1,720,982 research outputs found
Subdimensional Topological Quantum Phases of Matter
No full textThis Dissertation concerns phases of matter with various ``subdimensional'' properties. We start with topologically ordered phases with subdimensional properties. This includes a discussion of fracton topologically ordered phases, resonating valence plaquette phases, and floating topological phases. We then move on to discuss systems with symmetries that act on subdimensional subsystems, in particular those with line-like subsystems in 2D or planar subsystems in 3D. A classification of symmetry-protected topological (SPT) phases protected by such symmetries is presented. Finally, we discuss symmetries which act on fractal dimensional subsystems and a classification of such phases
Quantum anomalous Hall effect from inverted charge transfer gap
Get PDFA general mechanism is presented by which topological physics arises in
strongly correlated systems without flat bands. Starting from a charge transfer
insulator, topology emerges when the charge transfer energy between the cation
and anion is reduced to invert the lower Hubbard band and the spin-degenerate
charge transfer band. A universal low-energy theory is developed for the
inversion of charge transfer gap in a quantum antiferromagnet. The inverted
state is found to be a quantum anomalous Hall (QAH) insulator with non-coplanar
magnetism. Interactions play two essential roles in this mechanism: producing
the insulating gap and quasiparticle bands prior to the band inversion, and
causing the change of magnetic order necessary for the QAH effect after
inversion. Our theory explains the electric field induced transition from
correlated insulator to QAH state in AB-stacked TMD bilayer MoTe/WSe
Strong planar subsystem symmetry-protected topological phases and their dual fracton orders
Get PDFWe classify subsystem symmetry-protected topological (SSPT) phases in 3 + 1 dimensions (3 + 1D) protected by planar subsystem symmetries: short-range entangled phases which are dual to long-range entangled Abelian fracton topological orders via a generalized “gauging” duality. We distinguish between weak SSPTs, which can be constructed by stacking 2 + 1D SPTs, and strong SSPTs, which cannot. We identify signatures of strong phases, and show by explicit construction that such phases exist. A classification of strong phases is presented for an arbitrary finite Abelian group. Finally, we show that fracton orders realizable via p-string condensation are dual to weak SSPTs, while those dual to strong SSPTs exhibit statistical interactions prohibiting such a realization
Artificial atoms, Wigner molecules, and emergent Kagome lattice in semiconductor moir\'e superlattices
Get PDFSemiconductor moir\'e superlattices comprise an array of artificial atoms and
provide a highly tunable platform for exploring novel electronic phases. We
introduce a theoretical framework for studying moir\'e quantum matter that
treats intra-moir\'e-atom interactions exactly and is controlled in the limit
of large moir\'e period. We reveal an abundance of new physics arising from
strong electron interactions when there are multiple electrons within a moir\'e
unit cell. In particular, at filling factor , the Coulomb interaction
within each three-electron moir\'e atom leads to a three-lobed ``Wigner
molecule''. When their size is comparable to the moir\'e period, the Wigner
molecules form an emergent Kagome lattice. Our work identifies two universal
length scales characterizing the kinetic and interaction energies in moir\'e
materials and demonstrates a rich phase diagram due to their interplay.Comment: Accepted by PRL. main 5 pages, 4 figures; supplement 12 pages, 4
figure
Theory of Half-Integer Fractional Quantum Spin Hall Insulator Edges
No full textWe study the edges of fractional quantum spin Hall insulators (FQSH) with
half-integer spin Hall conductance. These states can be viewed as symmetric
combinations of a spin-up and spin-down half-integer fractional quantum Hall
state (FQH) that are time-reversal invariant, and conserve the z-component of
spin. We consider the non-Abelian states based on the Pfaffian, anti-Pfaffian,
PH-Pfaffian, and 221 FQH, and generic Abelian FQH. For strong enough
spin-conserving interactions, we find that all the non-Abelian and Abelian
edges flow to the same fixed point that consists of a single pair of charged
counter-propagating bosonic modes. If spin-conservation is broken, the Abelian
edge can be fully gapped in a time-reversal symmetric fashion. The non-Abelian
edge with broken spin-conservation remains gapless due to time-reversal
symmetry, and can flow to a new fixed point with a helical gapless pair of
Majorana fermions. We discuss the possible relevance of our results to the
recent observation of a half-integer edge conductance in twisted MoTe2.Comment: 9 page
Spin-textured Chern bands in AB-stacked transition metal dichalcogenide bilayers
No full textWhile transition-metal dichalcogenide (TMD)–based moir ́e mate-rials have been shown to host various correlated electronicphenomena, topological states have not been experimentallyobserved until now [T. Li et al., Quantum anomalous Halleffect from intertwined moir ́e bands. arXiv [Preprint] (2021).https://arxiv.org/abs/2107.01796 (Accessed 5 July 2021)]. In thiswork, using first-principle calculations and continuum modeling,we reveal the displacement field–induced topological moir ́e bandsin AB-stacked TMD heterobilayer MoTe2/WSe2. Valley-contrastingChern bands with nontrivial spin texture are formed from inter-layer hybridization between MoTe2and WSe2bands of nominallyopposite spins. Our study establishes a recipe for creating topo-logical bands in AB-stacked TMD bilayers in general, which pro-vides a highly tunable platform for realizing quantum-spin Halland interaction-induced quantum anomalous Hall effect
Wavefunction approach to the fractional anomalous Hall crystal
Get PDFWe propose fractional anomalous Hall crystals (FAHCs) as possible ground states of strongly interacting electrons in parent bands with Berry curvature. FAHCs are exotic states of matter that spontaneously break continuous translation symmetry to form a fractional Chern insulator. We construct a unified family of variational wavefunctions that describe FAHCs and their competing states in the presence of uniform parent Berry curvature. We calculate their variational energy with Coulomb interactions semi-analytically in the thermodynamic limit. Our analysis reveals that FAHCs can be energetically favorable over both Wigner crystals and integer anomalous Hall crystals for sufficiently strong interactions or flat dispersion
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
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