Search results for "insulator"
showing 10 items of 228 documents
Superconductivity near a magnetic domain wall
2018
We study the equilibrium properties of a ferromagnetic insulator/superconductor structure near a magnetic domain wall. We show how the domain wall size is affected by the superconductivity in such structures. Moreover, we calculate several physical quantities altered due to the magnetic domain wall, such as the spin current density and local density of states, as well as the resulting tunneling conductance into a structure with a magnetic domain wall.
Preparation, Characterisation and Dielectric Properties of YBa2Cu3O7-δ/ Insulator-Heterostructures
1996
YBa 2 Cu 3 O 7-δ /insulator/Au-heterostructures on SrTiO 3 or LaAlO 3 substrates were prepared to study the properties of the materials SrTiO 3 , BaTiO 3 and Ceo 2 . X-ray diffraction measurements in Bragg-Brentano geometry show c-axis-oriented growth for the superconductor and the insulators SrTiO 3 and CeO 2 . Typical values for the rocking curve width of the different insulating films are between 0.4° and 0.8°. The highest breakdown fields are measured for the insulator SrTiO 3 with +37.5 kV/mm and -8.8 kV/mm. The permittivity for CeO 2 is independent of applied field and only weakly temperature dependent. This is in contrast to the perovskite type insulators, where the permittivity depe…
Topological insulator nanoribbon Josephson junctions: Evidence for size effects in transport properties
2020
We have used Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapor Deposition to fabricate high quality Josephson junctions with Al superconducting electrodes. In our devices we observe a pronounced reduction of the Josephson critical current density $J_c$ by reducing the width of the junction, which in our case corresponds to the width of the nanoribbon. Because the topological surface states extend over the entire circumference of the nanoribbon, the superconducting transport associated to them is carried by modes on both the top and bottom surfaces of the nanoribbon. We show that the $J_c$ reduction as a function of the nanoribbons width can be accounted for by assuming that on…
Two prospective Li-based half-Heusler alloys for spintronic applications based on structural stability and spin–orbit effect
2017
To search for half-metallic materials for spintronic applications, instead of using an expensive trial-and-error experimental scheme, it is more efficient to use first-principles calculations to design materials first, and then grow them. In particular, using a priori information of the structural stability and the effect of the spin–orbit interaction (SOI) enables experimentalists to focus on favorable properties that make growing half-metals easier. We suggest that using acoustic phonon spectra is the best way to address the stability of promising half-metallic materials. Additionally, by carrying out accurate first-principles calculations, we propose two criteria for neglecting the SOI s…
High transparency Bi 2 Se 3 topological insulator nanoribbon Josephson junctions with low resistive noise properties
2019
Bi$_2$Se$_3$ nanoribbons, grown by catalyst-free Physical Vapour Deposition, have been used to fabricate high quality Josephson junctions with Al superconducting electrodes. The conductance spectra (dI/dV) of the junctions show clear dip-peak structures characteristic of multiple Andreev reflections. The temperature dependence of the dip-peak features reveals a highly transparent Al/Bi$_2$Se$_3$ topological insulator nanoribbon interface and Josephson junction barrier. This is supported by the high values of the Bi$_2$Se$_3$ induced gap and of I$_c$R$_n$ (I$_c$ critical current, R$_n$ normal resistance of the junction) product both of the order of 160 $\mu$eV, a value close to the Al gap. T…
Mixed topological semimetals driven by orbital complexity in two-dimensional ferromagnets
2018
The concepts of Weyl fermions and topological semimetals emerging in three-dimensional momentum space are extensively explored owing to the vast variety of exotic properties that they give rise to. On the other hand, very little is known about semimetallic states emerging in two-dimensional magnetic materials, which present the foundation for both present and future information technology. Here, we demonstrate that including the magnetization direction into the topological analysis allows for a natural classification of topological semimetallic states that manifest in two-dimensional ferromagnets as a result of the interplay between spin-orbit and exchange interactions. We explore the emerg…
Adaptation of gene loci to heterochromatin in the course of Drosophila evolution is associated with insulator proteins.
2020
AbstractPericentromeric heterochromatin is generally composed of repetitive DNA forming a transcriptionally repressive environment. Dozens of genes were embedded into pericentromeric heterochromatin during evolution of Drosophilidae lineage while retaining activity. However, factors that contribute to insusceptibility of gene loci to transcriptional silencing remain unknown. Here, we find that the promoter region of genes that can be embedded in both euchromatin and heterochromatin exhibits a conserved structure throughout the Drosophila phylogeny and carries motifs for binding of certain chromatin remodeling factors, including insulator proteins. Using ChIP-seq data, we demonstrate that ev…
The Sea Urchin sns5 Chromatin Insulator Shapes the Chromatin Architecture of a Lentivirus Vector Integrated in the Mammalian Genome.
2016
Lentivirus vectors are presently the favorite vehicles for therapeutic gene transfer in hematopoietic cells. Nonetheless, these vectors integrate randomly throughout the genome, exhibiting variegation of transgene expression due to the spreading of heterochromatin into the vector sequences. Moreover, the cis-regulatory elements harbored by the vector could disturb the proper transcription of resident genes neighboring the integration site. The incorporation of chromatin insulators in flanking position to the transferred unit can alleviate both the above-mentioned dangerous effects, due to the insulator-specific barrier and enhancer-blocking activities. In this study, we report the valuable …
Surface structure promoted high-yield growth and magnetotransport properties of Bi2Se3 nanoribbons
2019
AbstractIn the present work, a catalyst-free physical vapour deposition method is used to synthesize high yield of Bi2Se3 nanoribbons. By replacing standard glass or quartz substrates with aluminium covered with ultrathin porous anodized aluminium oxide (AAO), the number of synthesized nanoribbons per unit area can be increased by 20–100 times. The mechanisms of formation and yield of the nanoribbons synthesized on AAO substrates having different arrangement and size of pores are analysed and discussed. It is shown that the yield and average length of the nanoribbons can base tuned by adjustment of the synthesis parameters. Analysis of magnetotransport measurements for the individual Bi2Se3…
Transcriptomic data from panarthropods shed new light on the evolution of insulator binding proteins in insects : Insect insulator proteins.
2016
Background Body plan development in multi-cellular organisms is largely determined by homeotic genes. Expression of homeotic genes, in turn, is partially regulated by insulator binding proteins (IBPs). While only a few enhancer blocking IBPs have been identified in vertebrates, the common fruit fly Drosophila melanogaster harbors at least twelve different enhancer blocking IBPs. We screened recently compiled insect transcriptomes from the 1KITE project and genomic and transcriptomic data from public databases, aiming to trace the origin of IBPs in insects and other arthropods. Results Our study shows that the last common ancestor of insects (Hexapoda) already possessed a substantial number …