Discovery of Two Families of VSb-Based Compounds with V-Kagome Lattice

We report the structure and physical properties of two newly discovered compounds AV_(8)Sb_(12)and AV_(6)Sb_(6)(A=Cs,Rb),which have C_(2)(space group:Cmmm)and C_(3)(space group:R3 m)symmetry,respectively.The basic Vkagome unit appears in both compounds,but stacking differently.AV_(2)Sb_(2) layer is sandwiched between two V_(3)Sb_(5)layers in AV_(8)Sb_(12),altering the V-kagome lattice and lowering the symmetry of kagome layer from hexagonal to orthorhombic.In AV_(6)Sb_(6),the building block is a more complex slab made up of two half-V_(3)Sb_(5)layers that are intercalated by Cs cations along the c-axis.Transport property measurements demonstrate that both compounds are nonmagnetic metals,with carrier concentrations at around 10^(21)cm^(-3).No superconductivity has been observed in CsV_(8)Sb_(12)above 0.3 K under in situ pressure up to 46 GPa.Compared to CSV_(3)Sb_(5),theoretical calculations and angle-resolved photoemission spectroscopy reveal a quasi-two-dimensional electronic structure in CsV_(8)Sb_(12)with C_(2)symmetry and no van Hove singularities near the Fermi level.Our findings will stimulate more research into V-based kagome quantum materials.

Low on-resistance 1.2 kV 4H-SiC power MOSFET with Ron, sp of 3.4 mΩ·cm^2

A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm^2 and breakdown voltage exceeding 1.5 kV is designed and fabricated.Numerical simulations are carried out to optimize the electric field strength in gate oxide and at the surface of the semiconductor material in the edge termination region.Additional n-type implantation in JFET region is implemented to reduce the specific on-resistance.The typical leakage current is less than 1μA at VDS=1.4 kV.Drain–source current reaches 50 A at VDS=0.75 V and VGS=20 V corresponding to an on-resistance of 15 mΩ.The typical gate threshold voltage is 2.6 V.

Fluctuating magnetic droplets immersed in a sea of quantum spin liquid

The search of quantum spin liquid(QSL),an exotic magnetic state with strongly fluctuating and highly entangled spins down to zero temperature,is a main theme in current condensed matter physics.However,there is no smoking gun evidence for deconfined spinons in any QSL candidate so far.The disorders and competing exchange interactions may prevent the formation of an ideal QSL state on frustrated spin lattices.Here we report comprehensive and systematic measurements of the magnetic susceptibility,ultralow-temperature specific heat,muon spin relaxation(μSR),nuclear magnetic resonance(NMR),and thermal conductivity for NaYbSe2 single crystals,in which Yb3+ions with effective spin-1/2 form a perfect triangular lattice.All these complementary techniques find no evidence of long-range magnetic order down to their respective base temperatures.Instead,specific heat,μSR,and NMR measurements suggest the coexistence of quasi-static and dynamic spins in NaYbSe2.The scattering from these quasi-static spins may cause the absence of magnetic thermal conductivity.Thus,we propose a scenario of fluctuating ferrimagnetic droplets immersed in a sea of QSL.This may be quite common on the way pursuing an ideal QSL,and provides a brand new platform to study how a QSL state survives impurities and coexists with other magnetically ordered states.

Puerarin improves diabetic wound healing via regulation of macrophage M2 polarization phenotype

Background:Skin wound healing depends on the progress of different but overlapping stages of healing,including hemostasis,inflammatory,proliferative and remodeling.Failure of these stages to occur in a timely and gradual manner may result in non-healing pathological wounds.Macrophages and neutrophils have been shown to play an essential role in the inflammatory responses of wound tissue,and their active plasticity allows them to modulate tissue damage and repair functions.The ability of macrophages and neutrophils to regulate the occurrence and resolution of inflammatory processes is essential for the treatment of pathological wound healing.Methods:Mice were categorized into negative control,streptozotocin,streptozotocin+puerarin and puerarin groups.The traditional Chinese medicine extract puerarin was selected to treat different groups of mice with a full-thickness skin defect wound.Cells of the RAW264.7 cell line were stimulated under different puerarin conditions.Then,real time quantitative polymerase chain reaction(RT-qPCR),western blot,immunofluorescence and other assays were carried out to explore the effect of puerarin on wound healing and its molecular mechanism.Results:Animal experiments found that the wound healing of diabetic mice treated with puerarin was significantly accelerated,and histological analysis found that puerarin treatment markedly decreased the infiltration of macrophages and neutrophils in wound tissue.Through western blot,RT-qPCR and immunofluorescence experiments,it was observed that puerarin treatment remarkably inhibited nuclear factor kinase B(NF-κB)and mitogen-activated protein kinase(MAPK)signaling pathways,downregulated the expression of inflammatory cytokines and induced the M2 polarization of macrophages.At the cellular level,we also observed that puerarin improved M2 macrophage polarization and inhibited inflammatory pathway activation in a high-glucose culture.Conclusion:Puerarin has a significant therapeutic effect on wound healing in diabetic mice.The therapeutic effect is achieved by regulating macrophage polarization through suppressing NF-κB and MAPK signaling cascades.

PbTaSe2拓扑表面态诱导的向列超导电性

通过平面内磁场转角的电阻和点接触谱的测量,作者发现拥有Dirac节点线的拓扑材料PbTaSe2中超导能隙存在明显的二重对称行为,低于PbTaSe2六角晶格结构的对称性,表明向列超导电性的存在.这种二重对称性会一直持续到表面超导的上临界场Hc2R,尽管体超导在体上临界场c2RH<<Hc2R以上已经被抑制.该结果表明二重对称行为起源于表面的向列超导电性.同时,在测量的精度范围内,磁场转角比热的数据也并没有观测到体超导的各向异性.值得注意的是, PbTaSe2的向列超导电性与拓扑超导候选材料CuxBi2Se3有所不同,后者的二重对称行为来自于体态超导.结合理论分析,本文认为PbTaSe2的向列超导电性可能起源于其拓扑表面态形成的拓扑超导态而不是体态超导的近邻效应,该理论预言PbTaSe2的表面超导会破坏时间反演对称.PbTaSe2的系统研究有助于进一步探索向列超导电性与拓扑超导之间的关系.

Nodeless superconducting gaps in Ca10(Pt(4-δ)As8)((Fe(1-x)Ptx)2As2)5 probed by quasiparticle heat transport

The in-plane thermal conductivity of the iron-based superconductor Ca10(Pt_(4-δ)As_8)((Fe_(1-x)Pt_x)_2As_2)_5 single crystal("10-4-8", T c= 22 K) was measured down to 80 m K. In a zero field, the residual linear term κ_0/T is negligible, suggesting the nodeless superconducting gaps in this multiband compound. In the magnetic fields, κ_0/T increases rapidly, which mimics the multiband superconductor Nb Se_2 and Lu Ni_2B_2 C with highly anisotropic gap. Such a field dependence of κ_0/T is an evidence for the multiple superconducting gaps with quite different magnitudes or highly anisotropic gap. Compared with the London penetration depth results of the Ca10(Pt_(4-δ)As_8)((Fe_(1-x)Pt_x)_2As_2)_5("10-3-8") compound, the 10-4-8 and 10-3-8 compounds may have a similar superconducting gap structure.