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[en] We describe recent and ongoing studies at the National High Magnetic Field Laboratory at Los Alamos using the new '100 Tesla Multi-Shot Magnet', which is presently delivering fields up to ∼89 T during its commissioning. We discuss the first experiments performed in this magnet system, wherein the linewidth of low-temperature photoluminescence spectra was used to directly reveal the degree of magnetic alloy disorder 'seen' by excitons in single Zn0.80Cd0.22Mn0.08Se quantum wells. The magnetic potential landscape in II-VI diluted magnetic semiconductors (DMS) is typically smoothed when the embedded Mn2+ spins align in an applied field. However, an important (but heretofore untested) prediction of current models of compositional disorder is that magnetic alloy fluctuations in many DMS compounds should increase again in very large magnetic fields approaching 100 T. We observed precisely this increase above ∼70 T, in agreement with a simple model of magnetic alloy disorder.
[en] The exciting findings and activities in particle physics in the 50's and 60's will be discussed from an experimentalist's viewpoint. Particular emphasis will be placed on the description of several crucial discoveries (including the omega minus) and on the remarkable insight, guidance, and major contributions of Murray Gell-Mann to the understanding of the symmetry of hadrons which led to the development of the standard model of the strong interactions.
[en] In this paper, the dynamical theory of the edge excitations of generic fractional quantum Hall (FQH) states is summarized and expanded. The low energy effective theory of the edge excitations for the most general abelian FQH states (including spin-unpolarized and multi-layer FQH states) and some non-abelian FQH states is derived using several different methods. The propagators of the electrons and the quasiparticles are calculated for the above FQH states. The microscopic theory of the edge excitations for the Laughlin states is also presented. Some simple applications of the edge theory to the transport properties of the FQH states are discussed
[en] A strong temperature dependent phenomenon of the Josephson plasma resonance mode has been found in high-Tc superconductor Bi2Sr2CaCu2O8+δ in a microwave frequency region between 9 and 50 GHz. The longitudinal plasma frequency sharply decreases and disappears just below Tc. The extrapolated plasma energy is estimated to be bar hωp(0) = 2.59 x 10-4 eV. Since the plasma frequency, ωp, is determined by the Anderson-Higgs-Kibble mechanism and it is expected to be temperature independent, this phenomenon can not be accounted for by the conventional understanding of the plasma mode in superconductors. Experimental results are discussed in terms of the two fluid model, in which the intrinsic Josephson nature of the coupling restricting the tunneling probability of quasiparticles between layers is considered to be as a dumping mechanism of the quasi-particles in this system
[en] It is shown that the free energy and the magnetization of an Ising model in the magnetic field H = iπκT/2 can be obtained directly from corresponding expressions of these quantities in zero field, provided that the latter are known for sufficiently anisotropic interactions. Using this approach the authors derive explicit expression of the free energy and the magnetization at H = iπκT2 for a number of two-dimensional lattices
[en] In this paper the differences in diffraction intensities from some crystal planes in the X-ray diffraction patterns of high-Tc Y-Ba-Cu-O system superconductors prepared by different processing conditions and the difference among various structure cells in references are interpreted using computer fitting. The results suggest that there exists two structure cells in the single phase YBa2Cu3O7-x samples. Both structure cells have the same crystal symmetry and almost the same lattice parameters, a = 3.821A, b = 3.892A and c = 11.676A, but the different distortion degree of Cu2-O plane. According to EPR spectra measured on the same samples, it is considered that the improvement of superconductivity for the samples prepared by two-step annealing in flowing oxygen may be related to concentration of the structure cell with more serious distortion on the Cu2-O plane
[en] X-ray diffraction using anomalous scattering yields to partial interference functions and radial distribution functions for an amorphous Fe90Zr10 alloy. These results are compared with icosahedral models obtained from the curved space approach. A good agreement is observed which supports both X-ray results and theoretical results
[en] Magnetic properties of YBa2Cu3O7-Δν was investigated by dc- and ac-magnetic susceptibility as a function of oxygen deficiency Δy. The susceptibility in the normal state at low temperatures is dominated by the Curie-Weiss law, while the susceptibility at high temperatures deviates from the Curie-Weiss law. The deviations were successfully explained by assuming the triplet spin-pair excitation from the antiferromagnetically coupled Cu2+ ions in the ground state
[en] Electrical, magnetic and crystallographic measurements have been carried out for the pseudoquaternary (Nd1-xPrx)Ba2Cu3O7-δ system. Orthorhombic phase persists from chi = 0.0 up to chi = 0.7 and transforms into the tetragonal structure only for chi ≥ 0.8. Superconducting transition temperature Tc decreases linearly from 92 K for chi = 0.0 to below 10 K for chi = 0.3 and extrapolated to 0 K around chi = 0.35. Magnetic susceptibility indicates that the valence of the Pr ion is close to 4+. Pr4+ is a very powerful oxidizing agent and may distort or move oxygen away from the Cu-O chain and/or the /CuO2 planes and seriously suppress superconductivity