Ultrafast switching to a stable hidden topologically protected quantum state in an electronic crystal

Hidden states of matter with novel and unusual properties may be created if a system out of equilibrium can be induced to follow a trajectory to a state which is inaccessible or does not even exist under normal equilibrium conditions. Here we report on the discovery of a hidden (H) topologically protected electronic state in a layered dichalcogenide 1T-TaS2 crystal reached as a result of a quench caused by a single 35 fs laser pulse. The properties of the H state are markedly different from any other state of the system: it exhibits a large drop of electrical resistance, strongly modified single particle and collective mode spectra and a marked change of optical reflectivity. Particularly important and unusual, the H state is stable for an arbitrarily long time until a laser pulse, electrical current or thermal erase procedure is applied, causing it to revert to the thermodynamic ground state. Major observed events can be reproduced by a kinetic model describing the conversion of photo excited electrons and holes into an electronically ordered crystal, thus converting a Mott insulator to a conducting H state. Its long-time stability follows from the topological protection of the number of periods in the electronic crystal.Comment: 21 pages and 5 figures, separate supplementary materia

Ultrafast manipulation of the NiO antiferromagnetic order via sub gap optical excitation

Wide band gap insulators such as NiO offer the exciting prospect of coherently manipulating electronic correlations with strong optical fields. Contrary to metals where rapid dephasing of optical excitation via electronic processes occurs, the sub gap excitation in charge transfer insulators has been shown to couple to low energy bosonic excitations. However, it is currently unknown if the bosonic dressing field is composed of phonons or magnons. Here we use the prototypical charge transfer insulator NiO to demonstrate that 1.5 eV sub gap optical excitation leads to a renormalised NiO band gap in combination with a significant reduction of the antiferromagnetic order. We employ element specific X ray reflectivity at the FLASH free electron laser to demonstrate the reduction of the upper band edge at the O 1s 2p core valence resonance K edge whereas the antiferromagnetic order is probed via X ray magnetic linear dichroism XMLD at the Ni 2p 3d resonance L2 edge . Comparing the transient XMLD spectral line shape to ground state measurements allows us to extract a spin temperature rise of 65 5 K for time delays longer than 400 fs while at earlier times a non equilibrium spin state is formed. We identify transient mid gap states being formed during the first 200 fs accompanied by a band gap reduction lasting at least up to the maximum measured time delay of 2.4 ps. Electronic structure calculations indicate that magnon excitations significantly contribute to the reduction of the NiO band ga

Ultrafast modification of the electronic structure of a correlated insulator

A nontrivial balance between Coulomb repulsion and kinematic effects determines the electronic structure of correlated electron materials. The use of electromagnetic fields strong enough to rival these native microscopic interactions allows us to study the electronic response as well as the time scales and energies involved in using quantum effects for possible applications. We use element specific transient x ray absorption spectroscopy and high harmonic generation to measure the response to ultrashort off resonant optical fields in the prototypical correlated electron insulator NiO. Surprisingly, fields of up to 0.22 V lead to no detectable changes in the correlated Ni 3d orbitals contrary to previous predictions. A transient directional charge transfer is uncovered, a behavior that is captured by first principles theory. Our results highlight the importance of retardation effects in electronic screening and pinpoints a key challenge in functionalizing correlated materials for ultrafast device operatio

Покращення інформативності бронетанкового озброєння за рахунок використання власних розвідувально-спостережувальних засобів

Some considerations on the improvement of informatizativity of the armored vehicles armament based on the use of one’s own reconnaissance and surveillance means are outlined in the article. According to the results of various instruments’ analysis it was revealed, that radar aids have the most potential possibilities in terms of their use for reception of the given target situation and its automatic entering into tactical automated command systems, built on information-controlling systems.В статье освещены некоторые взгляды на улучшение информативности бронетанкового вооружения за счет использования собственных разведывательно-наблюдательных средств. По результатам анализа приборов различных типов выявлено, что наибольшие потенциальные возможности в части их использования для получения данных целевой обстановки и автоматического ввода ее в автоматизированные системы управления тактического звена, построенных на информационно-управляющих системах, имеют радиолокационные средства.У статті висвітлені деякі погляди на покращення інформативності бронетанкового озброєння за рахунок використання власних розвідувально-спостережних засобів. За результатом аналізу приладів різних типів виявлено, що найбільші потенційні можливості щодо їх застосування для отримання даних цільової обстановки та автоматизованого введення її в автоматизовані системи управління тактичної ланки, побудованих на інформаційно-управляючих системах, мають радіолокаційні засоби

Charge Configuration Memory Devices: Energy Efficiency and Switching Speed

Current trends in data processing have given impetus for an intense search of new concepts of memory devices with emphasis on efficiency, speed, and scalability. A promising new approach to memory storage is based on resistance switching between charge-ordered domain states in the layered dichalcogenide 1T-TaS2. Here we investigate the energy efficiency scaling of such charge configuration memory (CCM) devices as a function of device size and data write time τW as well as other parameters that have bearing on efficient device operation. We find that switching energy efficiency scales approximately linearly with both quantities over multiple decades, departing from linearity only when τW approaches the ∼0.5 ps intrinsic switching limit. Compared to current state of the art memory devices, CCM devices are found to be much faster and significantly more energy efficient, demonstrated here with two-terminal switching using 2.2 fJ, 16 ps electrical pulses

Cardiac-specific beta-catenin deletion dysregulates energetic metabolism and mitochondrial function in perinatal cardiomyocytes

beta-Catenin signaling pathway regulates cardiomyocytes proliferation and differentiation, though its involvement in metabolic regulation of cardiomyocytes remains unknown. We used one-day-old mice with cardiac-specific knockout of beta-catenin and neonatal rat ventricular myocytes treated with beta-catenin inhibitor to investigate the role of beta-catenin metabolism regulation in perinatal cardiomyocytes. Transcriptomics of perinatal beta-cateninablated hearts revealed a dramatic shift in the expression of genes involved in metabolic processes. Further analysis indicated an inhibition of lipolysis and glycolysis in both in vitro and in vivo models. Finally, we showed that beta-catenin deficiency leads to mitochondria dysfunction via the downregulation of Sirt1/PGC-1 alpha pathway. We conclude that cardiac-specific beta-catenin ablation disrupts the energy substrate shift that is essential for postnatal heart maturation, leading to perinatal lethality of homozygous beta-catenin knockout mice