Stability of edge magnetism against disorder in zigzag MoS2 nanoribbons

Molybdenum disulfide nanoribbons with zigzag edges show ferromagnetic and metallic properties based on previous \emph{ab-initio} calculations. The investigation of the role of disorder on the magnetic properties is, however, still lacking due to the computational costs of these methods. In this work we fill this gap by studying the magnetic and electronic properties of several nanometer long MoS$_2$ zigzag nanoribbons using tight-binding and Hubbard Hamiltonians. Our results reveal that proper tight-binding parameters for the edge atoms are crucial to obtain quantitatively the metallic states and the magnetic properties of MoS$_2$ nanoribbons. With the help of the fine-tuned parameters, we perform large-scale calculations and predict the spin domain-wall energy along the edges, which is found to be significantly lower compared to that of the zigzag graphene nanoribbons. The tight-binding approach allows us to address the effect of edge disorder on the magnetic properties. Our results open the way for investigating electron-electron effects in realistic-size nanoribbon devices in MoS$_2$ and also provide valuable information for spintronic applications.Comment: 8 pages, 7 figure

Effect of the disorder in graphene grain boundaries: A wave packet dynamics study

Chemical vapor deposition (CVD) on Cu foil is one of the most promising methods to produce graphene samples despite of introducing numerous grain boundaries into the perfect graphene lattice. A rich variety of GB structures can be realized experimentally by controlling the parameters in the CVD method. Grain boundaries contain non-hexagonal carbon rings (4, 5, 7, 8 membered rings) and vacancies in various ratios and arrangements. Using wave packet dynamic (WPD) simulations and tight-binding electronic structure calculations, we have studied the effect of the structure of GBs on the transport properties. Three model GBs with increasing disorder were created in the computer: a periodic 5-7 GB, a "serpentine" GB, and a disordered GB containing 4, 8 membered rings and vacancies. It was found that for small energies (E = EF ± 1 eV) the transmission decreases with increasing disorder. Four membered rings and vacancies are identified as the principal scattering centers. Revealing the connection between the properties of GBs and the CVD growth method may open new opportunities in the graphene based nanoelectronics. © 2013 Elsevier B.V. All rights reserved

Felsővégtag és kéz contracturáinak etiologiája, pathologiája és terápiája (Posttraumás-, ischaemiás-. Dupuytren-, perinatalis, cerebralis spasticus-, és congenitális) = Etiology, pathology and of contractures of the upper extremities and of the hand (posttraumatic, ischemic, Dupuytren's, perinatal, cerebral, spastic hand congenital)

Kutatásunkban tanulmányoztuk a különböző contracturák okait, kialakulásuk folyamatát, megelőzésük lehetőségeit, módozatait, és kialakítottuk az optimális kezelési módok protokollját. Eredményeinket, megállapításainkat a futamidő alatt rendszeresen publikáltuk, elsősorban hazai és külföldi kongresszusokon, valamint a gradualis és a postgradualis képzésben. Összesen 40 előadást (ezek egy része idézhető abstrakt formában is megjelent), 3 közleményt, és 3 könyvfejezetet publikáltunk a futamidő alatt, további 3 összefoglaló közlemény készül az elvégzett munka eredményeiről. A futamidő végén jóleső érzéssel állapítjuk meg, hogy a kutatási téma tudományos feldolgozása jó döntés volt, több szempontból is: - A változó okok miatt létrejött contracturák nagyon sok fiatal, munkaképes korosztályban lévő embert érintenek, hosszú ideig tartó betegállománnyal, többszöri műtéti kezeléssel és munkaképesség csökkenéssel. E betegségek megelőzése és korszerű kezelése magas szintű kézsebészeti ismereteket igényel. - A témavezető helyesen döntött, amikor a kutató csoportba fiatal orvosokat vont be. E kollégák a futamidő alatt 4 díjat nyertek el kongresszusi előadásaikkal, ismertséget és elismertséget szerezve önmaguknak, a kutatócsoportnak és Intézetünknek. Az Országos Tudományos Kutatási Alap fogadja hálás köszönetünket az anyagi támogatásért. | We studied the causes of various contracture types, the process of their development, possibilities and methods of prevention, and designed the protocol of optimal treatment methods. We regularly published our results and statements, primarily at congresses held in our country and abroad as well as at the gradual and postgradual training courses. We published 40 presentations, some of them also in the form of citable abstract, 3 articles, and 3 chapters in books. Moreover, 3 comprehensive publications are in the stage of preparation about the results of our completed research work. It is a pleasure for us to establish that the scientific work on the research topic proved to be a good decision from several aspects, as follows: · Contractures, caused by various factors, occur in a huge group of young people of working age, being in the sick list for long, undergoing several surgical procedures, and suffering from the decrease of working ability. Prevention and up-to-date management of these diseases require high level knowledge of hand surgery. · It proved to be a proper decision of the project coordinator that young doctors had been included into the research group. These young colleagues won 4 prices with their lectures at congresses during the research period, obtaining repute and recognition for themselves, for the research group and for our Institute. Many thanks to the National Research Foundation for the financial support

Observation of competing, correlated ground states in the flat band of rhombohedral graphite

In crystalline solids, the interactions of charge and spin can result in a variety of emergent quantum ground states, especially in partially filled, topological flat bands such as Landau levels or in “magic angle” graphene layers. Much less explored is rhombohedral graphite (RG), perhaps the simplest and structurally most perfect condensed matter system to host a flat band protected by symmetry. By scanning tunneling microscopy, we map the flat band charge density of 8, 10, 14, and 17 layers and identify a domain structure emerging from a competition between a sublattice antiferromagnetic insulator and a gapless correlated paramagnet. Our density matrix renormalization group calculations explain the observed features and demonstrate that the correlations are fundamentally different from graphene-based magnetism identified until now, forming the ground state of a quantum magnet. Our work establishes RG as a platform to study many-body interactions beyond the mean-field approach, where quantum fluctuations and entanglement dominate

Revealing the Topological Phase Diagram of ZrTe5 Using the Complex Strain Fields of Microbubbles

Topological materials host robust properties, unaffected by microscopic perturbations, owing to the global topological properties of the bulk electron system. Materials in which the topological invariant can be changed by easily tuning external parameters are especially sought after. Zirconium pentatelluride (ZrTe5) is one of a few experimentally available materials that reside close to the boundary of a topological phase transition, allowing the switching of its invariant by mechanical strain. Here, we unambiguously identify a topological insulator–metal transition as a function of strain, by a combination of ab initio calculations and direct measurements of the local charge density. Our model quantitatively describes the response to complex strain patterns found in bubbles of few layer ZrTe5 without fitting parameters, reproducing the mechanical deformation-dependent closing of the band gap observed using scanning tunneling microscopy. We calculate the topological phase diagram of ZrTe5 and identify the phase at equilibrium, enabling the design of device architectures, which exploit the topological switching characteristics of the system