, we present a new level-2 processing chain dedicated to the CryoSat-2 Synthetic Aperture Radar Interferometric (SARIn) measurements acquired over ice sheets. Compared to the ESA ground segment processor, it includes revised methods to detect waveform leading edges and perform retracking at the Point of Closest Approach (POCA). CryoSat-2 SARIn mode surface height measurements retrieved from the newly developed processing chain are compared to ICESat-2 surface height measurements extracted from the ATL06 product. About 250,000 space–time nearly coincident observations are identified and examined over the Antarctic ice sheet, and over a one-year period. On average, the median elevation bias between both missions is about −18 cm, with CryoSat-2 underestimating the surface topography compared to ICESat-2. The Median Absolute Deviation (MAD) between CryoSat-2 and ICESat-2 elevation estimates is 46.5 cm. These performances were compared to those obtained with CryoSat-2 SARIn mode elevations from the ESA PDGS level-2 products (ICE Baseline-D processor). The MAD between CryoSat-2 and ICESat-2 elevation estimates is significantly reduced with the new processing developed, by about 42%. The improvement is more substantial over areas closer to the coast, where the topography is more complex and surface slope increases. In terms of perspectives, the impacts of surface roughness and volume scattering on the SARIn mode waveforms have to be further investigated. This is crucial to understand geographical variations of the elevation bias between CryoSat-2 and ICESat-2 and continue enhancing the SARIn mode level-2 processing

Ice Sheet Topography from a New CryoSat-2 SARIn Processing Chain, and Assessment by Comparison to ICESat-2 over Antarctica

In this study, we present a new level-2 processing chain dedicated to the CryoSat-2 Synthetic Aperture Radar Interferometric (SARIn) measurements acquired over ice sheets. Compared to the ESA ground segment processor, it includes revised methods to detect waveform leading edges and perform retracking at the Point of Closest Approach (POCA). CryoSat-2 SARIn mode surface height measurements retrieved from the newly developed processing chain are compared to ICESat-2 surface height measurements extracted from the ATL06 product. About 250,000 space–time nearly coincident observations are identified and examined over the Antarctic ice sheet, and over a one-year period. On average, the median elevation bias between both missions is about −18 cm, with CryoSat-2 underestimating the surface topography compared to ICESat-2. The Median Absolute Deviation (MAD) between CryoSat-2 and ICESat-2 elevation estimates is 46.5 cm. These performances were compared to those obtained with CryoSat-2 SARIn mode elevations from the ESA PDGS level-2 products (ICE Baseline-D processor). The MAD between CryoSat-2 and ICESat-2 elevation estimates is significantly reduced with the new processing developed, by about 42%. The improvement is more substantial over areas closer to the coast, where the topography is more complex and surface slope increases. In terms of perspectives, the impacts of surface roughness and volume scattering on the SARIn mode waveforms have to be further investigated. This is crucial to understand geographical variations of the elevation bias between CryoSat-2 and ICESat-2 and continue enhancing the SARIn mode level-2 processing