Landau levels, Bardeen polynomials, and Fermi arcs in Weyl semimetals: Lattice-based approach to the chiral anomaly

Condensed matter systems realizing Weyl fermions exhibit striking phenomenology derived from their topologically protected surface states as well as chiral anomalies induced by electromagnetic fields. More recently, inhomogeneous strain or magnetization were predicted to result in chiral electric E-5 and magnetic B-5 fields, which modify and enrich the chiral anomaly with additional terms. In this Rapid Communication, we develop a lattice-based approach to describe the chiral anomaly, which involves Landau and pseudo-Landau levels and treats all anomalous terms on equal footing, while naturally incorporating Fermi arcs. We exemplify its potential by physically interpreting the largely overlooked role of Fermi arcs in the covariant (Fermi level) contribution to the anomaly and revisiting the factor of 1/3 difference between the covariant and consistent (complete band) contributions to the E-5 . B-5 term in the anomaly. Our framework provides a versatile tool for the analysis of anomalies in realistic lattice models as well as a source of simple physical intuition for understanding strained and magnetized inhomogeneous Weyl semimetals

Site-selective measurement of coupled spin pairs in an organic semiconductor

From organic electronics to biological systems, understanding the role of intermolecular interactions between spin pairs is a key challenge. Here we show how such pairs can be selectively addressed with combined spin and optical sensitivity. We demonstrate this for bound pairs of spin-triplet excitations formed by singlet fission, with direct applicability across a wide range of synthetic and biological systems. We show that the site sensitivity of exchange coupling allows distinct triplet pairs to be resonantly addressed at different magnetic fields, tuning them between optically bright singlet (S=0) and dark triplet quintet (S=1,2) configurations: This induces narrow holes in a broad optical emission spectrum, uncovering exchange-specific luminescence. Using fields up to 60 T, we identify three distinct triplet-pair sites, with exchange couplings varying over an order of magnitude (0.3–5 meV), each with its own luminescence spectrum, coexisting in a single material. Our results reveal how site selectivity can be achieved for organic spin pairs in a broad range of systems

Політичні стереотипи та стереотипізація мислення: роль та значення у системі іміджевих комунікацій

Всебічно розглянуто особливості стереотипізації мислення як важливого чинника у процесі сприйняття та аналізу особою або групою осіб суспільно-політичної дійсності. Досліджено природу, джерела та механізми формування політичних стереотипів та показано їх роль і значення у системі іміджевих комунікацій. Наголошено на необхід- ності аналізу існуючої системи стереотипів при створенні іміджу суб’єкта політики.There have been thoroughly examined peculiarities of stereotyping of thinking as an important factor in the process of perception and analysis of socio-political reality by a person or a group of people. There have been investigated the nature, sources and mechanism of political stereotypes formation and showed their role and meaning in the system if image communications. There has been put an emphasis on the necessity of analysis of the existing system of stereotypes while creating the image of a subject of policy

Lock-in detection for pulsed electrically detected magnetic resonance

We show that in pulsed electrically detected magnetic resonance (pEDMR) signal modulation in combination with a lock-in detection scheme can reduce the low-frequency noise level by one order of magnitude and in addition removes the microwave-induced non-resonant background. This is exemplarily demonstrated for spin-echo measurements in phosphorus-doped Silicon. The modulation of the signal is achieved by cycling the phase of the projection pulse used in pEDMR for the read-out of the spin state.Comment: 4 pages, 2 figure

General relativity as an effective field theory: The leading quantum corrections

I describe the treatment of gravity as a quantum effective field theory. This allows a natural separation of the (known) low energy quantum effects from the (unknown) high energy contributions. Within this framework, gravity is a well behaved quantum field theory at ordinary energies. In studying the class of quantum corrections at low energy, the dominant effects at large distance can be isolated, as these are due to the propagation of the massless particles (including gravitons) of the theory and are manifested in the nonlocal/nonanalytic contributions to vertex functions and propagators. These leading quantum corrections are parameter-free and represent necessary consequences of quantum gravity. The methodology is illustrated by a calculation of the leading quantum corrections to the gravitational interaction of two heavy masses.Comment: 34 pages, Latex, UMHEP-40

Щоденники експедиційної роботи Григорія Дем'яна (Вступна стаття та підготовка текстів Василя Сокола)

The interaction between S(-II) and ferric oxides exerts a major control for the sulphur and iron cycle and in particular for the carbon and electron flow in many aquatic systems. It is regarded to be a key reaction leading ultimately to pyrite formation, the pathways still remaining unresolved. We have studied the reaction between lepidocrocite (γ-FeOOH, 21–42 mmol L−1) and dissolved S(-II) (3–9 mmol L−1) in batch experiments at pH 7 in a glove box using TEM, XRD, Mössbauer spectroscopy, and wet chemistry extraction to explore the nanocrystalline products forming at different time steps in close contact to the lepidocrocitesurface. S(0) and acid extractable Fe(II) (Fe(II)HCl) were the main products detected by wet chemistry extraction. The reaction could be divided into three steps: a rapid (<15 min) consumption of dissolved S(-II), formationof S(0) and the build-up of an Fe(II)HCl pool. Then in the absence of dissolved S(-II) concentrations of S(0) and Fe(II)HCl increased only slightly. TEM measurements revealed the occurrence of a mackinawite rim covering the lepidocrocite crystals and being separated from the lepidocrocitesurface by an interfacial magnetite layer that can be regarded as a steady state product of the interaction between lepidocrocite and mackinawite. A significant fraction of Fe(II) was formed in excess to FeS within the first 2 h. The amount of this fraction increased with decreasing ratio between dissolved S(-II) concentration and the concentration ofsurface sites, which we attributed to a kinetic decoupling of S(-II) oxidation and Fe(II) detachment from the lepidocrocitesurface. At low ratios, S(-II) seems to transfer electrons to lepidocrocite faster then stoichiometric amounts of FeS could. After 2 days Fe(II)HCl and S(0) started to decrease resulting in pyrite formation accompanied by traces of magnetite. TEM measurements indicated that mackinawite completely dissolved and precipitation of pyrite occurred dislocated from the lepidocrocitesurface. The absence of dissolved sulphide under these conditions suggest that excess Fe(II) is involved in the formationof polysulphides which are key precursors during pyrite formation. We propose that the occurrence of excess Fe(II) is a common phenomenon particularly in low sulphide – high iron environments attributing significant reactivity to ferric (hydr)oxide

New Approach for Measuring ∣Vub∣|V_{ub}| at Future BB-Factories

It is suggested that the measurements of hadronic invariant mass ($m_X$) distributons in the inclusive $B \rightarrow X_{c(u)} l \nu$ decays can be useful in extracting the CKM matrix element $|V_{ub}|$. We investigated hadronic invariant mass distributions within the various theoretical models of HQET, FAC and chiral lagrangian as well as ACCMM model. It is also emphasized that the $m_X$ distribution even at the region $m_{X} > m_{D}$ in the inclusive $b\rightarrow u$ are effetive in selecting the events, experimentally viable at the future asymmetric $B$ factories, with better theoretical understandings.Comment: 11 pages not including 1 figur

Elucidating the structural composition of a Fe-N-C catalyst by nuclear and electron resonance techniques

Fe–N–C catalysts are very promising materials for fuel cells and metal–air batteries. This work gives fundamental insights into the structural composition of an Fe–N–C catalyst and highlights the importance of an in‐depth characterization. By nuclear‐ and electron‐resonance techniques, we are able to show that even after mild pyrolysis and acid leaching, the catalyst contains considerable fractions of α‐iron and, surprisingly, iron oxide. Our work makes it questionable to what extent FeN4 sites can be present in Fe–N–C catalysts prepared by pyrolysis at 900 °C and above. The simulation of the iron partial density of phonon states enables the identification of three FeN4 species in our catalyst, one of them comprising a sixfold coordination with end‐on bonded oxygen as one of the axial ligands

Two-point function of strangeness-carrying vector-currents in two-loop Chiral Perturbation Theory

We calculate the correlator between two external vector-currents having the quantum-numbers of a charged kaon. We give the renormalized expression to two loops in standard chiral perturbation theory in the isospin limit, which, as a physical result, is finite and scale-independent. Applications include a low energy theorem, valid at two loop order, of a flavor breaking combination of vector current correlators as well as a determination of the phenomenologically relevant finite $O(p^6)$-counterterm combination $Q_V$ by means of inverse moment finite energy sum rules. This determination is less sensitive to isospin-breaking effects than previous attempts.Comment: 24 pages, revtex, 4 figures, 2 tables, revised version, one ref. adde

Precise Prediction for M_W in the MSSM

We present the currently most accurate evaluation of the W boson mass, M_W, in the Minimal Supersymmetric Standard Model (MSSM). The full complex phase dependence at the one-loop level, all available MSSM two-loop corrections as well as the full Standard Model result have been included. We analyse the impact of the different sectors of the MSSM at the one-loop level with a particular emphasis on the effect of the complex phases. We discuss the prediction for M_W based on all known higher-order contributions in representative MSSM scenarios. Furthermore we obtain an estimate of the remaining theoretical uncertainty from unknown higher-order corrections.Comment: 38 pages, 25 figures. Minor corrections, additional reference