Wannier Function Approach to Realistic Coulomb Interactions in Layered Materials and Heterostructures

We introduce an approach to derive realistic Coulomb interaction terms in free standing layered materials and vertical heterostructures from ab-initio modelling of the corresponding bulk materials. To this end, we establish a combination of calculations within the framework of the constrained random phase approximation, Wannier function representation of Coulomb matrix elements within some low energy Hilbert space and continuum medium electrostatics, which we call Wannier function continuum electrostatics (WFCE). For monolayer and bilayer graphene we reproduce full ab-initio calculations of the Coulomb matrix elements within an accuracy of $0.2$eV or better. We show that realistic Coulomb interactions in bilayer graphene can be manipulated on the eV scale by different dielectric and metallic environments. A comparison to electronic phase diagrams derived in [M. M. Scherer et al., Phys. Rev. B 85, 235408 (2012)] suggests that the electronic ground state of bilayer graphene is a layered antiferromagnet and remains surprisingly unaffected by these strong changes in the Coulomb interaction.Comment: 12 pages, 8 figure

Gibt es eine familiale Heimat für Adoptierte?:Verortungsprozesse erwachsener Adoptierter

Adoptierte befinden sich zwischen zwei Familien, Herkunftssystem und Adoptivsystem. Sie streben nach Verbundenheit, einer familialen Heimat. Wie meistern sie diese Situation? Wie gestalten sie ihre Bewältigungsprozesse? Gibt es Bedingungen, wie  Adoptierte eine überdauernde familiale Heimat für sich erwirken können? Auf der Grundlage qualitativer psychologisch-sozialwissenschaftlicher Forschung werden mit der Grounded-Theory-Methodologie narrative Interviews erwachsener Adoptierter analysiert. Bewältigungsprozesse für Verbundenheit sind Verortungsprozesse, diese realisieren die Adoptierten in 3 Phasen. Das Kernstück der Prozesse ist die Verortungsarbeit, an deren Ende Adoptierte ihre Ergebnisse verinnerlichen. Sie erreichen als Resultat des Verortungsprozesses eine stimmige Verortung. Diese wandelt sich durch innere oder äußere Impulse, Adoptierte nehmen die Verortungsarbeit erneut auf. Es gibt keinen finalen Endpunkt der Verortungsarbeit, sie vollzieht sich als Bewältigungsprozess über die Lebensspanne.    <br

Cross-cultural comparison of fertility specific quality of life in German, Hungarian and Jordanian couples attending a fertility center

Background: Only a few studies have reported cross-cultural comparisons regarding psychosocial consequences of infertility. Differences between societies with different cultural backgrounds were revealed and seemed to be based on the importance of pronatalism. Our aim was to measure cross-cultural differences in fertility specific quality of life of infertile couples in Germany, Hungary and Jordan who attend a fertility center in a cross-sectional study. Methods: A cross-sectional study was conducted in one fertility clinic in Germany, in five fertility clinics in Hungary and in one fertility clinic in Jordan. Overall 750 couples (252 couples in Jordan, 246 couples in Germany and 252 couples in Hungary) attending the first medical infertility consultation were asked to fill out our questionnaire set. Fertility specific quality of life (FertiQoL) and sociodemographic differences were measured between couples from three countries. Results: Jordanian couples had the shortest relationship (5.8 ± 4.3 yrs.), though they reported the longest duration of child wish (4.2 ± 3.6 yrs.) and fertility treatments (3.0 ± 3.3 yrs.). The proportion of high education was considerably higher in Jordanian women and men (60 % and 66 %, respectively) compared to the other two samples. First, marked cross-country differences were obtained on Emotional, Mind/Body and Relational subscales of the FertiQoL, indicating that Jordanian couples reported poorer fertility-related quality of life than Germans and Hungarians (p < 0.001). After controlling for the sociodemographic and medical variables, a significant difference only in the Emotional domain was observed (p < 0.001). Conclusions: The study revealed only a few cultural based differences in fertility specific quality of life between the couples of the three countries. Thus, infertility counselors should pay attention to psychosocial problems rooted in individual sociocultural aspects of the infertile couple regardless of cultural stereotypes. Further studies should identify sociocultural factors within different subgroups of infertile patients instead of focusing different societies as a whole because intra-cultural psychosocial differences in experiencing infertility seem to be more important for the individual patient than intercultural differences

Coexisting charge density wave and ferromagnetic instabilities in monolayer InSe

Recently fabricated InSe monolayers exhibit remarkable characteristics that indicate the potential of this material to host a number of many-body phenomena. Here, we consistently describe collective electronic effects in hole-doped InSe monolayers using advanced many-body techniques. To this end, we derive a realistic electronic-structure model from first principles that takes into account the most important characteristics of this material, including a flat band with prominent van Hove singularities in the electronic spectrum, strong electron-phonon coupling, and weakly-screened long-ranged Coulomb interactions. We calculate the temperature-dependent phase diagram as a function of band filling and observe that this system is in a regime with coexisting charge density wave and ferromagnetic instabilities that are driven by strong electronic Coulomb correlations. This regime can be achieved at realistic doping levels and high enough temperatures, and can be verified experimentally. We find that the electron-phonon interaction does not play a crucial role in these effects, effectively suppressing the local Coulomb interaction without changing the qualitative physical picture

PROBING OPTICAL PROPERTIES OF CORRELATED CARBON DEFECTS IN HEXAGONAL-BN BY QUANTUM EMBEDDING APPROACH

In this work we study the optical properties of carbon dimer in bulk hexagonal boron nitride (BN). The utilization of density functional theory and many-body extended Hubbard models revealed the complex spectra, represented by bonding and anti-bonding states in-volved in optical transitions.The work was supported by the grant of the President of the Russian Federation, Project SP-2488.2021.1. The Flatiron Institute is a division of the Simons Foundation

Hydrogen atom moving across a strong magnetic field: analytical approximations

Analytical approximations are constructed for binding energies, quantum-mechanical sizes and oscillator strengths of main radiative transitions of hydrogen atoms arbitrarily moving in magnetic fields 10^{12}-10^{13} G. Examples of using the obtained approximations for determination of maximum transverse velocity of an atom and for evaluation of absorption spectra in magnetic neutron star atmospheres are presented.Comment: 17 pages, 3 figures, 5 tables, LaTeX with IOP style files (included). In v.2, Fig.1 and Table 5 have been corrected. In v.3, a misprint in the fit for oscillator strengths, Eq.(21), has been correcte

Quantum embedding methods for correlated excited states of point defects: Case studies and challenges

A quantitative description of the excited electronic states of point defects and impurities is crucial for understanding materials properties, and possible applications of defects in quantum technologies. This is a considerable challenge for computational methods, since Kohn-Sham density functional theory (DFT) is inherently a ground-state theory, while higher-level methods are often too computationally expensive for defect systems. Recently, embedding approaches have been applied that treat defect states with many-body methods, while using DFT to describe the bulk host material. We implement such an embedding method, based on Wannierization of defect orbitals and the constrained random-phase approximation approach, and perform systematic characterization of the method for three distinct systems with current technological relevance: a carbon dimer replacing a B and N pair in bulk hexagonal BN (CBCN), the negatively charged nitrogen-vacancy center in diamond (NV-), and an Fe impurity on the Al site in wurtzite AlN (FeAl). In the context of these test-case defects, we demonstrate that crucial considerations of the methodology include convergence of the bulk screening of the active-space Coulomb interaction, the choice of exchange-correlation functional for the initial DFT calculation, and the treatment of the "double-counting"correction. For CBCN we show that the embedding approach gives many-body states in agreement with analytical results on the Hubbard dimer model, which allows us to elucidate the effects of the DFT functional and double-counting correction. For the NV- center, our method demonstrates good quantitative agreement with experiments for the zero-phonon line of the triplet-triplet transition. Finally, we illustrate challenges associated with this method for determining the energies and orderings of the complex spin multiplets in FeAl. © 2022 American Physical Society.National Science Foundation, NSF: DMR-1918455; Council on grants of the President of the Russian Federation: SP-2488.2021.1C.E.D. thanks A. Alkauskas, D. Wickramaratne, M. Zingl, A. Gali, M. Turiansky, T. Berkelbach, and A. Millis for fruitful conversations and comments on the manuscript. The Flatiron Institute is a division of the Simons Foundation. C.E.D. acknowledges support from the National Science Foundation under Grant No. DMR-1918455. The work of D.I.B. was supported by the grant of the President of the Russian Federation, Project No. SP-2488.2021.1