Impact of electric-field dependent dielectric constants on two-dimensional electron gases in complex oxides

High-density two-dimensional electron gas (2DEG) can be formed at complex oxide interfaces such as SrTiO3/GdTiO3 and SrTiO3/LaAlO3. The electric field in the vicinity of the interface depends on the dielectric properties of the material as well as on the electron distribution. However, it is known that electric fields can strongly modify the dielectric constant of SrTiO3 as well as other complex oxides. Solving the electrostatic problem thus requires a self-consistent approach in which the dielectric constant varies according to the local magnitude of the field. We have implemented the field dependence of the dielectric constant in a Schrodinger-Poisson solver in order to study its effect on the electron distribution in a 2DEG. Using the SrTiO3/GdTiO3 interface as an example, we demonstrate that including the field dependence results in the 2DEG being confined closer to the interface compared to assuming a single field-independent value for the dielectric constant. Our conclusions also apply to SrTiO3/LaAlO3 as well as other similar interfaces

Theory of current-driven magnetization dynamics in inhomogeneous ferromagnets

We give a brief account of recent developments in the theoretical understanding of the interaction between electric currents and inhomogeneous ferromagnetic order parameters. We start by discussing the physical origin of the spin torques responsible for this interaction and construct a phenomenological description. We then consider the electric current-induced ferromagnetic instability and domain-wall motion. Finally, we present a microscopic justification of the phenomenological description of current-driven magnetization dynamics, with particular emphasis on the dissipative terms, the so-called Gilbert damping $\alpha$ and the $\beta$ component of the adiabatic current-driven torque.Comment: 25 pages, 2 figures. Will appear in "Current Perspectives" on spin-transfer torque phenomena (edited by Dan Ralph and Mark Stiles), to be published in Journal of Magnetism and Magnetic Material

Emergence of anisotropic Gilbert damping in ultrathin Fe layers on GaAs (001)

As a fundamental parameter in magnetism, the phenomenological Gilbert damping constant a determines the performance of many spintronic devices. For most magnetic materials, a is treated as an isotropic parameter entering the Landau-Lifshitz-Gilbert equation. However, could the Gilbert damping be anisotropic? Although several theoretical approaches have suggested that anisotropic a could appear in single-crystalline bulk systems, experimental evidence of its existence is scarce. Here, we report the emergence of anisotropic magnetic damping by exploring a quasi-two-dimensional single-crystalline ferromagnetic metal/semiconductor interface-that is, a Fe/GaAs(001) heterojunction. The observed anisotropic damping shows twofold C-2v symmetry, which is expected from the interplay of interfacial Rashba and Dresselhaus spin-orbit interaction, and is manifested by the anisotropic density of states at the Fe/GaAs (001) interface. This discovery of anisotropic damping will enrich the understanding of magnetization relaxation mechanisms and can provide a route towards the search for anisotropic damping at other ferromagnetic metal/semiconductor interfaces

The designing of climate protection funds to foster a climate-friendly development of economy and society : conceptual outline of an empirical analysis of German retail investors' preferences

Ausgehend von den Klimaschutzzielen der Bundesrepublik Deutschland untersucht das hier dargestellte Forschungsprojekt, wie Investmentfonds, die in ihren Auswahlkriterien für die Kapitalanlage Ziele des Klimaschutzes berücksichtigen, als Instrument zur Allokation von Kapital von Retail-Anlegern zur Erreichung dieser Klimaschutzziele geeignet sind. Da keine Definition oder ein einheitlicher Standard eines „Klimaschutzfonds“ existiert, sind nicht nur die bereits am Markt vorhandenen Produkte zu analysieren, sondern es ist zudem zu untersuchen, welche Informationen und welches Wissen über solche Fonds und welche Prä-ferenzen in Bezug auf Merkmale dieser Fonds bei den (potentiellen) privaten Anlegern vorhanden sind. Im folgenden Kapitel wird die Problemstellung in ihrem Untersuchungskontext näher erläutert und daraus der Forschungsbedarf abgeleitet und die Forschungsziele definiert. Das dritte Kapitel beschreibt das Konzept für eine empirische Analyse der Präferenzen von Retail-Anlegern in Bezug auf eine Kapitalanlage in Klimaschutz-fonds. Dazu werden die im weiteren Verlauf des hier dargestellten Forschungs-projekts verwendete, methodische Vorgehensweise einer parallelen Conjoint-Analyse erläutert und der inhaltliche Aufbau sowie die Forschungsschwerpunkte der diesem Bericht folgenden Untersuchungen skizziert