Type-II Superconductivity in Ternary Zirconium Pnictide Chalcogenide Single Crystals

Layered Pnictides are proven to be a great reservoir for superconductors in the past and ternary zirconium pnictide chalcogenides of ZrXY-type (X = P, As; Y = S, Se) might be a platform for new superconductors. The superconducting properties of carefully grown (chemical transport reaction) single crystals of ZrP1.54S0.46 with a transition temperature of Tc = 3.5 K are investigated. This compound (PbFCl structure type) contains square planar nets: One of the nets is completely occupied (no vacancies) by P, the other one characterized by a random distribution of P and S (full occupation: no vacancies). Besides zero-field-cooling (zfc), field-cooling (fc), and remanent moment (rem) measurements, especially magnetization and ac susceptibility measurements are performed. A nearly ideal type-II behavior with a Ginzburg-Landau parameter κ = 24 is found. The magnetization curves between Bc1 and Bc2 for increasing field are in excellent agreement with theoretical calculations performed by E. H. Brandt based on the Ginzburg-Landau theory. The decreasing branches of the magnetization curves are asymmetric about the field axis indicating weak pinning and also large diamagnetic behavior

Anisotropic superconductivity and quantum oscillations in the layered dichalcogenide TaSnS2

TaSnS2 single crystal and polycrystalline samples are investigated in detail by magnetization, electrical resistivity, and specific heat as well as Raman spectroscopy and nuclear magnetic resonance (NMR). Studies are focused on the temperature and magnetic field dependence of the superconducting state. We determine the critical fields for both directions B∥c and B⊥c. Additionally, we investigate the dependence of the resistivity, the critical temperature, and the structure through Raman spectroscopy under high pressure up to 10 GPa. At a pressure of ≈3GPa the superconductivity is suppressed below our minimum temperature. The Sn NMR powder spectrum shows a single line which is expected for the TaSnS2 phase and confirms the high sample quality. Pronounced de Haas-van Alphen oscillations in the ac susceptibility of polycrystalline sample reveal two pairs of frequencies indicating coexisting small and large Fermi surfaces. The effective mass of the smaller Fermi surface is ≈0.5me. We compare these results with the band structures from DFT calculations. Our findings on TaSnS2 are discussed in terms of a quasi-two-dimensional BCS superconductivity

The study of education between academic discipline and profession

"In der Wissenschaftsforschung werden Lehre und Ausbildung vornehmlich als Reproduktionsinstanzen von Disziplinen verstanden." Die Autoren differenzieren dabei zwischen Ausbildungs- und Forschungswissen. Sie weisen zugleich auf die im Bereich der Erziehungswissenschaften bestehenden Probleme hin. Einerseits gibt es "ausreichend Anlaß, sich mit der Ausbildung unter einer wissenschaftstheoretischen bzw. wissenschaftssoziologischen Perspektive empirisch zu befassen" - andererseits "bedurfte es gerade im Horizont der vielerorts propagierten Besonderheit der Erziehungswissenschaft als Handlungswissenschaft, als praxisbezogene Wissenschaft [...] - einer genaueren Bestimmung des Forschungsgegenstandes, weil nun etwas fraglich wurde, was bislang meist als problemlos vorausgesetzt wurde: die erziehungswissenschaftliche Ausbildung und ihre disziplingenerierende bzw. -erneuernde Funktion". (DIPF/Sch.

Pohl's introduction to physics

This classic textbook on experimental physics, written by Robert W. Pohl to accompany his famous lecture courses, served generations of physics and other science majors, not only in his native Germany, and was for many years a standard textbook. Pohl's lucid and memorable style and his consistent use of vivid demonstration experiments made his textbooks unique in their time. This completely revised and updated modern edition retains his style and clarity in an up-to-date format. The accompanying videos document the original demonstrations and add many modern touches, bringing to life the numerous illustrations in the book and providing an instructive and motivating complement to the text. They are linked to the corresponding topics in the text and can be accessed directly online from the e-book version. Volume 1 covers elementary mechanics, acoustics (vibrations and waves) and thermodynamics. The exercises provide an aid to understanding the material as well as complementary information. This book addresses students of physics and of other natural sciences and engineering, but also teachers and lecturers, who will profit from Pohl's many demonstration experiments, and other interested readers who want to gain an understanding of the fundamentals of physics from an experimental viewpoint.This introductory textbook on experimental physics covers the fields of electrodynamics and optics. It is a new edition of one of the classic textbooks by Robert W. Pohl, written to accompany his famous lecture courses. It served generations of physics and other science majors, not only in his native Germany, and was for many years a standard textbook. Pohl's lucid and memorable style and his consistent use of vivid demonstration experiments made his textbooks unique in their time. This completely revised and updated modern edition attempts to retain his style and clarity in an up-to-date format. The accompanying videos document the original demonstration experiments and add many modern touches, bringing to life the numerous illustrations in the book and providing an instructive and motivating complement to the text. They are linked to the corresponding topics in the text and can be accessed directly online from the e-book version or downloaded to accompany the print version. The clear and structured presentation, always based on experimental demonstrations, gives a lively introduction to the main disciplines in classical physics, here electrodynamics and optics. Although this volume is, like its originals, relatively modest in length, the material it covers often exceeds what is expected of an introductory textbook. Thus the book is suitable not only for undergraduate students and their lecturers, but also for more advanced students and generally interested readers, including teachers at all levels

Influence of ball milling on quasicrystal formation in melt-spun Zr-based glassy ribbons

International audienceThe effect of mechanical deformation on the formation of quasicrystals in Zr57Ti8Nb2.5Cu13.9Ni11.1Al7.5 glassy ribbons has been investigated. The mechanical treatment drastically affects the crystallization behavior and, in particular, suppresses primary quasicrystal formation. However, quasicrystals can be formed by the addition of the appropriate amount of zirconium. This indicates that if a particular short-range (e.g., icosahedral) is required for quasicrystal formation and if this short-range order is altered during milling, it can be restored by appropriately adjusting the chemical composition

Low-frequency spin dynamics as probed by ⁶³Cu and ¹⁹⁹Hg NMR in HgBa₂CuO₄₊δ superconductors with different oxygen content

⁶³Cu and ¹⁹⁹Hg nuclear magnetic resonance was performed on a series of powder HgBa₂CuO₄₊δ samples with different oxygen content δ in order to study the influence of oxygen doping on the spin dynamics in the normal and superconducting state. The spin-lattice relaxation time T₁ of ¹⁹⁹Hg and ⁶³Cu nuclei were measured over a wide range of temperature at different orientations of the crystallites with respect to the magnetic field. For the optimally doped sample (Tc=96 K) we compared our experimental results to numerical calculations of the spin-lattice relaxation rate as a function of temperature below Tc for several types of the order parameter symmetry: isotropic s wave, anisotropic s wave without nodes, s wave with nodes, and d wave, using the different values of the gap parameter 2Δ/kBTc within the AF fluctuation model. The comparison with our experimental relaxation data shows that for ¹⁹⁹Hg nuclei in the orientation B₀∥(a,b) plane as well as for ⁶³Cu nuclei in both orientations, B₀∥(a,b) plane and B₀∥c axis, the experimental results are in coincidence with the dx2₋y2-wave symmetry with the gap parameter 2Δ/kBTc=7.02