Dependence of transport coefficients of Yb(Rh1−x_{1-x}Cox_x)2_2Si2_2 intermetallics on temperature and cobalt concentration

Dependence of transport coefficients of the Yb(Rh$_{1-x}$Co$_x$)$_2$Si$_2$ series of alloys on temperature and cobalt concentration is explained by an asymmetric Anderson model which takes into account the exchange scattering of conduction electrons on ytterbium ions and the splitting of 4$f$-states by the crystalline electric field (CEF). The substitution of rhodium by cobalt is described as an increase of chemical pressure which reduces the exchange coupling and the CEF splitting. The scaling analysis and numerical NCA solution of the model show that the effective degeneracy of the 4$f$-state at a given temperature depends on the relative magnitude of the Kondo scale and the CEF splitting. Thus, we find that dependence of the thermopower, $S(T)$, on temperature and cobalt concentration can be understood as an interplay of quantum fluctuations, driven by the Kondo effect, and thermal fluctuations, which favor a uniform occupation of the CEF states. The theoretical model captures all the qualitative features of the experimental data and it explains the evolution of the shape of $S(T)$ with the increase of cobalt concentration.Comment: 8 pages, 4 figure

Zwischenergebnisse eines Blattdüngungsversuches im Ökologischen Apfelanbau bei 'Elstar'

Aufgrund der geringen Erträge, die im ökologischen Apfelanbau erzielt werden, kam die Frage auf, was die Gründe dafür sein könnten. In den Diskussionen wird oftmals auf den schlechten Zustand der Apfelbäume hingewiesen. Die Bäume würden einen gestressten Eindruck machen. Als Ursache werden meist aggressive Pflanzenschutzmittel und ungenügende Ernährungszustände in den wichtigen Entwicklungsphasen genannt. Voruntersuchungen zu diesem Versuch, hinsichtlich der Blütequalität, wiesen darauf hin, dass es im ökologischen Apfelanbau um die Blütenqualität nicht zum Besten zu stehen scheint. Zwar werden meist eine ausreichende Anzahl an Blütenständen ausgebildet, häufig auch zu viele, jedoch bilden diese Blüten keine erntefähigen Früchte aus. Frühere Untersuchungen zur Blattdüngung weisen darauf hin, dass unter bestimmten Voraussetzungen wie z.B. Mangelkrankheiten und Stresssituationen (Witterung, hoher Ertrag etc.) Blattdüngungen im Herbst nach der Ernte oder im Frühjahr vor der Blüte eine positive Wirkung auf das Ertragsverhalten von Apfelbäumen haben können. Dieser Versuch sollte daher klären, ob im ökologischen Apfelanbau der Ertrag über die Blattdüngung zu beeinflussen ist

Kostenkalkulation im ökologischen Apfelanbau

In Deutschland wird unter den heutigen Gesichtpunkten seit etwa 1960 ökologischer Obstbau betrieben. Um die Rentabilität einer Kultur zu überprüfen. wurde im konventionellen und nach seiner Einführung auch im integrierten Obstbau frühzeitig damit begonnen. Daten wie Erträge. Arbeitsgange und deren Kosten zu erfassen. Um eine Datengrundlage für die Beratung im ökologischen Obstbau zu haben, war für die damaligen Berater des ökologischen Obstbauberatungsdienstes e.v. an der LVWO Weinsberg, Stefanie Magens und Michael Straub der Anlass, eine Arbeitszeiterhebung bezüglich Arbeitsgängen und Zeiten für Baden-Württemberg anzuregen. Hinzu kam das steigende' Interesse an der ökologischen Obstproduktion von Betrieben. die in die ökologische Obstproduktion einsteigen wollten

Heavy Fermions and Quantum Phase Transitions

Quantum phase transitions arise in many-body systems due to competing interactions that promote rivaling ground states. Recent years have seen the identification of continuous quantum phase transitions, or quantum critical points, in a host of antiferromagnetic heavy-fermion compounds. Studies of the interplay between the various effects have revealed new classes of quantum critical points, and are uncovering a plethora of new quantum phases. At the same time, quantum criticality has provided fresh insights into the electronic, magnetic, and superconducting properties of the heavy-fermion metals. We review these developments, discuss the open issues, and outline some directions for future research.Comment: review article, 26 pages, 4 figure

Superconductivity in heavy fermion compounds

We review the current state of experimental and theoretical investigations of heavy fermion superconductors. We discuss most of the Ce-based compounds like Ce122, Ce115, Ce218 and Ce131 classes and U-based superconductors like UBe_13 and UPd_2Al_3. In the former the emphasis is on the connection to quantum critical phenomena and non-Fermi liquid behaviour. Recent neutron scattering and hydrostatic pressure results on SDW/SC competition in the Ce122 system are included. For the U-compounds we discuss the significance of dual models with both localised and itinerant 5f electrons for mass enhancement and superconducting pair formation. Itinerant spin fluctuation theories for unconventional superconductivity are also reviewed.Comment: 74 pages, 29 figures. For a version of the manuscript including higher-resolution figures, see http://www.cpfs.mpg.de/~thalm/SCMaterials.pd

Multidimensional entropy landscape of quantum criticality

The Third Law of Thermodynamics states that the entropy of any system in equilibrium has to vanish at absolute zero temperature. At nonzero temperatures, on the other hand, matter is expected to accumulate entropy near a quantum critical point (QCP), where it undergoes a continuous transition from one ground state to another. Here, we determine, based on general thermodynamic principles, the spatial-dimensional profile of the entropy S near a QCP and its steepest descent in the corresponding multidimensional stress space. We demonstrate this approach for the canonical quantum critical compound CeCu6-xAux near its onset of antiferromagnetic order. We are able to link the directional stress dependence of S to the previously determined geometry of quantum critical fluctuations. Our demonstration of the multidimensional entropy landscape provides the foundation to understand how quantum criticality nucleates novel phases such as high-temperature superconductivity.Comment: 14 pages, 4 figure

The crossed-field and single-field Hall effect in LuRh2Si2

The Hall effect of LuRh2Si2--the non-magnetic homologue of the heavy-fermion material YbRh2Si2--is studied with two different setups: In the conventional single-field geometry, the field dependence is analyzed in terms of the differential Hall coefficient. Beyond that, the recently developed crossed-field experiment allows to examine the linear-response Hall coefficient as a function of magnetic field. The results reveal the expected analogy between both experiments which corroborates the equivalent findings in YbRh2Si2. This emphasizes the applicability to investigate field-induced quantum critical points with both methods.Comment: 4 pages, 3 figures, accepted for publication in physica status solidi to QCNP200

Expatriate Adjustment of U.S. Military on Foreign Assignment:The Role of Personality and Cultural Intelligence in Adjustment

The present study explored the relationships between personality, cultural intelligence, and adjustment to expatriate assignments. More narrowly, this study explored which facets of cultural intelligence are related to United States Air Force (USAF) members\u27 adjustment to international assignments in Germany. The study also aimed to clarify the relationship between Big Five personality factors and adjustment in USAF expatriates. Expatriate adjustment was measured using the Expatriate Adjustment Scale by Black and Stephens (1989). Cultural Intelligence was measured using the Extended Cultural Intelligence Scale by Van Dyne, Ang, Ng, Rockstuhl, Tan, and Koh (2012). Big Five personality factors were measured using the International Personality Item Pool by Goldberg, Johnson, Eber, Hogan, Ashton, Cloninger, & Gough (2006). There were 64 respondents to the electronic survey distributed to Spangdhalem Air Base. The results indicated that significant positive relationships were found between ten sub facets of cultural intelligence and adjustment. No significant relationships between Big Five personality factors and adjustment were found in this study