Résumé: Review article (42 pages) In this work, I shall summarize different phenomenological approaches of vortex trapping as well in conventional superconductors that serve as a basis for experimental fact interpretations in new superconductors as in massive and nanometric high critical temperature superconductors, and I shall present our experimental studies on vortex trapping in single crystals of La1.85Sr0.15CuO and YBa2Cu3O7-δ but also in nanoparticles of YBa2Cu3O7-δ. Particular attention should be paid to the study of high-TC superconducting nanoparticles of YBa2Cu3O7-δ system doped with magnetic nanoparticles of Y3Fe5O12. The reduction in the size of grains of these two compounds by mechanical grinding led to the size disparities of these grains, confirmed by an analysis by means of an atomic force microscope. These disparities are inherent in mechanical grinding. The average sizes of the obtained nanoparticles were estimated to be in the range of 80 nm by means of XRD reflection using the Scherrer equation. The nanometric size of the obtained grains revealed new phenomena considered in the past as contradictory like the coexistence of ferromagnetism and superconductivity and the trapping of vortices by spins which were studied herein detail and allowed us highlighting this coexistence and interpreting the variations in field and temperature of the critical current density JC in this system.

Résumé: Magnetic measurements have been reported in nanosized YBa2Cu3O 7-δ (YBCO) cylindrical tablets doped with different proportions of Y3Fe5O12 (YIG) nanoparticles. X-ray diffraction and magnetization measurements have been achieved to characterize samples and study the influence of temperature T, applied field H, and added YIG on the intergranular critical current JC. The field has been applied perpendicular to the tablet. Temperature exponential decay of JC in YBCO nanoparticles has been observed and analyzed in the collective and correlated model framework. A two-current model has been proposed: the low-T region behavior has been attributed to the trapping effectiveness of ferromagnetic and superconducting nanoarea interfaces. In the high-T region, there are many ferromagnetic traps to ensnare a very small number of vortices leading to a flexing of JC decrease vs. T and to very low values of JC. Field dependence of JC of many tablets of YBCO with different YIG quantities has shown an optimum enhancement of JC for 0.5% of YIG in weight.

Résumé: A new automatic C/C++ program which generates all linked and essentially distinct vacuum Hugenholtz-type diagrams of many-body perturbation series up to arbitrary order is presented. The output results are shown as lists of integers which present the sites of suitable vertex of each diagram with its symmetry factor. The analysis results up to 10-order are displayed.

Résumé: In order to interpret the low-H peak and the particular form of M(H) curves of pure YBa2Cu3O7-δ (YBCO) nanoparticles, many pellets of YBa2Cu3O7-δ/Y3Fe5O12 (YBCO/YIG) with different proportions of added YIG were prepared by pressing nanoparticles into disks of 5 mm diameter and 0.5 mm thickness and high temperature sintering. The crystal structure and phase composition of YBa2Cu3O7-δ and Y3Fe5O12 were characterized by X-ray diffraction (XRD) with CoKα radiation. Magnetization measurements vs. temperature T and applied field H were performed with a conventional magnetometer in the temperature range 4.2–110 K and in magnetic fields up to 10 T. The field was applied parallel to the pellet axis. Our results reveal that the application of a strong field leads to a phase transition: for H less than a threshold field H*, the superconducting nano-domains areprevalent in the sample. When the field increases beyond H*, superconducting nano-domains spins line up along the applied field direction to create a ferromagnetic phase. Phase diagrams are proposed. Field dependence of the critical current JC in YBCO pellet has revealed the existence of two pinning mechanisms: a pinning at low fields and a pinning at higher fields.

Résumé: This book provides a simple and well-structured course followed by an innovative collection of exercises and solutions that will enrich a wide range of courses as part of the undergraduate physics curriculum. It will also be useful for first-year graduate students who are preparing for their qualifying exams. The book is divided into four main themes at the boundary of classical and modern physics: atomic physics, matter-radiation interaction, blackbody radiation, and thermodynamics. Each chapter starts with a thorough and well-illustrated review of the core material, followed by plenty of original exercises that progress in difficulty, replete with clear, step-by-step solutions. This book will be invaluable for undergraduate course instructors who are looking for a source of original exercises to enhance their classes, while students that want to hone their skills will encounter challenging and stimulating problems.