Towards a theory of surface orbital magnetization

The theory of bulk orbital magnetization has been formulated both in reciprocal space based on Berry curvature and related quantities, and in real space in terms of the spatial average of a quantum mechanical local marker. Here we consider a three-dimensional antiferromagnetic material having a vanishing bulk but a nonzero surface orbital magnetization. We ask whether the surface-normal component of the surface magnetization is well defined, and if so, how to compute it. As the physical observable corresponding to this quantity, we identify the macroscopic current running along a hinge shared by two facets. However, the hinge current only constrains the difference of the surface magnetizations on the adjoined facets, leaving a potential ambiguity. By performing a symmetry analysis, we find that only crystals exhibiting a pseudoscalar symmetry admit well-defined magnetizations at their surfaces at the classical level. We then explore the possibility of computing surface magnetization via a coarse-graining procedure applied to a quantum local marker. We show that multiple expressions for the local marker exist, and apply constraints to filter out potentially meaningful candidates. Using several tight-binding models as our theoretical test bed and several potential markers, we compute surface magnetizations for slab geometries and compare their predictions with explicit calculations of the macroscopic hinge currents of rod geometries. We find that only a particular form of the marker consistently predicts the correct hinge currents.Comment: 26 pages, 12 figure

Cyclic Ferroelectric Switching and Quantized Charge Transport in CuInP2_2S6_6

The van der Waals layered ferroelectric CuInP$_2$S$_6$ has been found to exhibit a variety of intriguing properties arising from the fact that the Cu ions are unusually mobile in this system. While the polarization switching mechanism is usually understood to arise from Cu ion motion within the monolayers, a second switching path involving Cu motion across the van der Waals gaps has been suggested. In this work, we perform zero-temperature first-principles calculations on such switching paths, focusing on two types that preserve the periodicity of the primitive unit cell: ``cooperative" paths preserving the system's glide mirror symmetry, and ``sequential" paths in which the two Cu ions in the unit cell move independently of each other. We find that CuInP$_2$S$_6$ features a rich and varied energy landscape, and that sequential paths are clearly favored energetically both for cross-gap and through-layer paths. Importantly, these segments can be assembled to comprise a globally insulating cycle with the out-of-plane polarization evolving by a quantum as the Cu ions shift to neighboring layers. In this sense, we argue that CuInP$_2$S$_6$ embodies the physics of a quantized adiabatic charge pump

Development, Production and Testing of 4500 Beam Loss Monitors

Beam-loss monitoring (BLM) [1] is a key element in the LHC machine protection. 4250 nitrogen filled ionization chambers (IC) and 350 secondary emission monitors (SEM) have been manufactured and tested at the Institute for High Energy Physics (IHEP) in Protvino, Russia, following their development at CERN. Signal speed and robustness against aging were the main design criteria. Each monitor is permanently sealed inside a stainless-steel cylinder. The quality of the welding was a critical aspect during production. The SEMs are requested to hold a vacuum of $10^{-7}$ bar. Impurity levels from thermal and radiationinduced desorption should remain in the range of parts per million in the ICs. To avoid radiation aging (up to $2·10^{8}$ Gy in 20 years) production of the chambers followed strict UHV requirements. IHEP designed and built the UHV production stand. Due to the required dynamic range of $10^{8}$, the leakage current of the monitors has to stay below 2 pA. Several tests during and after production were performed at IHEP and CERN. A consistently high quality during the whole production period was achieved and the tight production schedule kept at the same time

Comprehensive Analysis of The Activities of Russian Federal Universities

This article aims to fully investigate the activities of the Federal Universities of Russia in the context of various aspects of development and to find appropriate comprehensive assessment methods that can be applied to modern universities that meet the best global standards. The main methods of research are comparative analysis and the formation of qualimetric models based on synthetically selected evaluation criteria. Structural changes in the activities of Russian federal universities have been analyzed. Authors analyze scientific, educational and social activities and other parameters. Particular attention is paid to the development of the ecosystem of innovations in Russian federal universities, its constituent elements and the peculiarities of their functioning. The study provides an opportunity to combine various aspects in the model of university activities. The article presents a comparative analysis of the development of federal universities and their ranking by integrated assessment. The development of communication channels between the academic community and mass audiences was analyzed, also the publication activity of federal universities was evaluated. The authors propose the main methods and sources of collection, processing and verification of disparate information on the state of innovation ecosystems in Russian federal universities. The proposed methodology, unlike existing approaches, allows a comprehensive assessment of the successful and underdeveloped activities of modern universities in both statistics and dynamics. The conclusion of the work is the need for a comprehensive analysis of federal universities by building a qualification parametric model on a regular basis