Tip induced unconventional superconductivity on Weyl semimetal TaAs

Weyl fermion is a massless Dirac fermion with definite chirality, which has been long pursued since 1929. Though it has not been observed as a fundamental particle in nature, Weyl fermion can be realized as low-energy excitation around Weyl point in Weyl semimetal, which possesses Weyl fermion cones in the bulk and nontrivial Fermi arc states on the surface. As a firstly discovered Weyl semimetal, TaAs crystal possesses 12 pairs of Weyl points in the momentum space, which are topologically protected against small perturbations. Here, we report for the first time the tip induced superconductivity on TaAs crystal by point contact spectroscopy. A conductance plateau and sharp double dips are observed in the point contact spectra, indicating p-wave like unconventional superconductivity. Furthermore, the zero bias conductance peak in low temperature regime is detected, suggesting potentially the existence of Majorana zero modes. The experimentally observed tunneling spectra can be interpreted with a novel mirror-symmetry protected topological superconductor induced in TaAs, which can exhibit zero bias and double finite bias peaks, and double conductance dips in the measurements. Our work can open a broad avenue in search for new topological superconducting phases from topological Weyl materials and trigger intensive investigations for pursuing Majorana fermions

Stopping power and energy loss for protons in Be plasmas

Stopping power (SP) for ions in plasmas is a basic and old problem, which data is important for heavy ion driven inertial fusion and heavy ion transport in hot matters. So far there are some relevant experiments and many theoretical researches..

Stopping power and energy loss for protons in Be plasmas

Stopping power (SP) for ions in plasmas is a basic and old problem, which data is important for heavy ion driven inertial fusion and heavy ion transport in hot matters. So far there are some relevant experiments and many theoretical researches..

Quick pseudo-random topology optimization design based on triangle element

This paper focuses on the fast highly approximate modal analysis and its applications in topology optimization design based on the triangle finite element. The proposed modal analysis methods are based on the initialized pseudo-random number vectors with the Rayleigh-Ritz analysis, which is very simple to implement and can easily be extended for structural dynamic topology optimization design. The numerical examples show that the proposed method is very effective with small computational cost and high efficiency which can effectively reduce huge computational cost without affecting the outcome of the optimization process. Meanwhile, the introduction of pseudo-random approximate modal analysis leads to the randomness and sub-optimal multiplicity of topology optimization results. Numerical examples show that the approximate pseudo-random modal analysis could also enlarge the search ability of the Optimality Criterion Method (OCM)

Filament L1482 in the California molecular cloud

Aims. The process of gravitational fragmentation in the L1482 molecular filament of the California molecular cloud is studied by combining several complementary observations and physical estimates. We investigate the kinematic and dynamical states of this molecular filament and physical properties of several dozens of dense molecular clumps embedded therein. Methods. We present and compare molecular line emission observations of the J=2--1 and J=3--2 transitions of 12CO in this molecular complex, using the KOSMA 3-meter telescope. These observations are complemented with archival data observations and analyses of the 13CO J=1--0 emission obtained at the Purple Mountain Observatory 13.7-meter radio telescope at Delingha Station in QingHai Province of west China, as well as infrared emission maps from the Herschel Space Telescope online archive, obtained with the SPIRE and PACS cameras. Comparison of these complementary datasets allow for a comprehensive multi-wavelength analysis of the L1482 molecular filament. Results. We have identified 23 clumps along the molecular filament L1482 in the California molecular cloud. All these molecular clumps show supersonic non-thermal gas motions. While surprisingly similar in mass and size to the much better known Orion molecular cloud, the formation rate of high-mass stars appears to be suppressed in the California molecular cloud relative to that in the Orion molecular cloud based on the mass-radius threshold derived from the static Bonnor Ebert sphere. Our analysis suggests that these molecular filaments are thermally supercritical and molecular clumps may form by gravitational fragmentation along the filament. Instead of being static, these molecular clumps are most likely in processes of dynamic evolution.Comment: 10 pages, 9 figures, 2 tables, accepted to Astronomy and Astrophysic