Intrinsic Percolative Superconductivity in Heavily Overdoped High Temperature Superconductors

Magnetic measurements on heavily overdoped $La_{2-x}Sr_xCuO_4$, $Tl_2Ba_2CuO_6$, $Bi_2Sr_2CuO_6$ and $Bi_2Sr_2CaCu_2O_8$ single crystals reveal a new type magnetization hysteresis loops characterized by the vanishing of usual central peak near zero field. Since this effect has been observed in various systems with very different structural details, it reflects probably a generic behavior for all high temperature superconductors. This easy penetration of magnetic flux can be understood in the picture of percolative superconductivity due to the inhomogeneous electronic state in heavily overdoped regime.Comment: 4 pages, 5 figure

New parametrization for the nuclear covariant energy density functional with point-coupling interaction

A new parametrization PC-PK1 for the nuclear covariant energy density functional with nonlinear point-coupling interaction is proposed by fitting to observables for 60 selected spherical nuclei, including the binding energies, charge radii and empirical pairing gaps. The success of PC-PK1 is illustrated in its description for infinite nuclear matter and finite nuclei including the ground-state and low-lying excited states. Particularly, PC-PK1 improves the description for isospin dependence of binding energy along either the isotopic or the isotonic chains, which makes it more reliable for application in exotic nuclei. The predictive power of PC-PK1 is also illustrated for the nuclear low-lying excitation states in a five-dimensional collective Hamiltonian in which the parameters are determined by constrained calculations for triaxial shapes.Comment: 32 pages, 12 figures, 4 tables, accepted by Phys. Rev.

Unified theory of PT and CP invariant topological metals and nodal superconductors

As PT and CP symmetries are fundamental in physics, we establish a unified topological theory of PT and CP invariant metals and nodal superconductors, based on the mathematically rigorous $KO$ theory. Representative models are constructed for all nontrivial topological cases in dimensions $d=1,2$, and $3$, with their exotic physical meanings being elucidated in detail. Intriguingly, it is found that the topological charges of Fermi surfaces in the bulk determine an exotic direction-dependent distribution of topological subgap modes on the boundaries. Furthermore, by constructing an exact bulk-boundary correspondence, we show that the topological Fermi points of the PT and CP invariant classes can appear as gapless modes on the boundary of topological insulators with a certain type of anisotropic crystalline symmetry.Comment: 4 pages, 1 figure and supplemental material, to be published in PR

Coherent lidar signal fluctuation reduction by means of frequency diversity technique

The atmospheric return measured by a coherent lidar is typically characterized by rapid and deep fluctuations in signal strength. These fluctuations result from the interference of the fields backscattered to the lidar from randomly located aerosol particles which move relative to the lidar pulse. In many applications, it is necessary to determine the average value of the lidar signal intensity at some range. A new method utilizes frequency diversity initially suggested by Goldstein and subsequently studied in the microwave radar domain by others. It is expected that the application of the frequency diversity method in the coherent lidar domain will eventually provide greater efficiency and speed in the return signal averaging needed to obtain accurate intensity estimates. The frequency diversity method recognizes that the transmitted lidar pulse is very long compared to a wavelength and consequently a given phase, theta sub i, is repeated many times within the pulse. In order to test this concept, a fairly simple laboratory experiment was designed which simulates scattering of a lidar pulse from atmospheric aerosol. The testing of the frequency diversity method is discussed

Periodic ripples in suspended graphene

We study the mechanism of wrinkling of suspended graphene, by means of atomistic simulations. We argue that the structural instability under edge compression is the essential physical reason for the formation of periodic ripples in graphene. The ripple wavelength and out-of-plane amplitude are found to obey 1/4-power scaling laws with respect to edge compression. Our results also show that parallel displacement of the clamped boundaries can induce periodic ripples, with oscillation amplitude roughly proportional to the 1/4 power of edge displacement. The results are fundamental to graphene's applications in electronics.Comment: 5 Figure

Antimagnetic Rotation Band in Nuclei: A Microscopic Description

Covariant density functional theory and the tilted axis cranking method are used to investigate antimagnetic rotation (AMR) in nuclei for the first time in a fully self-consistent and microscopic way. The experimental spectrum as well as the B(E2) values of the recently observed AMR band in 105Cd are reproduced very well. This gives a further strong hint that AMR is realized in specific bands in nuclei.Comment: 10 pages, 4 figure

Parsec-scale jet properties of the gamma-ray quasar 3C 286

The quasar 3C~286 is one of two compact steep spectrum sources detected by the {\it Fermi}/LAT. Here, we investigate the radio properties of the parsec(pc)-scale jet and its (possible) association with the $\gamma$-ray emission in 3C~286. The Very Long Baseline Interferometry (VLBI) images at various frequencies reveal a one-sided core--jet structure extending to the southwest at a projected distance of $\sim$1 kpc. The component at the jet base showing an inverted spectrum is identified as the core, with a mean brightness temperature of $2.8\times 10^{9}$~K. The jet bends at about 600 pc (in projection) away from the core, from a position angle of $-135^\circ$ to $-115^\circ$. Based on the available VLBI data, we inferred the proper motion speed of the inner jet as $0.013 \pm 0.011$ mas yr$^{-1}$ ($\beta_{\rm app} = 0.6 \pm 0.5$), corresponding to a jet speed of about $0.5\,c$ at an inclination angle of $48^\circ$ between the jet and the line of sight of the observer. The brightness temperature, jet speed and Lorentz factor are much lower than those of $\gamma$-ray-emitting blazars, implying that the pc-scale jet in 3C~286 is mildly relativistic. Unlike blazars in which $\gamma$-ray emission is in general thought to originate from the beamed innermost jet, the location and mechanism of $\gamma$-ray emission in 3C~286 may be different as indicated by the current radio data. Multi-band spectrum fitting may offer a complementary diagnostic clue of the $\gamma$-ray production mechanism in this source.Comment: 9 pages, 4 figures, accept for publication in MNRA

Analytical considerations of flow boiling heat transfer in metal-foam filled tubes

Flow boiling in metal-foam filled tube was analytically investigated based on a modified microstructure model, an original boiling heat transfer model and fin analysis for metal foams. Microstructure model of metal foams was established, by which fiber diameter and surface area density were precisely predicted. The heat transfer model for flow boiling in metal foams was based on annular pattern, in which two phase fluid was composed by vapor region in the center of the tube and liquid region near the wall. However, it was assumed that nucleate boiling performed only in the liquid region. Fin analysis and heat transfer network for metal foams were integrated to obtain the convective heat transfer coefficient at interface. The analytical solution was verified by its good agreement with experimental data. The parametric study on heat transfer coefficient and boiling mechanism was also carried out