1,721,009 research outputs found
Quenching the Kitaev honeycomb model
No full textI studied the non-equilibrium response of an initial Néel state under time evolution with the Kitaev honeycomb model. With isotropic interactions (Jx=Jy=Jz) the system quickly loses its antiferromagnetic order and crosses over into a steady state valence bond solid, which can be inferred from the long-range dimer correlations. There is no signature of a dynamical phase transition. Upon including anisotropy (Jx=Jy≠Jz), an exponentially long prethermal regime appears with persistent magnetization oscillations whose period derives from an effective toric code
Scaling theory of few-particle delocalization
No full textWe develop a scaling theory of interaction-induced delocalization of few-particle states in disordered quantum systems. In the absence of interactions, all single-particle states are localized in d<3, while in d≥3 there is a critical disorder below which states are delocalized. We hypothesize that such a delocalization transition occurs for n-particle bound states in d dimensions when d+n≥4. Exact calculations of disorder-averaged n-particle Green's functions support our hypothesis. In particular, we show that three-particle states in d=1 with nearest-neighbor repulsion will delocalize with Wc≈1.4t and with localization length critical exponent ν=1.5±0.3. The delocalization transition can be understood by means of a mapping onto a noninteracting problem with symplectic symmetry. We discuss the importance of this result for many-body delocalization, and how few-body delocalization can be probed in cold atom experiments.</p
Spin-Orbit Coupling in Transition Metal Dichalcogenide Heterobilayer Flat Bands
Full text linkThe valence flat bands in transition metal dichalcogenide (TMD)
heterobilayers are shown to exhibit strong intralayer spin-orbit coupling. This
is reflected in a simple tight-binding model with spin-dependent complex
hoppings based on the continuum model. A perpendicular electric field causes
interlayer hybridization, such that the effective model is equivalent to the
Kane-Mele model of topological insulators. The proposed model can be used as a
starting point to understand interactions and the experimentally observed
topological phases.Comment: 5 pages, 4 figure
Tower of states and the entanglement spectrum in a coplanar antiferromagnet
No full textWe extend the analytical arguments of Metlitski and Grover (arXiv:1112.5166) to compute the entanglement spectrum and entanglement entropy of coplanar antiferromagnets with SO(3)
order parameter symmetry. The low-energy states in the entanglement spectrum exhibit the tower of states structure, as is expected for systems that undergo spontaneous symmetry breaking. Our results are consistent with numerical results on the triangular and Kagomé lattice.</p
A Practical Introduction to Density Functional Theory
No full textThese lecture notes contain a brief practical introduction to doing density functional theory calculations for crystals using the open source Quantum Espresso software. The level is aimed at graduate students who are studying condensed matter or solid state physics, either theoretical or experimental
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Exact ground state of the Lieb-Mattis Hamiltonian as a superposition of Néel states
No full textWe show that the exact ground state of the Lieb-Mattis Hamiltonian is an equal-weight superposition of all possible classical Néel states, and provide an exact formulation of this superposition in the z-spin basis for both S=1/2 and general S using Schwinger bosons. In general, a superposition of possible rotations on a general initial state is symmetric if and only if the initial state has a nonzero overlap with a singlet state and is otherwise made up of states that vanish due to the symmetrization. Most notably, |s,m=0⟩ states will vanish if symmetrized, which explains how a superposition of Néel states projects onto its singlet component
Variations on the Author
Full text link“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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