Coupled bipolarons and optical phonons as a model for high-Tc superconductors

The coherence length of the new high-temperature superconductors reaches a small value which is comparable to the dimensions of the unit cell of the compound. This means that a pair consists of two holes occupying the same site or two adjacent sites. Such a situation is described by a model of the local-pairs (bipolarons). The origin of local-pairs may come not only from strong enough electron or hole-phonon interaction but also from other interactions. Independent of the specific nature of such local-pairs, they can undergo a Bose-like condensation to the superconducting state at a critical temperature which is usually much lower than the temperature of the pair formation. An interplay of ferroelectric and superconducting properties is considered within the model of hole-like local-pairs interacting with optical phonons. Therefore, researchers extend the usual local-pair Hamiltonian by including a direct interaction between the local-pairs and the optical phonons. These optical phonons are known to play an important role in the ferroelectric transition and they transform into an additional pseudo-acoustic branch at the ferroelectric critical temperature. (This is associated with nonzero electric polarization due to the existence of two separate lattices composed of negative and positive ions, respectively.

Coupled bipolarons and optical phonons as a model for high-T(sub c) superconductors

The coherence length of the new high-temperature superconductors reaches very small value which is comparable to the dimensions of unit cell of these compounds. This means that a pair consists of two holes occupying the same site or two adjacent sites. Such a situation seems to be described by a model of the local-pairs (bipolarons). The origin of local-pairs may come not only from strong enough electron or hole-phonon interaction but also from other interactions. Independent of the specific nature of such local-pairs, they can undergo a Bose-like condensation to the superconducting state at a critical temperature which is usually much lower than the temperature of the pair formation. An interplay of ferroelectric and superconducting properties is considered within the model of hole-like local-pairs interacting with optical phonons. Therefore, researchers extend the usual local-pair Hamiltonian by including a direct interaction between the local-pairs and the optical phonons. These optical phonons are known to play an important role in the ferroelectric transition, if any, and they transform into an additional pseudo-acoustic branch at the ferroelectric critical temperature. (This is associated with nonzero electric polarization due to the existence of two separate lattices composed of negative and positive ions, respectively.

Spin-stress and spin-strain coupling in diamond-based hybrid spin oscillator systems

Hybrid quantum systems, which combine quantum-mechanical systems with macroscopic mechanical oscillators, have attracted increasing interest as they are well suited as high-performance sensors or transducers in quantum computers. A promising candidate is based on diamond cantilevers, whose motion is coupled to embedded Nitrogen-Vacancy (NV) centers through crystal deformation. Even though this type of coupling has been investigated intensively in the past, several inconsistencies exist in available literature, and no complete and consistent theoretical description has been given thus far. To clarify and resolve these issues, we here develop a complete and consistent formalism to describe the coupling between the NV spin degree of freedom and crystal deformation in terms of stress, defined in the crystal coordinate system XYZ, and strain, defined in the four individual NV reference frames. We find that the stress-based approach is straightforward, yields compact expressions for stress-induced level shifts and therefore constitutes the preferred approach to be used in future advances in the field. In contrast, the strain-based formalism is much more complicated and requires extra care when transforming into the employed NV reference frames. Furthermore, we illustrate how the developed formalism can be employed to extract values for the spin-stress and spin-strain coupling constants from data published by Teissier et al..Comment: 14 pages, 3 figures; SOM available for download under https://quantum-sensing.physik.unibas.ch/publications/research-articles.htm

\u3cem\u3eThe Broken Jug\u3c/em\u3e as an Experiment with Thomas Hobbes\u27 Political Theory

Illinois Wesleyan University recently put on a production of The Broken Jug by John Banville. An amusing, if raunchy, interpretation of the play, it provides a very dark picture of humanity and society. Set in the middle of the nineteenth century in a town called Ballybog (in rural Ireland), it tells of the corrupt Judge Adam who breaks a valuable jug while attempting to make sexual advances on Eve Reck, one of the townspeople. When the case of the broken jug is brought to court, he attempts to blame Robert Temple, another townsperson. After all, the girl he advanced on is the only person who sees him during the entire incident, and she hesitates to blame Judge Adam because it would make others suspect him of the more heinous events that occurred that night; thus, he almost manages to escape

Non-reciprocal coherent dynamics of a single spin under closed-contour interaction

Three-level quantum systems have formed a cornerstone of quantum optics since the discovery of coherent population trapping (CPT) and electromagnetically induced transparency. Key to these phenomena is quantum interference, which arises if two of the three available transitions are coherently driven at well-controlled amplitudes and phases. The additional coherent driving of the third available transition would form a closed-contour interaction (CCI) from which fundamentally new phenomena would emerge, including phase-controlled CPT and one atom interferometry. However, due to the difficulty in experimentally realising a fully coherent CCI, such aspects of three-level systems remain unexplored as of now. Here, we exploit recently developed methods for coherent driving of single Nitrogen-Vacancy (NV) electronic spins to implement highly coherent CCI driving. Our experiments reveal phase-controlled, single spin quantum interference fringes, reminiscent of electron dynamics on a triangular lattice, with the driving field phases playing the role of a synthetic magnetic flux. We find that for suitable values of this phase, CCI driving leads to efficient coherence protection of the NV spin, yielding a nearly two orders of magnitude improvement of the coherence time, even for moderate drive strengths <~1MHz. Our results establish CCI driving as a novel paradigm in coherent control of few-level systems that offers attractive perspectives for applications in quantum sensing or quantum information processing.Comment: 18 pages, 11 figures. Including supplementary material. Comments are welcome. For further information visit https://quantum-sensing.physik.unibas.ch/news.htm

Ökologisierte Landwirtschaft in Deutschland - 2050

Ziel der vorliegenden Studie ist es, eine Diskussionsgrundlage für die Entwicklung einer zukunftsfähigen und ökologisierten Landwirtschaft in Deutschland im Jahr 2050 zu erarbeiten. Diese ökologisierte konventionelle Landwirtschaft zeichnet sich aus durch eine weitgehend klimaschonende Bewirtschaftung, eine deutlichen Erhöhung der Biologischen Vielfalt in der Agrarlandschaft, signifikant verringerte Schadstoffeinträge, eine verbesserte Nutztierhaltung und eine gentechnikfreie und schadstofffreie Erzeugung von hochwertigen Lebensmitteln, Futtermitteln und – falls erforderlich und möglich - von Biomasse. Mit dem Ökolandbau liegt bereits eine gut geeignete Bewirtschaftungsform vor. Es erscheint aber unrealistisch, dass der zertifizierte Ökolandbau bis 2050 die konventionelle Landwirtschaft abgelöst hat. Daher liegt der Schwerpunkt dieser Studie auf der schrittweisen qualitativen Verbesserung der konventionellen Landwirtschaft in den kommenden 35 Jahren bis 2050

Relationship between lead absorption and iron status and its association with oxidative stress markers in lead-exposed workers

Background: The emission of lead (Pb) occurring during the extraction, processing and industrial applications of this element remains a significant environmental risk factor. The absorbability of lead in humans is strongly associated with the general health status of exposed individuals. Existing mineral deficiencies are considered being a predisposition to an increased Pb uptake. Both, iron deficiency and lead poisoning are the major caus-ative factors responsible for the prevalence of anemia within the vulnerable population, especially in children. Although some of the intervention programs of counteracting lead poisoning by iron supplementation proved to be effective in the Pb-exposed population, the exact mechanisms of this interaction still require further studies. The objective of the presented study was to examine the association of iron level on oxidative stress measures and its effects on the severity of lead toxicity in the exposed population. Methods: The analyzed population consisted of 270 male workers from the lead-zinc smelter. The studied pop-ulation was divided into two sub-groups based on the serum iron concentration: low iron level group (L-Fe; Fe median value). Measured traits comprised of blood lead (PbB), serum Fe and zinc protoporphyrin (ZPP) levels as well as a blood count and oxidative stress markers. Results: No significant correlation between serum iron concentration and PbB in the tested cohort was found. On the contrary, the analysis of ZPP levels (long-term marker related to a hematologic toxic effect of Pb) within the subgroups differing in serum Fe level shown that ZPP was 12.3 % lower (p =0.043) in subjects classified within the H-Fe group. A positive correlation of serum Fe and total antioxidant capacity (TAC) was found (R =0.1999). The conducted 3-D PCA analysis showed that individuals classified within the H-Fe group were characterized by the co-occurrence of higher Fe levels, lower ZPP, and higher TAC value. Conclusion: These results support the existing evidence providing that maintaining the optimal status of Fe may play a significant role in preventing the lead poisoning and alleviating harmful effects of Pb on the oxidative balance in humans

Organic farming and the prospects for stimulating public goods under the CAP 2014-2020

The 2013 reform of the Common Agricultural Policy (CAP) for the 2014–2020 period aimed to be a flagship initiative for the delivery of more environmental and climate friendly agriculture, encapsulated in the slogan "public money for public goods”. To achieve its environmental and climate change goals, the EU uses key instruments of Pillars 1 and 2 to provide more public goods from EU agriculture. Organic farming is recognised under both instruments for the first time in terms of its contribution to public goods

Von der Theorie zur Praxis und wieder zurück? : Nachhaltigkeitsbewertung von Politikmaßnahmen

Die Bewertung von Politikmaßnahmen unter Gesichtspunkten der Nachhaltigkeit hat vor dem Hintergrund der EU-Nachhaltigkeitsstrategie stark an Bedeutung gewonnen. Doch welche Rolle spielen Bewertungsinstrumente und welche Potenziale bergen sie