Switching ferromagnetic spins by an ultrafast laser pulse: Emergence of giant optical spin-orbit torque

Faster magnetic recording technology is indispensable to massive data storage and big data sciences. {All-optical spin switching offers a possible solution}, but at present it is limited to a handful of expensive and complex rare-earth ferrimagnets. The spin switching in more abundant ferromagnets may significantly expand the scope of all-optical spin switching. Here by studying 40,000 ferromagnetic spins, we show that it is the optical spin-orbit torque that determines the course of spin switching in both ferromagnets and ferrimagnets. Spin switching occurs only if the effective spin angular momentum of each constituent in an alloy exceeds a critical value. Because of the strong exchange coupling, the spin switches much faster in ferromagnets than weakly-coupled ferrimagnets. This establishes a paradigm for all-optical spin switching. The resultant magnetic field (65 T) is so big that it will significantly reduce high current in spintronics, thus representing the beginning of photospintronics.Comment: 12 page2, 6 figures. Accepted to Europhysics Letters (2016). Extended version with the supplementary information. Contribution from Indiana State University,Europhysics Letters (2016

Impurity scattering and Friedel oscillations in mono-layer black phosphorus

We study the effect of impurity scattering effect in black phosphorurene (BP) in this work. For single impurity, we calculate impurity induced local density of states (LDOS) in momentum space numerically based on tight-binding Hamiltonian. In real space, we calculate LDOS and Friedel oscillation analytically. LDOS shows strong anisotropy in BP. Many impurities in BP are investigated using $T$-matrix approximation when the density is low. Midgap states appear in band gap with peaks in DOS. The peaks of midgap states are dependent on impurity potential. For finite positive potential, the impurity tends to bind negative charge carriers and vise versa. The infinite impurity potential problem is related to chiral symmetry in BP

Strain field of reinforced concrete under accelerated corrosion by digital image correlation technique

The strain field evolution and crack pattern of reinforced concrete attacked by accelerated corrosion have been studied using strain gauges and the digital image correlation (DIC) technique. Results show that there was good consistency between DIC and the classical strain gauges about the strain field evolution of corroding reinforced concrete. Moreover, the strain field and crack behavior of reinforced concrete could be tracked by DIC image pattern intuitively and its stress field could also be calculated by DIC quantitatively. However, the micro-deformation of reinforced concrete could be obtained by DIC because of its test accuracy. When reinforced concrete was attacked by accelerated corrosion, the tension stress was applied to the upper zone of reinforced bar, and the compressive stress was applied to its bottom zone. And the brittle crack was mainly a failure model of reinforced concrete

The impact of an insider and short-selling on bubble formation in experimental financial market

This study extends the institutional design of the existing literature focusing solely on short selling by introducing an insider who is informed of the dividend distribution and experienced outsiders who gain information via trading experience. Our findings show that introducing short selling and an insider does reduce the bubble duration and size. At the same time, volatility is significantly reduced. Furthermore, the presence of the single insider reduces the large undervaluation and overall turnover in pure short selling treatment and generates small positive bubbles. Once the outsiders gain information via trading experience, there are small positive bubbles with reduced volatility

Optimal charging strategy of electric vehicles customers in a smart electrical car park

© 2016, Institution of Engineering and Technology. All rights reserved. A smart electrical car park with electric vehicles (EVs) parking there, regarded as a short-term storage system, could minimize the costs of EV customers and improve the main grid stability simultaneously. This system, including numerous bidirectional AC/DC converters, a local energy storage unit and a monitoring room, is firstly established. As the hourly prices of electricity fluctuating with time, EV owners would like to charge energy from the main grid during the low-price periods to save money, while discharging energy to the main grid during high-price periods. In order to achieve this, an optimal charging scheme is proposed to determine the charging rate of each EV based on the fluctuation of hourly prices and requirements of customers. Thus, this charging/discharging strategy can reduce the costs for EV owners and help keep the balance of supply and demand for the main grid. A comparison between the cost of EVs customers with and without the developed smart charging/discharging strategy in this smart electrical car park is presented and analysed in Matlab with an optimization problem solver named Cplex in this study. It is demonstrated that the proposed charging/discharging strategy can not only reduce EV owner's cost but also improve the main grid stability as well