Room-temperature anomalous Hall effect and magnetroresistance in(Ga,Co)-codoped ZnO diluted magnetic semiconductor films

This paper reports that the （Ga, Co）-codoped ZnO thin films have been grown by inductively coupled plasma enhanced physical vapour deposition. Room-temperature ferromagnetism is observed for the as-grown thin films. The x-ray absorption fine structure characterization reveals that Co2＋ and Ga3＋ ions substitute for Zn2＋ ions in the ZnO lattice and exclude the possibility of extrinsic ferromagnetism origin. The ferromagnetic （Ga, Co）-codoped ZnO thin films exhibit carrier concentration dependent anomalous Hall effect and positive magnetoresistance at room tempera- ture. The mechanism of anomalous Hall effect and magneto-transport in ferromagnetic ZnO-based diluted magnetic semiconductors is discussed.

Electronic Structure Reconstruction across the Antiferromagnetic Transition in TaFe1.23Te3 Spin Ladder

Employing the angle-resolved photoemission spectroscopy, we study the electronic structure of TaFe1.23Te3, a two-leg spin ladder compound with a novel antiferromagnetic ground state. Quasi-two-dimensional （2D） Fermi surface is observed, with sizable inter-ladder hopping. Moreover, instead of observing an energy gap at the Fermi surface in the antiferromagnetic state, we observe the shifts of various bands. Combining these observations with density-functional-theory calculations, we propose that the large scale reconstruction of the electronic structure, caused by the interactions between the coexisting itinerant electrons and local moments, is most likely the driving force of the magnetic transition. Thus TaFe1.23Te3 serves as a simpler platform that contains similar ingredients to the parent compounds of iron-based superconductors.

Experimental Investigation of the Electronic Structure of Ca_(0.83)La_(0.17)Fe_(2)As_(2)

We performed a combined angle-resolved photoemission spectroscopy and scanning tunneling microscopy study of the electronic structure of electron-doped Ca_(0.83)La_(0.17)Fe_(2)As_(2).A surface reconstruction associated with the dimerization of As atoms is observed directly in the real space,as well as the consequent band folding in the momentum space.Besides this band folding effect,the Fermi surface topology of this material is similar to that reported previously for BaFe_(1.85)Co_(0.15)As_(2),with Γ-centered hole pockets quasi-nested to M-centered electron pockets by the antiferromagnetic wave vector.Although no superconducting gap is observed by ARPES possibly due to low superconducting volume fraction,a gap-like density of states depression of 7.7±2.9 meV is determined by scanning tunneling microscopy.

Quantization of the band at the surface of charge density wave material 2H-TaSe_(2)

By using angle-resolvea photoemission spectroscopy(ARPES) combined with the first-principies electronic structure calculations,we report the quantized states at the surface of a single crystal 2 H-TaSe_(2).We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along k_(z) direction.The quantized sub-bands shift upward towards E_(F) while the bulk band at Γ shifts downward with the decrease of temperature across charge density wave(CDW) formation.The band shifts could be intimately related to the CDW.While neither the two-dimensional Fermi-surface nesting nor purely strong electron-phonon coupling can explain the mechanism of CDW in 2 H-TaSe_(2),our experiment may ignite the interest in understanding the CDW mechanism in this family.

Observation of Strong-Coupling Pairing with Weakened Fermi-Surface Nesting at Optimal Hole Doping in Ca0.33Na0.67Fe：Asu

We report an angle-resolved photoemission investigation of optimally doped Ca0.33Na0.67Fe2As2. The Fermi surface topology of this compound is similar to that of the well-studied Ba0.6K0.4Fe2As2 material, except for larger hole pockets resulting from a higher hole concentration per Fe atoms. We find that the quasi-nesting conditions are weakened in this compound compared to Ba0.6K0.4Fe2 As2. Similar to Ba0.6K0.4Fe2As2, we observe nearly isotropie superconducting gaps with Fermi surface-dependent magnitudes for Ca0.33Na0.67 Fe2As2. A small variation in the gap size along the momentum direction perpendicular to the surface is found for one of the Fermi surfaces. Our superconducting gap results on all Fermi surface sheets fit simultaneously very well to a global gap function derived from a strong coupling approach, which contains only 2 global parameters.

Crystal structure of SARS-CoV-2 papain-like protease

The pandemic of coronavirus disease 2019(COVID-19)is changing the world like never before.This crisis is unlikely contained in the absence of effective therapeutics or vaccine.The papain-like protease(PLpro)of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)plays essential roles in virus replication and immune evasion,presenting a charming drug target.Given the PLpro proteases of SARS-CoV-2 and SARS-CoV share significant homology,inhibitor developed for SARS-CoV PLpro is a promising starting point of therapeutic development.In this study,we sought to provide structural frameworks for PLpro inhibitor design.We determined the unliganded structure of SARS-CoV-2 PLpro mutant C111 S,which shares many structural features of SARS-CoV PLpro.This crystal form has unique packing,high solvent content and reasonable resolution 2.5 A°,hence provides a good possibility for fragment-based screening using crystallographic approach.We characterized the protease activity of PLpro in cleaving synthetic peptide harboring nsp2/nsp3 juncture.We demonstrate that a potent SARS-CoV PLpro inhibitor GRL0617 is highly effective in inhibiting protease activity of SARSCoV-2 with the IC50 of 2.2?0.3 mmol/L.We then determined the structure of SARS-CoV-2 PLpro complexed by GRL0617 to 2.6 A°,showing the inhibitor accommodates the S3 e S4 pockets of the substrate binding cleft.The binding of GRL0617 induces closure of the BL2 loop and narrows the substrate binding cleft,whereas the binding of a tetrapeptide substrate enlarges the cleft.Hence,our results suggest a mechanism of GRL0617 inhibition,that GRL0617 not only occupies the substrate pockets,but also seals the entrance to the substrate binding cleft hence prevents the binding of the LXGG motif of the substrate.

笼目超导体CsV_(3)Sb_(5)中的拓扑表面态和平带的光电子谱证据

具有多种电子序和丰富物态的量子材料中往往蕴含着奇异的量子现象.不同电子序和量子态之间的相互作用也可以产生新的物理现象.本文揭示了笼目超导体CsV_(3)Sb_(5)的独特电子结构.作者在费米能附近发现了拓扑非平庸的表面态,这意味着拓扑物理很可能会参与到超导态中;同时还直接观测到了平带,这表明电子关联作用会在笼目超导体CsV_(3)Sb_(5)中起着重要的作用.这些结果表明笼目晶格CsV_(3)Sb_(5)不仅具有实现马约拉纳零模和奇异超导态的潜力,还是一个独特的可用于探索电荷密度波有序、拓扑量子态、强关联效应和超导性之间的相互作用的研究平台.

具有拓扑外尔环的电荷密度波超导体In_(x)TaSe_(2)

新型拓扑材料和拓扑相的探索是近年来凝聚态物理中的热点方向.本文发现铟插层的过渡金属硫族化合物In_(x)TaSe_(2)(112体系)具有两个外尔环,以及电荷密度波(CDW)和超导电性共存的特点.在x=0.58的样品中,发现在116和77 K温度以下具有2×√3和2×2的公度CDW,这可以被电阻率、比热和扫描隧道显微镜等测量证实.角分辨光电子能谱测量发现2×2 CCDW会打开其中一个外尔环的能隙,而另一个外尔环仍然存在,且具有理论预言的"drumhead"型表面态.另外,Tc=1 K的超导电性和低温偏离s波的临界场行为表明这个材料很可能是拓扑超导体,这为探索拓扑超导电性提供了新体系.