Showing papers by "Sebastian Doniach published in 1981"
TL;DR: In this paper, the authors show that fluctuations in the number of Cooper pairs are conjugate to the superconducting phase and can lead to zero-point destruction of phase coherence at zero temperature.
Abstract: For granular metallic films or two-dimensional arrays of Josephson junctions, fluctuations in the number of Cooper pairs are conjugate to the superconducting phase and can lead to zero-point destruction of phase coherence at zero temperature. In two dimensions the resulting critical behavior is shown to be that of the $\ensuremath{\lambda}$ point of $^{4}\mathrm{He}$ in three dimensions, with the charging energy playing the role of temperature. The nature of the quantum \ensuremath{\rightarrow} classical crossover and its effect on the frequency dependence of precursor diamagnetism near the quantum critical point are discussed.
107 citations
TL;DR: Linearly polarized synchrotron radiation has been used to investigate the orientation dependence of the K absorption edge of a single crystal of ammonium dithiomolybdate, the crystal structure of which is also reported in this article.
Abstract: Linearly polarized synchrotron radiation has been used to investigate the orientation dependence of the K absorption edge of a single crystal of ammonium dithiomolybdate, the crystal structure of which is also reported herein. Following the collection of spectra with the polarization vector parallel to the oxygen-oxygen interatomic vector, the sulfur-sulfur vector, and the twofold rotation axis, self-consistent field X..cap alpha.. multiple scattered wave (SCF X..cap alpha.. MSW) calculations were done to interpret the observed orientation dependence. It is shown that this orientation dependence can be used to highlight the edge features which derive from molecular orbitals contributed to principally by the oxygen of the sulfur ligands. Anisotropy is also apparent in the extended X-ray absorption fine structure (EXAFS) spectra, which were recorded for orientations along the S-S and O-O interatomic vectors. It is thus demonstrated that polarized single-crystal X-ray absorption spectroscopy can provide orientationally selective information about the absorbing atom. It could, in principle, be used to deduce certain types of geometric information about the x-ray absorbing species.
76 citations
36 citations