16,741 research outputs found
Critical behaviours of contact near phase transitions
A central quantity of importance for ultracold atoms is contact, which
measures two-body correlations at short distances in dilute systems. It appears
in universal relations among thermodynamic quantities, such as large momentum
tails, energy, and dynamic structure factors, through the renowned Tan
relations. However, a conceptual question remains open as to whether or not
contact can signify phase transitions that are insensitive to short-range
physics. Here we show that, near a continuous classical or quantum phase
transition, contact exhibits a variety of critical behaviors, including scaling
laws and critical exponents that are uniquely determined by the universality
class of the phase transition and a constant contact per particle. We also use
a prototypical exactly solvable model to demonstrate these critical behaviors
in one-dimensional strongly interacting fermions. Our work establishes an
intrinsic connection between the universality of dilute many-body systems and
universal critical phenomena near a phase transition.Comment: Final version published in Nat. Commun. 5:5140 doi:
10.1038/ncomms6140 (2014
Transport properties and anisotropy in rare earth doped CaFe2As2 single crystals with Tc above 40 K
In this paper we report the superconductivity above 40 K in the electron
doping single crystal Ca1-xRexFe2As2 (Re = La, Ce, Pr). The x-ray diffraction
patterns indicate high crystalline quality and c-axis orientation. the
resistivity anomaly in the parent compound CaFe2As2 is completely suppressed by
partial replacement of Ca by rare earth and a superconducting transition
reaches as high as 43 K, which is higher than the value in electron doping
FeAs-122 compounds by substituting Fe ions with transition metal, even
surpasses the highest values observed in hole doping systems with a transition
temperature up to 38 K. The upper critical field has been determined with the
magnetic field along ab-plane and c-axis, yielding the anisotropy of 2~3.
Hall-effect measurements indicate that the conduction in this material is
dominated by electron like charge carriers. Our results explicitly demonstrate
the feasibility of inducing superconductivity in Ca122 compounds via electron
doping using aliovalent rare earth substitution into the alkaline earth site,
which should add more ingredients to the underlying physics of the iron-based
superconductors.Comment: 21 pages, 7 figure
Topological aspect of graphene physics
Topological aspects of graphene are reviewed focusing on the massless Dirac
fermions with/without magnetic field. Doubled Dirac cones of graphene are
topologically protected by the chiral symmetry. The quantum Hall effect of the
graphene is described by the Berry connection of a manybody state by the filled
Landau levels which naturally possesses non-Abelian gauge structures. A generic
principle of the topologically non trivial states as the bulk-edge
correspondence is applied for graphene with/without magnetic field and explain
some of the characteristic boundary phenomena of graphene.Comment: 12 pages, 8 figures. Proceedings for HMF-1
Microscopic origin of local moments in a zinc-doped high- superconductor
The formation of a local moment around a zinc impurity in the high-
cuprate superconductors is studied within the framework of the bosonic
resonating-valence-bond (RVB) description of the model. A topological
origin of the local moment has been shown based on the phase string effect in
the bosonic RVB theory. It is found that such an moment distributes
near the zinc in a form of staggered magnetic moments at the copper sites. The
corresponding magnetic properties, including NMR spin relaxation rate, uniform
spin susceptibility, and dynamic spin susceptibility, etc., calculated based on
the theory, are consistent with the experimental measurements. Our work
suggests that the zinc substitution in the cuprates provide an important
experimental evidence for the RVB nature of local physics in the original (zinc
free) state.Comment: The topological reason of local moment formation is given. One figure
is adde
Some integral inequalities on time scales
In this paper, some new integral inequalities on time scales are presented by
using elementarily analytic methods in calculus of time scales.Comment: 8 page
Summer Upwelling in the Northern Continental Shelf of the South China Sea
Summer upwelling system in the northern continental shelf of the South China Sea (NCSCS) is investigated with the Pathfinder, Advanced Very High Resolution Radiometer (AVHRR) Sea Surface Temperature (SST), and a three-dimensional, baroclinic, non-linear, numerical model forced by QuikSCAT winds. The AVHRR observation and modelling results have shown the upwelling is a regular phenomenon during summer in the NCSCS. Continental shelf upwelling characteristics are clearly found in the surface and subsurface water, such as low temperature, high salinity and high potential density. They respectively locate in the east of the Hainan Island, the east of the Leizhou Peninsula and the southeast of the Zhanjiang Bay (Qiongdong Upwelling), and the inshore areas from the Shantou Coast to the Nanri Islands of Fujian Coast (Yuedong Upwelling). The centra of the upwelling are mostly located in 111°10′E、19°45′N between the Qinglan Bay and the Qizhou Archipelagoes of eastern Hainan Island, 110°15′E、18°25′N near the Lingshui Bay, 116°45′E、22°50′N of the Shantou Coast and 118°E、23°40′N near the Taiwan Shoal. It is also found that the upwelling areas and centra from modelling results are in agreement with the AVHRR SST
Strong subconvexity for self-dual -functions
In this paper, we prove strong subconvexity bounds for self-dual -functions in the -aspect and for -functions in the -spectral aspect. The bounds are strong in the sense that they are the natural limit of the moment method pioneered by Xiaoqing Li, modulo current knowledge on estimate for the second moment of -functions on the critical line
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