Observation of Zero-Energy Modes with Possible Time-Reversal Symmetry Breaking on Step Edge of CaKFe_(4)As_(4)

Topologically nontrivial Fe-based superconductors attract extensive attentions due to their ability of hosting Majorana zero modes(MZMs)which could be used for topological quantum computation.Topological defects such as vortex lines are required to generate MZMs.Here,we observe the robust edge states along the surface steps of CaKFe_(4)As_(4).Remarkably,the tunneling spectra show a sharp zero-bias peak(ZBP)with multiple integerquantized states at the step edge under zero magnetic field.We propose that the increasing hole doping around step edges may drive the local superconductivity into a state with possible spontaneous time-reversal symmetry breaking.Consequently,the ZBP can be interpreted as an MZM in an effective vortex in the superconducting topological surface state by proximity to the center of a tri-junction with different superconducting order parameters.Our results provide new insights into the interplay between topology and unconventional superconductivity,and pave a new path to generate MZMs without magnetic field.

Towards better entity linking

As one of the most important components in knowledge graph construction,entity linking has been drawing more and more attention in the last decade.In this paper,we propose two improvements towards better entity linking.On one hand,we propose a simple but effective coarse-to-fine unsupervised knowledge base(KB)extraction approach to improve the quality of KB,through which we can conduct entity linking more efficiently.On the other hand,we propose a highway network framework to bridge key words and sequential information captured with a self-attention mechanism to better represent both local and global information.Detailed experimentation on six public entity linking datasets verifies the great effectiveness of both our approaches.

Reversible switching of Kondo resonance in a single-molecule junction

The control of the Kondo effect is of great interest in single-molecule junction due to its potential applications in spin based electronics.Here,we demonstrate that the Kondo effect is reversibly switched on and off in an iron phthalocyanine(FePc)single-molecule junction by using a superconducting Nb tip.In a scanning tunneling microscope-based Nb-insulator-FePc-Au junction,we achieve a reversible switching between the Kondo dip and inelastic electronic tunneling spectra by simply adjusting the tip-sample distance to tune the tunnel coupling at low temperature.Further approaching the tip leads to the picking up of the molecule to the tip apex,which transfers the geometry of the single-molecule junction into a Nb-FePc-insulator-Au type.As the molecule forms an effective magnetic impurity embedded into the superconducting ground states of the Nb tip,the out-gap Kondo dip switched to an in-gap Yu-Shiba-Rusinov state.Our results open up a new route for manipulating the Kondo effect within a single-molecule junction.

The As-surface of an iron-based superconductor CaKFe_(4)As_(4)

As a new type of iron-based superconductor, CaKFe_(4)As_(4) has recently been demonstrated to be a promising platform for observing Majorana zero modes (MZMs). The surface of CaKFe_(4)As_(4) plays an important role in realizing the MZM since it hosts superconducting topological surface states. However, due to the complicated crystal structure, the terminal surface of CaKFe_(4)As_(4) has not been determined yet. Here, by using scanning tunneling microscopy/spectroscopy (STM/S), we find that there are two types of surface structure in CaKFe_(4)As_(4). Bias-dependent atomic resolution images show an evolvement from 2–√×2–√ superstructure with respect to the As lattice into 1 × 1 when the tip is brought close to the surface, revealing the sublattice of missing As atoms. Together with the first-principles calculations, we show that the surface As layer has a buckled structure. Our findings provide insight to future surface study of CaKFe_(4)As_(4) as well as other iron-pnictide superconductors.

How the iPhone Widens the U.S.Trade Deficit with China:The Case of the iPhone X

Through an examination of the case of the iPhone X,this paper demonstrates that Chinese companies involved in the production of the iPhone X have moved up along the global value chain.According to the bill of materials,those companies contributed 25.4%of the value added of the iPhone X.About 45%of the value added of the iPhone X originated in Japan,South Korea,and other economies.The iPhone trade remains a significant element of the statistical distortion of the China-US bilateral trade imbalance.In terms of gross value,the import of one iPhone X results in a USD332.75 trade deficit for the US;measured in terms oLthe value added,however the deficit is a mere USD 104.The depreciation of the Chinese yuan(CNY)has very limited power to counterbalance the tariffs imposed by the Trump administration because the foreign value added embedded in Chinese exports is 33.9%on average.Simulation results show that to counterbalance a 25%tariff,the CNY would have to depreciate by 43.3%against the US dollar on average,and to fully compensate for a 25%tariff burden on the iPhone X,a 400%depreciation of the CNY would be necessary.Hedging the risk of the punitive U.S.tariffs by depreciating the CNY is impossible.

Sulfation of the extracellular polysaccharide from the edible fungus Stropharia rugosoannulata with its antioxidant activity

An acidic extracellular polysaccharide(EPS)was gained from Stropharia rugosoannulata fermentation broth by the alcohol precipitate method.Sulfated derivative of EPS(S-EPS)was gained by chlorosulfonic acid-pyridine method and the conditions were as follows:pyridine as the reaction solvent,temperature 80°C,and reaction time 90 min.The chemical structure and chain conformation of EPS and S-EPS were characterized by FT-IR,NMR and size exclusion chromatography(SEC)coupled with multi-angle laser light scattering(MALLS)detection.FT-IR spectra indicated the sulfated group was linked to the polymer.The EPS mainly consists of mannose,glucose and glucuronic acid,and the glycosidic bond type is mainly(1→4)-linked and(1→6)-linked.C6 and C2 were substituted by sulfate groups.The EPS was degraded into smaller molecular weight(Mw)polysaccharides with the larger molecular size(Rg)after sulfation and S-EPS has better hydrophilicity.Moreover,the sulfated derivative S-EPS was found to have a better scavenging ability on hydroxyl radicals than EPS.It proved that the chemical modification of S.rugosoannulata polysaccharides by sulfation effectively enhanced their antioxidant activity.