Comment on half-integer quantum numbers for the total angular momentum of photons in light beams with finite lateral extensions

Recently the spectacular result was derived quantum mechanically that the total angular momentum of photons in light beams with finite lateral extensions can have half-integer quantum numbers. In a circularly polarized Gauss light beam it is half of the spin angular momentum which it would have in a respective infinitely extended wave. In another paper it was shown by a classical calculation that the magnetic moment induced by such a beam in a metal is a factor of two smaller than the one induced by a respective infinitely extended wave. Since the system's angular momentum is proportional to its magnetic moment it could be assumed that the classical result for the magnetic moment reflects the transfer of the total angular momenta of the beam photons to the metal. Here we show that there is no hint that this is indeed the case

Ab-initio investigation of the covalent bond energies in the metallic covalent superconductor MgB2 and in AlB2

The contributions of the covalent bond energies of various atom pairs to the cohesive energy of MgB2 and AlB2 are analysed with a variant of our recently developed energy-partitioning scheme for the density-functional total energy. The covalent bond energies are strongest for the intralayer B-B pairs. In contrast to the general belief, there is also a considerable covalent bonding between the layers, mediated by the metal atom. The bond energies between the various atom pairs are analysed in terms of orbital- and energy-resolved contributions.Comment: 6 pages, 1 figure, 2 tables, submitted to PR

Derivation of phenomenological expressions for transition matrix elements for electron-phonon scattering

In the literature on electron-phonon scatterings very often a phenomenological expression for the transition matrix element is used which was derived in the textbooks of Ashcroft/Mermin and of Czycholl. There are various steps in the derivation of this expression. In the textbooks in part different arguments have been used in these steps, but the final result is the same. In the present paper again slightly different arguments are used which motivate the procedure in a more intuitive way. Furthermore, we generalize the phenomenological expression to describe the dependence of the matrix elements on the spin state of the initial and final electron state

Physical and mathematical justification of the numerical Brillouin zone integration of the Boltzmann rate equation by Gaussian smearing

Scatterings of electrons at quasiparticles or photons are very important for many topics in solid state physics, e.g., spintronics, magnonics or photonics, and therefore a correct numerical treatment of these scatterings is very important. For a quantum-mechanical description of these scatterings Fermi's golden rule is used in order to calculate the transition rate from an initial state to a final state in a first-order time-dependent perturbation theory. One can calculate the total transition rate from all initial states to all final states with Boltzmann rate equations involving Brillouin zone integrations. The numerical treatment of these integrations on a finite grid is often done via a replacement of the Dirac delta distribution by a Gaussian. The Dirac delta distribution appears in Fermi's golden rule where it describes the energy conservation among the interacting particles. Since the Dirac delta distribution is a not a function it is not clear from a mathematical point of view that this procedure is justified. We show with physical and mathematical arguments that this numerical procedure is in general correct, and we comment on critical points

Unifying ultrafast demagnetization and intrinsic Gilbert damping in Co/Ni bilayers with electronic relaxation near the Fermi surface

The ability to controllably manipulate the laser-induced ultrafast magnetic dynamics is a prerequisite for future high speed spintronic devices. The optimization of devices requires the controllability of the ultrafast demagnetization time, , and intrinsic Gilbert damping, . In previous attempts to establish the relationship between and , the rare-earth doping of a permalloy film with two different demagnetization mechanism is not a suitable candidate. Here, we choose Co/Ni bilayers to investigate the relations between and by means of time-resolved magneto-optical Kerr effect (TRMOKE) via adjusting the thickness of the Ni layers, and obtain an approximately proportional relation between these two parameters. The remarkable agreement between TRMOKE experiment and the prediction of breathing Fermi-surface model confirms that a large Elliott-Yafet spin-mixing parameter is relevant to the strong spin-orbital coupling at the Co/Ni interface. More importantly, a proportional relation between and in such metallic films or heterostructures with electronic relaxation near Fermi surface suggests the local spin-flip scattering domains the mechanism of ultrafast demagnetization, otherwise the spin-current mechanism domains. It is an effective method to distinguish the dominant contributions to ultrafast magnetic quenching in metallic heterostructures by investigating both the ultrafast demagnetization time and Gilbert damping simultaneously. Our work can open a novel avenue to manipulate the magnitude and efficiency of Terahertz emission in metallic heterostructures such as the perpendicular magnetic anisotropic Ta/Pt/Co/Ni/Pt/Ta multilayers, and then it has an immediate implication of the design of high frequency spintronic devices

Business Value of the Internet of Things – A Project Portfolio Selection Approach

The Internet of Things (IoT) counts among the most disruptive digital technologies on the market. De-spite the IoT’s emerging nature, there is an increasing body of knowledge related to technological and business topics. Nevertheless, there is a lack of prescriptive knowledge that provides organizations with guidance on the economic valuation of investments in the IoT perspective. Such knowledge, however, is crucial for pursuing the organizational goal of long-term value maximization. Against this backdrop, we develop an economic decision model that helps organizations determine an optimal IoT project port-folio from a manufacturer’s perspective and complies with the principles of project portfolio selection and value-based management. For our purposes, IoT project portfolios are compilations of projects that aim to implement IoT technology in an organization’s production process, products, or infrastructure. Our decision model schedules IoT projects for multiple planning periods and considers monetary as well as monetized project effects. On this foundation, it determines the project sequence with the highest value contribution. To evaluate our decision model, we discussed its real-world fidelity and under-standability with an industry expert renowned for its proficiency in IoT technology, implemented a soft-ware prototype, and demonstrated its applicability based on real-world data. Keywords: Internet of Things, economic valuation of IoT, value-based management, project portfolio management

Versorgungsqualität bei polytraumatisierten Patienten in einem nichtuniversitären Überregionalen Traumazentrum

Die Klinik für Unfallchirurgie und Orthopädie des Krankenhauses St. Elisabeth Ravensburg nimmt als Überregionales Traumazentrum eine wichtige Stellung im Rahmen der Schwerstverletzten – Versorgung ein. Die vorliegende Arbeit beschäftigt sich mit der Versorgungsqualität polytraumatisierter Patienten im Krankenhaus St. Elisabeth als einem nichtuniversitären Überregionalen Traumazentrum. Insbesondere wurde der Behandlungserfolg anhand des Patientenguts und der Unfallursache, sowie dem Verletzungsspektrum untersucht. Zusätzlich die Art des Transports, die benötigte Transportzeit vom Unfallort bis in den Schockraum, die dort durchgeführte Diagnostik und die Dauer der Schockraumphase evaluiert. Insgesamt konnten n = 73 Patienten, welche im Jahr 2012 über den Schockraum im Krankenhaus St. Elisabeth Ravensburg stationär aufgenommen worden waren, in die retrospektive Studie eingeschlossen werden, n = 54 dieser Patienten waren polytraumatisiert mit einem ISS ≥ 16 Punkten. Außerdem wurden die Daten einer Notarztumfrage zur Zufriedenheit der Schockraumversorgung von polytraumatisierten Patienten in die Auswertung miteinbezogen. Der Vergleich der Daten der Patienten des Krankenhauses St. Elisabeth Ravensburg mit den Daten des Traumaregisters DGU® führte zu folgendem Ergebnis: Die im Jahr 2012 im Krankenhaus St. Elisabeth Ravensburg festgestellte höhere Sterblichkeit der polytraumatisierten Patienten im Vergleich mit dem Bundesdurchschnitt des Traumaregisters erklärt sich durch eine deutlich höhere durchschnittliche Verletzungsschwere und vor allem auch häufigeren schweren Schädelhirntraumata

Electronic correlations in vanadium chalcogenides: BaVSe3 versus BaVS3

Albeit structurally and electronically very similar, at low temperature the quasi-one-dimensional vanadium sulfide BaVS3 shows a metal-to-insulator transition via the appearance of a charge-density-wave state, while BaVSe3 apparently remains metallic down to zero temperature. This different behavior upon cooling is studied by means of density functional theory and its combination with the dynamical mean-field theory and the rotationally-invariant slave-boson method. We reveal several subtle differences between these chalcogenides that provide indications for the deviant behavior of BaVSe3 at low temperature. In this regard, a smaller Hubbard U in line with an increased relevance of the Hund's exchange J plays a vital role.Comment: 16 pages, 11 figures, published versio