8,850 research outputs found
Electronic correlations in topological materials
No full textThe interest in topological materials has flourished in recent years due to their topological protection of remarkable physical properties under weak perturbations, which ensures the realisation of robust exotic features in realistic materials. However, many of the theoretical achievements of topology in condensed matter, such as the landmark relationship between Hall conductance and the first Chern number discovered by Thouless, Kohmoto, Nightingale and den Nijs, inherently assume a single-particle description of the many-body wave function, so that the role of interactions and correlations in topological materials is not yet fully understood. This work aims to partially fill this gap, covering a wide range of topological phenomena induced or supported by electronic interactions.
First, the topological character of spin excitons and their condensation in quantum spin Hall insulators will be investigated, with particular emphasis on their effect on the physics of electronic chiral edge states.
Second, the joint effects of flat optical moiré phonons and Coulomb repulsion on the phase diagram of twisted bilayer graphene are studied, showing that their interplay can stabilise topological insulators and superconductors in agreement with experimental evidence.
Third, the exact role of the Green's function zeros in the topological invariants for strongly correlated systems is elucidated, showing that the zeros contribute on an equal footing with the Green's function poles. In particular, in the case of a topological Mott insulator, it is shown that the topology is carried entirely by the Green's function zeros and not by the poles, a genuine strongly correlated effect that lacks any non-interacting counterpart.
In the last part, a new explanation for the peculiar Fermi liquid properties of topological Kondo insulators is proposed, motivated by recent findings that zeros of the Green's function could directly correspond to the presence of neutral quasiparticles. In particular, a new realistic model for these strongly interacting topological insulators is introduced and then studied by means of cluster dynamical mean field calculations, confirming the presence of ingap Green's function zeros
Unified role of Green's function poles and zeros in topological insulators
No full textGreen's function zeros, which can emerge only if correlation is strong, have
been for long overlooked and believed to be devoid of any physical meaning,
unlike Green's function poles. Here, we prove that Green's function zeros
instead contribute on the same footing as poles to determine the topological
character of an insulator. The key to the proof, worked out explicitly in 2D
but easily extendable in 3D, is to express the topological invariant in terms
of a quasiparticle thermal Green's function matrix , with hermitian
, by filtering out the positive definite
quasiparticle residue. In that way, the topological invariant is easily found
to reduce to the TKNN formula for quasiparticles described by the
non-interacting Hamiltonian . Since the poles of the
quasiparticle Green's function on the real frequency
axis correspond to poles and zeros of the physical-particle Green's function
, both of them equally determine the topological
character of an insulator.Comment: 12 pages, 2 figure
Local Kekul\'e distortion turns twisted bilayer graphene into topological Mott insulators and superconductors
No full textMagic-angle twisted bilayer graphene displays at different fillings of the
four flat bands lying around the charge neutrality point a wealth of notable
phases that include magnetic Chern insulators, whose magnetization is mostly of
orbital nature, and contiguous superconducting domes. Such rich phase diagram
is here explained through the positive interplay of Coulomb repulsion and the
electron coupling to a twofold optical mode that corresponds to Kekul\`e
distortions localized into the small AA stacked regions of the moir\'e
supercells. A static distortion stabilizes, at any integer filling of the flat
bands, valence-bond insulators that carry finite Chern number away from charge
neutrality. Similarly, a dynamic distortion that resonates between the two
lattice vibrations leads to resonating-valence-bond topological insulators with
built-in chiral d-wave pairs that have finite Chern number equal to the angular
momentum, and thus are prone to turn superconducting upon doping away from
integer filling.Comment: 7 pages plus references, 5 figures. Supplementary Material can be
requested at [email protected]
Andrea Bacová
No full textAndrea Bacová focuses on research and teaching in the field of residential architecture. Her work includes systematic research on residential buildings and their urban context. She actively participates in promoting Slovak architecture and is the author of several publications and exhibitions
Quantum model for Impulsive Stimulated Raman Scattering
No full textThe interaction between ultrashort light pulses and non-absorbing materials is dominated by impulsive stimulated Raman scattering (ISRS). The description of ISRS in the context of pump&probe experiments is based on effective classical models describing the interaction between the phonon and pulsed electromagnetic fields.Here wereport a theoretical description ofISRSwhere we do not make any semi-classical approximation and we treat both photonic and phononic degrees of freedom at the quantum level. The results of the quantum model are compared with semiclassical results and validated by means of spectrally resolved pump&probe measurements on α-quartz
Viewer-, Author-, and Ownership in the Work of Andrea Zittel
No full textAndrea Zittel invites others to collapse the distinctions between artist, viewer, and collaborator by interacting with her usable works. This thesis explores the process of interacting with Zittel\u27s works, and how it affects viewer-, author- and ownership
The Lettere of Andrea Calmo: authorial artifices and historical reality
No full textopenNonostante l’edizione di Vittorio Rossi del 1888, la raccolta di "ingegnosi cheribizzi" e di "fantastiche fantasie" di Andrea Calmo è ancora avvolta da un certo mistero. L’autore, dissimulando la propria identità dietro alla “maschera” dell’umile pescatore veneziano, è stato in grado di offrire uno spaccato della cultura e della società nella Venezia cinquecentesca.
In particolare, è il quarto libro delle Lettere ad aver suscitato maggiore interesse tra gli studiosi ed i lettori: pubblicato nel 1566, a diversi anni di distanza dai primi tre, questo libro si distingue per il fatto che tutte le epistole sono indirizzate a delle donne immaginarie o realmente esistite.
In questa sede si propone, in primo luogo, uno studio della biografia del Calmo accompagnata da un’analisi del contesto storico-culturale della Venezia cinquecentesca; in secondo luogo, invece, viene proposto un commento di alcune lettere dell’ultimo libro dell’opera calmiana, che cerchi di far luce principalmente sull’aspetto linguistico e contenutistico del testo.Despite Vittorio Rossi's 1888 edition, Andrea Calmo's collection of "ingegnosi cheribizzi" and "fantastiche fantasie" is still shrouded in a certain mystery. The author, dissimulating his own identity behind the "mask" of the humble Venetian fisherman, was able to offer a cross-section of culture and society in sixteenth-century Venice.
In particular, it is the fourth book of the Letters that has aroused greater interest among scholars and readers: published in 1566, several years after the first three, this book stands out for the fact that all the epistles are addressed to women imaginary or actually existed.
Here we propose, first of all, a study of Calmo's biography accompanied by an analysis of the historical-cultural context of sixteenth-century Venice; secondly, however, a commentary on some letters from the last book of Calmo's work is proposed, which seeks to shed light mainly on the linguistic and content aspect of the text
Trusted Tales: Creating Authenticity in Literary Representations from Ex-Yugoslavia
No full textThis research deals with questions of authority and authenticity and how they are expressed, constructed, and appropriated within the Anglophone book market. It considers the body of literature written about ex-Yugoslavia since the 1990s Balkan conflicts by exiled writers from the region which has entered the international literary canon. Books’ routes from original publishers into English translation are discussed through practices of trust, one of the crucial social devices underpinning their exchange. Within these cross-cultural processes, the role of cultural brokers is crucial. Symbolic and cultural resources are specifically mobilised through their powerful author brands.
By exploring authenticity in the context of book publishing, I further look at how ideas and practices of community are employed and negotiated by writers and those who promote their books. My field is multi-sited and fluid, reflecting how different individual and national positions are enacted and performed through strategies ranging from unconscious dispositions to deliberate intentions. This research thus brings together ideas of the author as an authentic, representative voice together with exile as a position that grants them a new lease of relevancy in the post-socialist context.
Although ex-Yugoslav books occupy a ‘high end’ niche of the UK market, constrained by commercial as well as political, cultural, and institutional forces, in public discourse ideas of the ‘free market’ and ‘free speech’ are mobilised to produce various types of modernisation narratives. The (post)socialist production of literature is perceived as having to ‘evolve’ into a capitalist model: this would allow not only healthy competition and consumer choice but guarantee an individual writer ‘free speech’ as a basic human right. Therefore, the most general question this research raises is what kind of foreign literature gets translated into English, under what socio-cultural conditions and which politics of representation it serves within the project of world literature
Ms. Courtney Chartier, RWWL AUC, August 2011
No full textThis video is a conversation with Ms. Courtney Chartier. Ms. Chartier talks about her work on the "New Georgia Encyclopedia" and "Online Voter Education Project." Andrea Jackson, AUC Woodruff Library, is the interviewer
Tribute to Andrea Infuso
No full textThis special issue of Eurosurveillance is dedicated to the memory of Andrea Infuso, a dear and respected colleague and friend, who died suddenly on 20 September 2005 at the age of 44.
Andrea was actively involved in the preparation of this special issue on vaccination and tuberculosis. As EuroTB coordinator since 2000, his knowledge of and contacts with all European experts involved in tuberculosis surveillance in Europe were very valuable in conceiving this thematic issue. The Euroroundup published in this issue, European survey of BCG vaccination policies and surveillance in children, 2005, written by Andrea as first author, is a posthumous publication.</jats:p
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