266 research outputs found
Distinct Fermi Surface Topology and Nodeless Superconducting Gap in (Tl0.58Rb0.42)Fe1.72Se2 Superconductor
High resolution angle-resolved photoemission measurements have been carried
out to study the electronic structure and superconducting gap of the
(TlRb)FeSe superconductor with a T=32 K. The
Fermi surface topology consists of two electron-like Fermi surface sheets
around point which is distinct from that in all other iron-based
compounds reported so far. The Fermi surface around the M point shows a nearly
isotropic superconducting gap of 12 meV. The large Fermi surface near the
point also shows a nearly isotropic superconducting gap of 15
meV while no superconducting gap opening is clearly observed for the inner tiny
Fermi surface. Our observed new Fermi surface topology and its associated
superconducting gap will provide key insights and constraints in understanding
superconductivity mechanism in the iron-based superconductors.Comment: 4 pages, 4 figure
Tunable Dirac Fermion Dynamics in Topological Insulators
Three-dimensional topological insulators are characterized by insulating bulk
state and metallic surface state involving Dirac fermions that behave as
massless relativistic particles. These Dirac fermions are responsible for
achieving a number of novel and exotic quantum phenomena in the topological
insulators and for their potential applications in spintronics and quantum
computations. It is thus essential to understand the electron dynamics of the
Dirac fermions, i.e., how they interact with other electrons, phonons and
disorders. Here we report super-high resolution angle-resolved photoemission
studies on the Dirac fermion dynamics in the prototypical Bi2(Te,Se)3
topological insulators. We have directly revealed signatures of the
electron-phonon coupling in these topological insulators and found that the
electron-disorder interaction is the dominant factor in the scattering process.
The Dirac fermion dynamics in Bi2(Te3-xSex) topological insulators can be tuned
by varying the composition, x, or by controlling the charge carriers. Our
findings provide crucial information in understanding the electron dynamics of
the Dirac fermions in topological insulators and in engineering their surface
state for fundamental studies and potential applications.Comment: 14 Pages, 4 Figure
Extraction of Electron Self-Energy and Gap Function in the Superconducting State of Bi_2Sr_2CaCu_2O_8 Superconductor via Laser-Based Angle-Resolved Photoemission
Super-high resolution laser-based angle-resolved photoemission measurements
have been performed on a high temperature superconductor Bi_2Sr_2CaCu_2O_8. The
band back-bending characteristic of the Bogoliubov-like quasiparticle
dispersion is clearly revealed at low temperature in the superconducting state.
This makes it possible for the first time to experimentally extract the complex
electron self-energy and the complex gap function in the superconducting state.
The resultant electron self-energy and gap function exhibit features at ~54 meV
and ~40 meV, in addition to the superconducting gap-induced structure at lower
binding energy and a broad featureless structure at higher binding energy.
These information will provide key insight and constraints on the origin of
electron pairing in high temperature superconductors.Comment: 4 pages, 4 figure
High pressure study on LaFeAsO with different Tc
We report studies on pressure dependence of superconducting transition
temperature (Tc) of LaFeAsO, LaFeAs(O0.5F0.5) and LaFeAs(O0.89F0.11) samples.
In-situ resistance measurements under high pressure showed that the Tc of these
three compounds increases with pressure initially, reaches a maximum value and
then decreases with further increasing pressure, although the Tc at ambient
pressure are different. The onset Tc of LaFeAsO is ~50 K at 1.5 GPa, which is
the highest record in La-based oxypnicited system. The significant change in Tc
induced by pressure is attributed to the orbital degeneracy and the electron
density of state at the Fermi level.Comment: 13 pages, 4 figure
Fandom and Coercive Empowerment: The commissioned production of Chinese online literature
This article examines how the relationship between consumers and producers of cultural products is shaped by the proprietary nature of digital platforms. Drawing on 4 years of online observation and analysis, we examine the relationship between the producers of online Chinese fiction, amateur writers, and their consumers, that is, the fan communities of readers who respond to their work. Enabled by Chinese literary websites, readers act like sponsors who provide emotional and financial incentives for writers to produce online fictions by commenting, voting, and sending money. Readers become actively involved not just because of the content of the stories but because they form strong commitments to stories and their writers, and gain reciprocity and a sense of self-determination during the interactional process. We argue that although writers are freer from state control online, they are still beholden to the whims of their fans because of what we call the commissioned production of fictions. We contribute to fan community studies by analyzing how commercialized website settings structure the strategies available to participants, how these settings affect the content of the cultural products, and how the Chinese historical and cultural contexts impact the dynamics of the online community.postprin
Using a community based survey of healthcare seeking behavior to estimate the actual magnitude of influenza among adults in Beijing during 2013-2014 season
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