Interferometric control of magnon-induced nearly perfect absorption in cavity magnonics

The perfect absorption of electromagnetic waves has promoted many applications, including photovoltaics, radar cloaking, and molecular detection. Unlike conventional methods of critical coupling that require asymmetric boundaries or coherent perfect absorption that require multiple coherent incident beams, here we demonstrate single-beam perfect absorption in an on-chip cavity magnonic device without breaking its boundary symmetry. By exploiting magnon-mediated interference between two internal channels, both reflection and transmission of our device can be suppressed to zero, resulting in magnon-induced nearly perfect absorption (MIPA). Such interference can be tuned by the strength and direction of an external magnetic field, thus showing versatile controllability. Furthermore, the same multi-channel interference responsible for MIPA also produces level attraction (LA)-like hybridization between a cavity magnon polariton mode and a cavity photon mode, demonstrating that LA-like hybridization can be surprisingly realized in a coherently coupled system.

Temperature-Dependent Asymmetry of Anisotropic Magnetoresistance in Silicon p-n Junctions

We report a large but asymmetric magnetoresistance in silicon p-n junctions, which contrasts with the fact of magnetoresistance being symmetric in magnetic metals and semiconductors. With temperature decreasing from 293 K to 100 K, the magnetoresistance sharply increases from 50% to 150% under a magnetic field of 2 T. At the same time, an asymmetric magnetoresistance, which manifests itself as a magnetoresistance voltage offset with respect to the sign of magnetic field, occurs and linearly increases with magnetoresistance. More interestingly, in contrast with other materials, the lineshape of anisotropic magnetoresistance in silicon p-n junctions significantly depends on temperature. As temperature decreases from 293 K to 100 K, the width of peak shrinks from 90° to 70°. We ascribe these novel magnetoresistance to the asymmetric geometry of the space charge region in p-n junction induced by the magnetic field. In the vicinity of the space charge region the current paths are deflected, contributing the Hall field to the asymmetric magnetoresistance. Therefore, the observed temperature-dependent asymmetry of magnetoresistance is proved to be a direct consequence of the spatial configuration evolution of space charge region with temperature.

Theoretical Prediction of Carrier Mobility in Few-Layer BC2N

An ideal semiconducting material should simultaneously hold a considerable direct band gap and a high carrier mobility. A 2D planar compound consisting of zigzag chains of C-C and B-N atoms, denoted as BC2N, would be a good candidate. It has a direct band gap of 2 eV, which can be further tuned by changing the layer number. At the same time, our first-principles calculations show that few-layer BC2N possesses a high carrier mobility. The carrier mobility of around one million sqaure centimeters per volt-second is obtained at its three-layer. As our study demonstrated, few-layer BC2N has potential applications in nanoelectronics and optoelectronics.

Seebeck rectification enabled by intrinsic thermoelectrical coupling in magnetic tunneling junctions

An intrinsic thermoelectric coupling effect in the linear response regime of magnetic tunneling junctions (MTJ) is reported. In the dc response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both dc and frequency-dependent transport measurements performed up to GHz frequencies. Our work refines previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications.

Trend of pesticide poisoning in recent decades in China

The past decade experienced a stunning change in the incidence and fatality rates of pesticide poisonings in China. A study on representative case records of pesticide poisoning in a chinese province is presented here. A three-fold increase in poisoning cases due to a lack of preventive measures was reported at the beginning of the 1980s, under the rural economic reformation. Occupational intoxication incidence was swiftly reduced within a couple of years, and further stepped down as the adequate means were taken. On the contrary, the increase in non-occupational cases declined very slowly. The fatality rate of occupational poisoning cases was kept low (around few per thousand), while the non-occupational remarkably declined from 30% to 11% thanks to the efforts of health and medical care centres. The number and fatality rate of non-occupational cases thus came to play a more and more important role. Such trend is worth our attention.