1,207 research outputs found
Two energy scales and close relationship between the pseudogap and superconductivity in underdoped cuprate superconductors
By measuring the low temperature specific heat, the low energy quasi-particle
excitation has been derived and analyzed in systematically doped
LaSrCuO single crystals. The Volovik's relation predicted
for a d-wave superconductor has been well demonstrated in wide doping regime,
showing a robust evidence for the d-wave pairing symmetry. Furthermore the
nodal gap slope of the superconducting gap is derived and is found
to follow the same doping dependence of the pseudogap obtained from ARPES and
tunnelling measurement. This strongly suggests a close relationship between the
pseudogap and superconductivity. Taking the entropy conservation into account,
we argue that the ground state of the pseudogap phase should have Fermi arcs
with finite density of states at zero K, and the transport data show that it
behaves like an insulator due to probably weak localization. A nodal metal
picture for the pseudogap phase cannot interpret the data. Based on the Fermi
arc picture for the pseudogap phase it is found that the superconducting energy
scale or in underdoped regime is governed by both the maximum gap and the
spectral weight from the Fermi arcs. This suggests that there are two energy
scales: superconducting energy scale and the pseudogap. The superconductivity
may be formed by the condensation of Fermi arc quasiparticles through pairing
by exchanging virtue bosons.Comment: 4 pages, 5 figure
Synthesizing and characterization of hole doped nickel based layer superconductor (LaSr)ONiAs
We report the synthesizing and characterization of the hole doped Ni-based
superconductor (. By substituting La with Sr, the
superconducting transition temperature is increased from 2.75 K of the
parent phase to 3.7 K at the doping levels x= 0.1 - 0.2. The curve
versus hole concentration shows a symmetric behavior as the electron
doped samples . The normal state resistivity in Ni-based
samples shows a good metallic behavior and reveals the absence of an anomaly
which appears in the Fe-based system at about 150 K, suggesting that this
anomaly is not a common feature for all systems. Hall effect measurements
indicate that the electron conduction in the parent phase is
dominated by electron-like charge carriers, while with more Sr doping, a
hole-like band will emerge and finally prevail over the conduction, and
accordingly the superconducting transition temperature increases.Comment: 4 pages, 5 figure
A Mutual Attraction Model for Both Assortative and Disassortative Weighted Networks
In most networks, the connection between a pair of nodes is the result of
their mutual affinity and attachment. In this letter, we will propose a Mutual
Attraction Model to characterize weighted evolving networks. By introducing the
initial attractiveness and the general mechanism of mutual attraction
(controlled by parameter ), the model can naturally reproduce scale-free
distributions of degree, weight and strength, as found in many real systems.
Simulation results are in consistent with theoretical predictions.
Interestingly, we also obtain nontrivial clustering coefficient C and tunable
degree assortativity r, depending on and A. Our weighted model appears as
the first one that unifies the characterization of both assortative and
disassortative weighted networks.Comment: 4 pages, 3 figure
A regular black hole as the final state of evolution of a singular black hole
We propose a novel black hole model in which singular and regular black holes
are combined as a whole and more precisely singular and regular black holes are
regarded as different states of parameter evolution. We refer to them as
singular and regular states, respectively. Furthermore, the regular state is
depicted by the final state of parameter evolution in the model. We also
present the sources that can generate such a black hole spacetime in the
framework of gravity. This theory of modified gravity is adopted because
it offers a possible resolution to a tough issue in the thermodynamics of
regular black holes, namely the discrepancy between the thermal entropy and
Wald entropy. The dynamics and thermodynamics of the novel black hole model are
also discussed when a singular state evolves into a regular state during the
change of charge or horizon radius from its initial value to its extreme value.Comment: 36 pages, 23 figures, references adde
General Dynamics of Topology and Traffic on Weighted Technological Networks
For most technical networks, the interplay of dynamics, traffic and topology
is assumed crucial to their evolution. In this paper, we propose a
traffic-driven evolution model of weighted technological networks. By
introducing a general strength-coupling mechanism under which the traffic and
topology mutually interact, the model gives power-law distributions of degree,
weight and strength, as confirmed in many real networks. Particularly,
depending on a parameter W that controls the total weight growth of the system,
the nontrivial clustering coefficient C, degree assortativity coefficient r and
degree-strength correlation are all in consistence with empirical evidences.Comment: 4 pages, 4 figure
- …