Protective capping of topological surface states of intrinsically insulating Bi2_2Te3_3

We have identified epitaxially grown elemental Te as a capping material that is suited to protect the topological surface states of intrinsically insulating Bi$_2$Te$_3$. By using angle-resolved photoemission, we were able to show that the Te overlayer leaves the dispersive bands of the surface states intact and that it does not alter the chemical potential of the Bi$_2$Te$_3$ thin film. From in-situ four-point contact measurements, we observed that the conductivity of the capped film is still mainly determined by the metallic surface states and that the contribution of the capping layer is minor. Moreover, the Te overlayer can be annealed away in vacuum to produce a clean Bi$_2$Te$_3$ surface in its pristine state even after the exposure of the capped film to air. Our findings will facilitate well-defined and reliable ex-situ experiments on the properties of Bi$_2$Te$_3$ surface states with nontrivial topology.Comment: 5 pages, 5 figures, 2 pages supplemental material accepted for publication in AIP Advance

Chthonius (Ephippiochthonius) poeninus : a “Swiss endemic species” in the Allgäu Alps (Pseudoscorpiones: Chthoniidae)

In the course of a long term survey on the effects of grazing on the diversity of alpine grasslands, the false scorpion Chthonius (Ephippiochthonius) poeninus Mahnert, 1979 was recorded for the first time outside of Switzerland. The preferred habitat at the locality Alpe Einödsberg (Germany, Bavaria) differs strongly from previous findings. Our data suggest an association with Nardus grasslands (Geo montani-Nardetum), whereas earlier records originated from leaf litter, moss and mouldy trunks. Furthermore, the new records between 1540 m and 1973 m above sea level are the first from the subalpine region of the Alps (hitherto C. poeninus was known from 550 m to 1450 m). In the study region, extensive grazing seems to have a positive effect on the abundance of the species, while it is missing from intensively grazed pastures

Intrinsic conduction through topological surface states of insulating Bi2_2Te3_3 epitaxial thin films

Topological insulators represent a novel state of matter with surface charge carriers having a massless Dirac dispersion and locked helical spin polarization. Many exciting experiments have been proposed by theory, yet, their execution have been hampered by the extrinsic conductivity associated with the unavoidable presence of defects in Bi$_2$Te$_3$ and Bi$_2$Se$_3$ bulk single crystals as well as impurities on their surfaces. Here we present the preparation of Bi$_2$Te$_3$ thin films that are insulating in the bulk and the four-point probe measurement of the conductivity of the Dirac states on surfaces that are intrinsically clean. The total amount of charge carriers in the experiment is of order 10$^{12}$ cm$^{-2}$ only and mobilities up to 4,600 cm$^2$/Vs have been observed. These values are achieved by carrying out the preparation, structural characterization, angle-resolved and x-ray photoemission analysis, and the temperature dependent four-point probe conductivity measurement all in-situ under ultra-high-vacuum conditions. This experimental approach opens the way to prepare devices that can exploit the intrinsic topological properties of the Dirac surface states.Comment: accepted for publication in Proceedings of the National Academy of Sciences of the United States of America (PNAS

h→ggh\to gg and h→γγh\to\gamma\gamma with Anomalous Couplings at Next-to-Leading Order in QCD

We generalize the next-to-leading order QCD calculations for the decay rates of $h\to gg$ and $h\to\gamma\gamma$ to the case of anomalous couplings of the Higgs boson. We demonstrate how this computation can be done in a consistent way within the framework of an electroweak chiral Lagrangian, based on a systematic power counting. It turns out that no additional coupling parameters arise at NLO in QCD beyond those already present at leading order. The impact of QCD is large for $h\to gg$ and the uncertainties from QCD are significantly reduced at NLO. $h\to\gamma\gamma$ is only mildly affected by QCD; here the NLO treatment practically eliminates the uncertainties. Consequently, our results will allow for an improved determination of anomalous Higgs couplings from these processes. The relation of our framework to a treatment in Standard Model effective field theory is also discussed.Comment: Additional references included. 41 pages, 11 figures, 8 Table

Strain control of hybridization between dark and localized excitons in a 2D semiconductor

Mechanical strain is a powerful tuning knob for excitons, Coulomb-bound electron-hole complexes dominating optical properties of two-dimensional semiconductors. While the strain response of bright free excitons is broadly understood, the behavior of dark free excitons (long-lived excitations that generally do not couple to light due to spin and momentum conservation) or localized excitons related to defects remains mostly unexplored. Here, we develop a technique capable of straining pristine suspended WSe2 kept at cryogenic temperatures up to 3\% to study the strain behavior of these fragile many-body states. We find that under the application of strain, dark and localized excitons in monolayer WSe2 - a prototypical 2D semiconductor - are brought into energetic resonance, forming a new hybrid state that inherits the properties of the constituent species. The characteristics of the hybridized state, including an order-of-magnitude enhanced light/matter coupling, avoided-crossing energy shifts, and strain tunability of many-body interactions, are all supported by first-principles calculations. The hybridized exciton reported here may play a critical role in the operation of single quantum emitters based on WSe2. Furthermore, the techniques we developed may be used to fingerprint unidentified excitonic statesComment: 15 pages, 5 figure

Strain control of hybridization between dark and localized excitons in a 2D semiconductor

The interface between a ferro- or ferrimagnetic insulator and a normal metal can support spin currents polarized collinear with and perpendicular to the magnetization direction. The flow of angular momentum perpendicular to the magnetization direction (“transverse” spin current) takes place via spin torque and spin pumping. The flow of angular momentum collinear with the magnetization (“longitudinal” spin current) requires the excitation of magnons. In this article we extend the existing theory of longitudinal spin transport [Bender and Tserkovnyak, Phys. Rev. B 91, 140402(R) (2015)] in the zero-frequency weak-coupling limit in two directions: We calculate the longitudinal spin conductance nonperturbatively (but in the low-frequency limit) and at finite frequency (but in the limit of low interface transparency). For the paradigmatic spintronic material system YIG|Pt, we find that nonperturbative effects lead to a longitudinal spin conductance that is ca. 40% smaller than the perturbative limit, whereas finite-frequency corrections are relevant at low temperatures ≲100K only, when only few magnon modes are thermally occupied

A compact ion-trap quantum computing demonstrator

Quantum information processing is steadily progressing from a purely academic discipline towards applications throughout science and industry. Transitioning from lab-based, proof-of-concept experiments to robust, integrated realizations of quantum information processing hardware is an important step in this process. However, the nature of traditional laboratory setups does not offer itself readily to scaling up system sizes or allow for applications outside of laboratory-grade environments. This transition requires overcoming challenges in engineering and integration without sacrificing the state-of-the-art performance of laboratory implementations. Here, we present a 19-inch rack quantum computing demonstrator based on $^{40}\textrm{Ca}^+$ optical qubits in a linear Paul trap to address many of these challenges. We outline the mechanical, optical, and electrical subsystems. Further, we describe the automation and remote access components of the quantum computing stack. We conclude by describing characterization measurements relevant to digital quantum computing including entangling operations mediated by the Molmer-Sorenson interaction. Using this setup we produce maximally-entangled Greenberger-Horne-Zeilinger states with up to 24 ions without the use of post-selection or error mitigation techniques; on par with well-established conventional laboratory setups

Joh. Cyriaci Hoferi, Pastoris zu Kalkhorst in Mecklenburg; Klärlich gezeigter Himmels-Weg, das ist: Wie ein Kind in 24. Stunden lernen kan, wie es soll der Höllen entgehen und selig werden

JOH. CYRIACI HOFERI, PASTORIS ZU KALKHORST IN MECKLENBURG; KLÄRLICH GEZEIGTER HIMMELS-WEG, DAS IST: WIE EIN KIND IN 24. STUNDEN LERNEN KAN, WIE ES SOLL DER HÖLLEN ENTGEHEN UND SELIG WERDEN Joh. Cyriaci Hoferi, Pastoris zu Kalkhorst in Mecklenburg; Klärlich gezeigter Himmels-Weg, das ist: Wie ein Kind in 24. Stunden lernen kan, wie es soll der Höllen entgehen und selig werden ([1]) Einband ( - ) Titelseite ([1]) Vorrede an den Leser. ([3]) Vom Eingang des heiligen Catechismi (6) Von den zehen Geboten (7) Von der Sünde (28) Von der Busse (29) Von den guten Wercken (30) Vom Christlichen Glauben (31) Von Gott (33) Von der Schöpffung (35) Von den Engeln (37) Von dem Menschen (39) Von der Vorsorge Gottes (41) Von der Person Christi (43) Vom Amte Christi (47) Vom Leyden und Sterben Christi (48) Vom Begräbniß Christi (50) Von der Höllenfahrt Christi (51) Von der Auferstehung Christi (51) Von der Himmelfahrt Christi (52) Vom Jüngsten Gericht (53) Vom heiligen Geist (56) Vom freyen Willen des Menschen (57) Von der Christlichen Kirchen (58) Von der Auferstehung der Todten (62) Von dem ewigen Leben (63) Von der Hölle (65) Vom Vater Unser (67) Von der Tauffe (82) Von der Beichte (87) Vom Sacrament des Altars (89) Morgen-Abend- und Tisch-Gebete (93) Die sieben Buß-Psalmen (107

Digitale Schule regional gestalten

DIGITALE SCHULE REGIONAL GESTALTEN Digitale Schule regional gestalten / Hense, Julia (CC BY-SA) ( -