Flat Band and Z_(2)Topology of Kagome Metal CsTi_(3)Bi_(5)

The simple kagome-lattice band structure possesses Dirac cones,flat band,and saddle point with van Hove singularities in the electronic density of states,facilitating the emergence of various electronic orders.Here we report a titanium-based kagome metal CsTi_(3)Bi_(5)where titanium atoms form a kagome network,resembling its isostructural compound CsV_3Sb_5.Thermodynamic properties including the magnetization,resistance,and heat capacity reveal the conventional Fermi liquid behavior in the kagome metal CsTi_(3)Bi_(5)and no signature of superconducting or charge density wave(CDW)transition anomaly down to 85 m K.Systematic angle-resolved photoemission spectroscopy measurements reveal multiple bands crossing the Fermi level,consistent with the first-principles calculations.The flat band formed by the destructive interference of hopping in the kagome lattice is observed directly.Compared to Cs V_(3)Sb_(5),the van Hove singularities are pushed far away above the Fermi level in CsTi_(3)Bi_(5),in line with the absence of CDW.Furthermore,the first-principles calculations identify the nontrivial Z_(2)topological properties for those bands crossing the Fermi level,accompanied by several local band inversions.Our results suppose CsTi_(3)Bi_(5)as a complementary platform to explore the superconductivity and nontrivial band topology.

Erratum:Flat Band and Z_(2) Topology of Kagome Metal CsTi_(3)Bi_(5)[Chin.Phys.Lett.40,037102(2023)]

In our most recently published article,[1]an important reference[2]predicting CsTi_(3)Bi_(5) is missing and should be added,along with Ref.[3](originally Ref.[28]),to the introduction section.

A New Superconductor Parent Compound NaMn_(6)Bi_(5) with Quasi-One-Dimensional Structure and Lower Antiferromagnetic-Like Transition Temperatures

Mn-based superconductors are very rare and their superconductivity has only been reported in three-dimensional Mn P and quasi-one-dimensional KMn_(6)Bi_(5) and Rb Mn_(6)Bi_(5) with[Mn_(6)Bi_(5)]-columns under high pressures.Here we report the synthesis,magnetism,electrical resistivity,and specific heat capacity of the newly discovered quasione-dimensional Na Mn_(6)Bi_(5).Compared with other AMn_(6)Bi_(5)(A=K,Rb,and Cs),Na Mn_(6)Bi_(5) has abnormal Bi–Bi bond lengths and two antiferromagnetic-like transitions at 47.3 K and 51.8 K.Anisotropic resistivity and low-temperature non-Fermi liquid behavior are observed.Heat capacity measurement reveals that the Sommerfeld coefficient for Na Mn_(6)Bi_(5) is unusually large.Using first-principles calculations,an unusual enhancement of density of states near the Fermi level is demonstrated for Na Mn_(6)Bi_(5).The features make Na Mn_(6)Bi_(5) a more suitable platform to explore the interplay of magnetism and superconductivity.

A density-wave-like transition in the polycrystalline V_(3)Sb_(2) sample with bilayer kagome lattice

Recently,transition-metal-based kagome metals have aroused much research interest as a novel platform to explore exotic topological quantum phenomena.Here we report on the synthesis,structure,and physical properties of a bilayer kagome lattice compound V_(3)Sb_(2).The polycrystalline V_(3)Sb_(2) samples were synthesized by conventional solid-state-reaction method in a sealed quartz tube at temperatures below 850℃.Measurements of magnetic susceptibility and resistivity revealed consistently a density-wave-like transition at Tdw≈160 K with a large thermal hysteresis,even though some sample-dependent behaviors were observed presumably due to the different preparation conditions.Upon cooling through Tdw,no strong anomaly in lattice parameters and no indication of symmetry lowering were detected in powder x-ray diffraction measurements.This transition can be suppressed completely by applying hydrostatic pressures of about 1.8 GPa,around which no sign of superconductivity was observed down to 1.5 K.Specific-heat measurements revealed a relatively large Sommerfeld coefficientγ=18.5 mJ·mol^(-1)·K^(-2),confirming the metallic ground state with moderate electronic correlations.Density functional theory calculations indicate that V_(3)Sb_(2) shows a non-trivial topological crystalline property.Thus,our study makes V_(3)Sb_(2) a new candidate of metallic kagome compound to study the interplay between density-wave-order,nontrivial band topology,and possible superconductivity.

Screening Promising CsV_(3)Sb_(5)-Like Kagome Materials from Systematic First-Principles Evaluation

The Cs V_(3)Sb_(5) kagome lattice holds the promise for manifesting electron correlation,topology and superconductivity.However,by far only three Cs V_(3)Sb_(5)-like kagome materials have been experimentally spotted.We enlarge this family of materials to 1386 compounds via element species substitution,and the further screening process suggests that 28 promising candidates have superior thermodynamic stability,hence they are highly likely to be synthesizable.Moreover,these compounds possess several unique electronic structures,and can be categorized into five non-magnetic and three magnetic groups accordingly.It is our hope that this work can greatly expand the viable phase space of the Cs V_(3)Sb_(5)-like materials for investigating or tuning the novel quantum phenomena in kagome lattice.

准一维Mn基超导材料研究进展

探索新的高温超导材料与揭示非常规超导机理一直是凝聚态物理研究的重点.除了铜氧化物超导体和铁基超导体这两大家族之外,其他过渡金属基非传统超导材料相对较少,其中锰基超导材料尤其稀少.晶格维度的降低通常会抑制磁有序并增强自旋涨落,可以以此为思路探索新的锰基超导体.近年来,一个新的准一维锰基材料家族AMn_(6)Bi_(5)(A=Na,K,Rb和Cs)被发现.其中,AMn_(6)Bi_(5)(A=K,Rb和Cs)在高压下表现出非常规超导电性,加深了人们对于非常规超导与反铁磁关联的认识.

在不同润湿性条件下通过提高压差降低水驱残余油饱和度的系统研究

黏滞力和毛管力的比(一般表示为毛管数N_c)在确定残余油饱和度方面是至关重要的。在从接近中间润湿转变到强水湿的润湿性条件下,确定了通过系统增大N_c对均质白垩岩残余油饱和度的影响。在裂缝性白垩岩油藏中水驱残余油饱和度在很大程度上取决于润湿性。通过测量N_c不同时的可动油量,有助于确定三次采油的潜在目标。进行了一系列的注水驱油试验,以确定在不同润湿性条件下水驱中残余油量和增大毛管数之间的关系。通过Amott试验,用21个岩心柱样品建立并且量化了各种均匀分布混合润湿性条件。在水的Amott指数为0.3的润湿性条件下,N_c稳定时残余油最少。残余油饱和度随着毛管数增大而降低,在中等水湿到接近中间润湿条件下,水自吸后捕集的大量油开始流动。当增大毛管数时,在白垩岩油藏中得到的结果与在文献中报道的砂岩水驱残余油饱和度(随着润湿性和注入水PV变化)的结果相似。在采收率随着毛管教增加同时提高的情况下,采收率的穹隆形曲线(随着润湿性变化)反映了与较早水驱采收结果的相似性。

通过氮含量调控ZrN薄膜中的超导圆顶

超导圆顶作为非常规超导材料的一个常见特征,其存在经常被用来作为区分常规与非常规超导材料的判别标准.本文利用脉冲激光沉积氮化锆薄膜,并通过改变薄膜中的氮含量,实现了超导圆顶于绝缘态附近的调控。利用电学输运、磁性表征、太赫兹光谱、拉曼散射和透射电镜综合实验手段与密度泛函计算,作者发现氮化锆薄膜正常态存在从强绝缘到金属态再到弱绝缘的转变,其电阻率表现出类似于非常规超导的线性温度依赖到二次温度依赖特征.而氮化锆超导能隙及其转变温度符合BCS预期,其超导圆顶的演化与材料中电声耦合强度及结构无序相关,这项工作为“常规”超导材料中存在的“非常规”超导圆顶提供了强有力的证据与实例.