Ab Initio Comparative Study of Zincblende and Wurtzite ZnO

By employing the first-principles pseudopotential plane-wave method, the physical properties of zincblende ZnO are investigated in comparison with those of the common wurtzite structure. Zincblende ZnO is predicted to be a direct gap semiconductor. Compared to the wurtzite structure, the zincblende ZnO is characterized by smaller bandgap and pressure coefficient, larger electron effective mass, increasing static dielectric constants and more covalent bonding. Furthermore, the optical properties including dielectric function and energy loss function of zincblende ZnO were obtained and analysed with some features. These aspects reveal promising applications of zincblende ZnO in optoelectronic devices.     

Quantum Oscillations in Noncentrosymmetric Weyl Semimetal SmAlSi

As a new type of quantum state of matter hosting low energy relativistic quasiparticles, Weyl semimetals(WSMs)have attracted significant attention for scientific community and potential quantum device applications. In this study, we present a comprehensive investigation of the structural, magnetic, and transport properties of noncentrosymmetric RAl Si(R = Sm, Ce), which have been predicted to be new magnetic WSM candidates. Both samples exhibit nonsaturated magnetoresistance, with about 900% and...     

Simple One-Step Synthesis and Superconducting Properties of SmFeAsO1-xFx

The recent discovery of superconductivity in REFeAsO （RE, rare-earth metal） has generated enormous interest because these materials axe the first non-copper oxide superconductors with critical temperatures Tc exceeding 50 K as well as upper critical fields well above 100 T. However, for these new superconductors, very complicated synthesis routes, such as the complex two-step synthesis or high-pressure sintering, are required. Furthermore, there is the toxicity and volatility of arsenic to consider, sometimes a sealed quartz tube of arsenic exploded during annealing. We present a new method for producing high-temperature SmFeAsO1-xFx superconductors by using a one-step sintering process. Superconducting transition with the onset temperature of 54.6 K and high critical fields Hc2（0）≥200 T were confirmed in SmFeAsO0.7F0.3. At 5 K and at self field, critical current densities Jc estimated from the magnetization hysteresis using the whole sample size and the average particle size have reached 8.5×10^3 and 1.2×10^6 A/cm^2, respectively. Moreover, Jc exhibited a very weak dependence on magnetic field. This simple and safe one-step synthesis technique should be effective in other rare earth derivatives of iron-based superconductors.     

Pressure-Induced Superconductivity in the Charge-Density-Wave Compound LaTe2-xSbx(x=0 and 0.4)

Magnetic CeTe₂ achieving superconductivity under external pressure has received considerable attention.The intermingling of 4f and 5d electrons from Ce raised the speculation of an unconventional pairing mechanism arising from magnetic fluctuations.Here,we address this speculation using a nonmagnetic 4f-electron-free LaTe₂as an example.No structural phase transition can be observed up to 35 GPa in the in situ synchrotron diffraction patterns.Subsequent high-pressure electri...