1,125 research outputs found
Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
We present a combined experimental and theoretical study of monolayer vanadium ditelluride, VTe2, grown on highly oriented pyrolytic graphite by molecular-beam epitaxy. Using various in situ microscopic and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, together with theoretical analysis by density functional theory calculations, we demonstrate direct evidence of the metallic 1T phase and 3d1 electronic configuration in monolayer VTe2 that also features a (4 × 4) charge density wave order at low temperatures. In contrast to previous theoretical predictions, our element-specific characterization by X-ray magnetic circular dichroism rules out a ferromagnetic order intrinsic to the monolayer. Our findings provide essential knowledge necessary for understanding this interesting yet less explored metallic monolayer in the emerging family of van der Waals magnets
Correction to Metallic 1T Phase, 3d1 Electronic Configuration and Charge Density Wave Order in Molecular-Beam Epitaxy Grown Monolayer Vanadium Ditelluride.
It has been brought to our attention that a mistake exists in the author list. The author “Johnson Goh” in the original article should be “Kuan Eng Johnson Goh”. His primary corresponding email is [email protected]
Survey on operating reserve procurement and pricing in deregulated electricity market environment
2003-2004 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Procurement and pricing of operating reserves based on the Peak-Load Pricing Theory
2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
Fjords as Aquatic Critical Zones (ACZs)
In recent decades, the land-ocean aquatic continuum, commonly defined as the interface, or transition zone, between terrestrial ecosystems and the open ocean, has undergone dramatic changes. On-going work has stressed the importance of treating Aquatic Critical Zones (ACZs) as a sensitive system needing intensive investigation. Here, we discuss fjords as an ACZ in the context of sedimentological, geochemical, and climatic impacts. These diverse physical features of fjords are key in controlling the sources, transport, and burial of organic matter in the modern era and over the Holocene. High sediment accumulation rates in fjord sediments allow for high-resolution records of past climate and environmental change where multiple proxies can be applied to fjord sediments that focus on either marine or terrestrial-derived components.
Humans through land-use change and climatic stressors are having an impact on the larger carbon stores in fjords. Sediment delivery whether from accelerating erosion (e.g. mining, deforestation, road building, agriculture) or from sequestration of fluvial sediment behind dams has been seriously altered in the Anthropocene. Climate change affecting rainfall and river discharge into fjords will impact the thickness and extent of the low-salinity layer in the upper reaches of the fjord, slowing the rate of the overturning circulation and deep-water renewal – thereby impacting bottom water oxygen concentrations
A shadowing problem in the detection of overlapping communities: lifting the resolution limit through a cascading procedure
Community detection is the process of assigning nodes and links in
significant communities (e.g. clusters, function modules) and its development
has led to a better understanding of complex networks. When applied to sizable
networks, we argue that most detection algorithms correctly identify prominent
communities, but fail to do so across multiple scales. As a result, a
significant fraction of the network is left uncharted. We show that this
problem stems from larger or denser communities overshadowing smaller or
sparser ones, and that this effect accounts for most of the undetected
communities and unassigned links. We propose a generic cascading approach to
community detection that circumvents the problem. Using real and artificial
network datasets with three widely used community detection algorithms, we show
how a simple cascading procedure allows for the detection of the missing
communities. This work highlights a new detection limit of community structure,
and we hope that our approach can inspire better community detection
algorithms.Comment: 14 pages, 12 figures + supporting information (5 pages, 6 tables, 3
figures
Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+x
The nature of the pseudogap state, observed above the superconducting
transition temperature TC in many high temperature superconductors, is the
center of much debate. Recently, this discussion has focused on the number of
energy gaps in these materials. Some experiments indicate a single energy gap,
implying that the pseudogap is a precursor state. Others indicate two,
suggesting that it is a competing or coexisting phase. Here we report on
temperature dependent scanning tunneling spectroscopy of Pb-Bi2Sr2CuO6+x. We
have found a new, narrow, homogeneous gap that vanishes near TC, superimposed
on the typically observed, inhomogeneous, broad gap, which is only weakly
temperature dependent. These results not only support the two gap picture, but
also explain previously troubling differences between scanning tunneling
microscopy and other experimental measurements.Comment: 6 page
Scaling, renormalization and statistical conservation laws in the Kraichnan model of turbulent advection
We present a systematic way to compute the scaling exponents of the structure
functions of the Kraichnan model of turbulent advection in a series of powers
of , adimensional coupling constant measuring the degree of roughness of
the advecting velocity field. We also investigate the relation between standard
and renormalization group improved perturbation theory. The aim is to shed
light on the relation between renormalization group methods and the statistical
conservation laws of the Kraichnan model, also known as zero modes.Comment: Latex (11pt) 43 pages, 22 figures (Feynman diagrams). The reader
interested in the technical details of the calculations presented in the
paper may want to visit:
http://www.math.helsinki.fi/mathphys/paolo_files/passive_scalar/passcal.htm
Quasi-particle interference and superconducting gap in a high-temperature superconductor Ca2-xNaxCuO2Cl2
High-transition-temperature (high-Tc) superconductivity is ubiquitous in the
cuprates containing CuO2 planes but each cuprate has its own character. The
study of the material dependence of the d-wave superconducting gap (SG) should
provide important insights into the mechanism of high-Tc. However, because of
the 'pseudogap' phenomenon, it is often unclear whether the energy gaps
observed by spectroscopic techniques really represent the SG. Here, we report
spectroscopic imaging scanning tunneling microscopy (SI-STM) studies of
nearly-optimally-doped Ca2-xNaxCuO2Cl2 (Na-CCOC) with Tc = 25 ~ 28 K. They
enable us to observe the quasi-particle interference (QPI) effect in this
material, through which unambiguous new information on the SG is obtained. The
analysis of QPI in Na-CCOC reveals that the SG dispersion near the gap node is
almost identical to that of Bi2Sr2CaCu2Oy (Bi2212) at the same doping level,
while Tc of Bi2212 is 3 times higher than that of Na-CCOC. We also find that SG
in Na-CCOC is confined in narrower energy and momentum ranges than Bi2212. This
explains at least in part the remarkable material dependence of TcComment: 13pages, 4fig
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