Measurement of Superconductivity and Edge States in Topological Superconductor Candidate TaSe_(3)

Topological superconductors(TSCs)have been widely investigated in recent years due to their novel physics and ability to host Majorana fermions(MFs)which are key to topological quantum computation.Despite the great interest,only a few compounds have been proposed as candidates of intrinsic TSCs,such as iron-based superconductor FeSe_(0.55)Te_(0.45) and 2M-WS_(2).Among them,quasi-one-dimensional superconductor TaSe_(3) possesses fascinating properties such as its simple stoichiometry,layered nature and chemical stability.Here,using scanning tunneling microscope/spectroscopy(STM/STS),we systematically investigate the topography and electronic structure of TaSe_(3).Our STM/STS measurement reveals large atomically flat,defect-free surfaces suitable for the search of MF;electronic density of states consistent with our angle-resolved photoemission result and band-structure calculations,and a uniform superconducting gap with a typical size of∼0.25 meV.Remarkably,additional edge states are observed in the vicinity of the terrace edge,suggesting they may have a topological origin.Our result proves the coexistence of superconductivity and topological electronic structure in TaSe_(3),making it an intriguing platform to investigate topological superconductivity.

A New Effect of Oxygen Plasma on Two-Dimensional Field-Effect Transistors:Plasma Induced Ion Gating and Synaptic Behavior

Plasma treatment is a powerful tool to tune the properties of two-dimensional materials. Previous studies have utilized various plasma treatments on two-dimensional materials. We find a new effect of plasma treatment. After controlled oxygen-plasma treatment on field-effect transistors based on two-dimensional SnSe2, the capacitive coupling between the silicon back gate and the channel through the 300 nm SiO2 dielectric can be dramatically enhanced by about two orders of magnitude(from 11 n F/cm^2 to 880 nF/cm^2), reaching good efficiency of ionliquid gating. At the same time, plasma treated devices show large hysteresis in the gate sweep demonstrating memory behavior. We reveal that this spontaneous ion gating and hysteresis are achieved with the assistance of a thin layer of water film automatically formed on the sample surface with water molecules from the ambient air, due to the change in hydrophilicity of the plasma treated samples. The water film acts as the ion liquid to couple the back gate and the channel. Thanks to the rich carrier dynamics in plasma-treated two-dimensional transistors, synaptic functions are realized to demonstrate short-and long-term memories in a single device. This work provides a new perspective on the effects of plasma treatment and a facile route for realizing neuromorphic devices.

Investigation of the room-temperature photoelectron spectroscopy of type-Ⅱ Weyl semimetal candidate WTe_(2)

Layered transition metal dichalcogenides have novel physical properties and great potential for applications.Among them,WTe2,which has an extremely large unsaturated magnetoresistance and is theoretically predicted to be a type-Ⅱ Weyl semimetal,has been extensively studied.Here,we systematically probe the electronic structure of WTe_(2) at room temperature using high-resolution angle-resolved photoelectron spectroscopy(ARPES).We find that temperature-driven chemical potential shift and Lifshitz transition,which is equivalent to low-energy band structures shift downward by around 50 meV,compared to the results at low temperatures.Our ARPES experimental results match well with previous theoretical calculations,implying the possible existence of type-Ⅱ Weyl points near the Γ-X axis.Also,as expected,there exists a dominantly electron-like Fermi surface instead of the one with compensated electrons and holes.Meanwhile,our ARPES results show that the flat band(FB) lying below the Fermi level(EF) becomes closer to the Fermi level at room temperature,which might start to dominate the transport behavior and lead to the disappearance of the unsaturated giant magnetoresistance effect.These findings not only reveal the electronic structure features of WTe_(2) at room temperature,but also provide new insights into the development of room-temperature topological quantum devices.

Itinerant to relocalized transition of felectrons in the Kondo insulator CeRu_(4)Sn_(6)

The three-dimensional electronic structure and the nature of Ce 4f electrons of the Kondo insulator CeRu_(4)Sn_(6)are investigated by angle-resolved photoemission spectroscopy,utilizing tunable photon energies.Our results reveal(i)the three-dimensional k-space nature of the Fermi surface,(ii)the localized-to-itinerant transition of f electrons occurs at a much high temperature than the hybridization gap opening temperature,and(iii)the“relocalization”of itinerant f-electrons below 25 K,which could be the precursor to the establishment of magnetic order.

Preface to the special issue on topological materials

The theoretical prediction and experimental realization of topological phases of matter open a new window for brushing up our knowledge of the band theory of materials,which has become one of the frontiers of current research.The immense research activities are not only limited to condensed matter physics,but also are expanded to high-energy physics,chemistry,materials science,and are intimately related to application fields such as quantum computing and spintronics.The topological phases of matter have been conceived as building blocks for the next-generation electronics industry,based on the concept of"topological electronics".

Global Random Attractors for the Stochastic Dissipative Zakharov Equations

The stochastic dissipative Zakharov equations with white noise are mainly investigated. The global random attractors endowed with usual topology for the stochastic dissipative Zakharov equations are obtained in the sense of usual norm. The method is to transform the stochastic equations into the corresponding partial differential equations with random coefficients by Ornstein-Uhlenbeck process. The crucial compactness of the global random attractors wiil be obtained by decomposition of solutions.