Photoemission quasiparticle spectra of Sr2RuO4

Multiband quasiparticle calculations based on perturbation theory and dynamical mean-field methods show that the creation of a photoemission hole state in Sr2RuO4 is associated with a highly anisotropic self-energy. Since the narrow Ru-derived d(xz,yz) bands are more strongly distorted by Coulomb correlations than the wide d(xy) band, charge is partially transferred from d(xz,yz) to d(xy), thereby shifting the d(xy) Van Hove singularity close to the Fermi level.     

The effective Chebotarev density theorem and modular forms modulo

Suppose that (resp. ) is a modular form of integral (resp. half-integral) weight with coefficients in the ring of integers of a number field . For any ideal , we bound the first prime for which (resp. ) is zero ( ). Applications include the solution to a question of Ono (2001) concerning partitions.

     

Double counting in LDA + DMFT—The example of NiO

An intrinsic issue of the LDA + DMFT approach is the so called double counting of interaction terms. How to choose the double-counting potential in a manner that is both physically sound and consistent is unknown. We have conducted an extensive study of the charge-transfer system NiO in the LDA + DMFT framework using quantum Monte Carlo and exact diagonalization as impurity solvers. By explicitly treating the double-counting correction as an adjustable parameter we systematically investigated the effects of different choices for the double counting on the spectral function. Different methods for fixing the double counting can drive the result from Mott insulating to almost metallic. We propose a reasonable scheme for the determination of double-counting corrections for insulating systems.     

Mössbauer studies of after-effects of auger ionization following electron capture in cobalt complexe

Abstract

The electron-capture decay of a cobalt-57 atom triggers an Auger event resulting in the loss of several electrons from the molecule in which it is incorporated. The 14.4 keV Mössbauer emission conveys information regarding the chemical forms in which the daughter iron-57 is ‘stabilized’ within 10^?7 sec following electron capture. During this time the electronic relaxation occurs completely and several tens of electron volt energy is deposited in the molecule as a result of neutralization. We find that the ethylenediamine tetra-acetate, bis-salicylaldehyde tri-ethylenetetramine, acetylacetone, and indenyl chelates fragment in a large majority of events, resulting in the formation of degraded ionic Fe²⁺ and Fe³⁺ in the former cases and C₉H₇Fe⁺ in the latter. On the other hand, highly conjugated compounds such as cobalt phthalocyanine and Vitamin B₁₂ escape fragmentation in 100 per cent of the Auger events. Tris-dipyridyl Co(III) perchlorate also escapes fragmentation in a majority of events. Apparently, the large amount of excitation energy deposited in the molecule as a consequence of charge neutralization is very rapidly (in less than 10^?13sec) and efficiently dispersed through neighboring molecules. It is a novel phenomenon.

When the dipyridyl chelate molecules are dispersed in a foreign matrix, the dissipation of charge and energy is no longer rapid and efficient and the probability of fragmentation is considerably enhanced.

We also find that part of the coordinated parent species, in the case of labeled dipyridyl chelate, arises through fragmentation followed by interaction of the electronically excited degraded iron species with a neighboring chelate molecule resulting in replacement of cobalt with an iron atom. This finding was made possible by using the chelate doped with ‘carrier-free’ ⁵⁷Co citrate.

Emission spectroscopy yields values for the isomer shifts and quadrupole splittings which differ somewhat from those obtained by absorption spectroscopy. The apparent disparities are attributed to the dissimilarities of the matrices in which the Mössbauer emitter or absorber is situated.     

Continuous-time quantum Monte Carlo method for fermions: Beyond auxiliary field framework

A numerically exact continuous-time quantum Monte Carlo algorithm for finite fermionic systems with nonlocal interactions is proposed. The scheme is particularly applicable for general multiband time-dependent correlations, since it does not invoke Hubbard-Stratonovich transformation. The present determinantal grand-canonical method is based on a stochastic series expansion for the partition function in the interaction representation. The results for the Green function and for the time-dependent susceptibility of multiorbital supersymmetric impurity model with a spin-flip interaction are presented.     

Über eine Eigenschaft der klassischen Greenschen Funktion

Ohne Zusammenfassung     

Untersuchungen über die Gleichgewichtsfiguren rotierender Flüssigkeiten,deren Teilchen einander nach dem Newtonschen Gesetze anziehen

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