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Konfiguracijska elektronska stanja v plastovitih prehodno kovinskih dihalkogenidih
No full textMesoscopic irregularly ordered and even amorphous self-assembled electronic structures were recently reported in two-dimensional metallic dichalcogenides (TMDs), created and manipulated with short light pulses or by charge injection. Apart from promising new all-electronic memory devices, such states are of great fundamental importance, since such aperiodic states cannot be described in terms of conventional charge-density-wave (CDW) physics. In this thesis, we first address the problem of metastable mesoscopic configurational charge ordering in TMDs with a sparsely filled charged lattice gas model in which electrons are subject only to screened Coulomb repulsion. The model correctly predicts commensurate CDW states corresponding to different TMDs at magic filling fractions . Doping away from results either in multiple near degenerate configurational states, or an amorphous state at the correct density observed by scanning tunneling microscopy. Quantum fluctuations between degenerate states predict a quantum charge liquid at low temperatures, revealing a new generalized viewpoint on both regular, irregular and amorphous charge ordering in transition metal dichalcogenides.
During the development of our model we also found it useful in three other examples of experiments. The first application of the model deals with theoretical modeling of the non-equilibrium amorphous state in 1T-TaS. The second application deals with quantum billiards of correlated electrons confined in triangular transition metal dichalcogenide monolayer nanostructures created by laser quench. The third and last application of our model deals with a time-domain phase diagram of metastable states in a charge ordered quantum material. Finally, we extend our classical version of the model to the quantum regime and deploy it on D-Wave’s quantum computer. We explore the observation of quantum domain melting and its simulation with a quantum computer.Nedavne raziskave poročajo o mezoskopskih nepravilno urejenih in celo amorfnih samosestavljenih elektronskih strukturah v dvodimenzionalnih prehodno kovinskih dikalkogenidih (PKD), ustvarjenih in manipuliranih s kratkimi svetlobnimi impulzi ali z injekcijo naboja. Poleg tega, da obetajo nove vseelektronske pomnilniške naprave, so takšna stanja zelo pomembna, saj takšnih aperiodičnih stanj ni mogoče opisati s konvencionalno fiziko valov gostote naboja (VGN). V tej disertaciji najprej obravnavamo problem metastabilnega mezoskopskega konfiguracijskega urejanja naboja v PKD z modelom redkega nabitega plina na rešetki, v katerem med elektroni obstaja le senčen Coulombov odboj. Model pravilno napoveduje komenzurabilna stanja VGN, ki ustrezajo različnim PKD pri magičnih polnilih . Dopiranje stran od povzroči bodisi več skoraj degeneriranih konfiguracijskih stanj, bodisi amorfno stanje pri določenem polnilu, ki ga opazimo z vrstično tunelsko mikroskopijo. Kvantne fluktuacije med degeneriranimi stanji napovedujejo kvantno tekočino nabojev pri nizkih temperaturah, kar razkriva nov posplošen pogled na urejeno, neurejeno in amorfno ureditev naboja v prehodno kovinskih dikalkogenidih.
Med razvojem našega modela za razumevanje univerzalnih komenzurabilnih struktur VGN v PKD smo ugotovili, da je uporaben tudi pri drugih nepredvidenih aplikacijah v primeru različnih eksperimentov. V tej disertaciji predstavljamo tri tovrstne primere. Prva uporaba modela se nanaša na teoretično modeliranje neravnovesnega amorfnega stanja v 1T-TaS. Druga uporaba našega modela se nanaša na kvantni biljard koreliranih elektronov, ki so omejeni v trikotnih enoslojnih nanostrukturah prehodno kovinskega dikalkogenida, ustvarjenih z laserskimi sunki. Tretja in zadnja aplikacija našega modela se ukvarja s faznim diagramom metastabilnih stanj v kvantnem materialu z urejenim nabojem v časovni domeni. Nazadnje smo našo klasično različico modela razširili na kvantni režim in jo uporabili na kvantnem računalniku D-Wave. Raziskali smo opazovanje taljenja kvantnih domen in njegovo simulacijo s kvantnim računalnikom
Introduction to quantum computing
No full textI will give an overview of the quantum computing landscape, existing quantum hardware, quantum algorithms, quantum error correction, and the quantum internet
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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