Among the various two-dimensional(2D)materials,more than 99%of them are noncentrosymmetric.However,since the commonly used substrates are generally centrosymmetric,antiparallel islands are usually inevitable in the gr...Among the various two-dimensional(2D)materials,more than 99%of them are noncentrosymmetric.However,since the commonly used substrates are generally centrosymmetric,antiparallel islands are usually inevitable in the growth of noncentrosymmetric 2D materials because of the energetic equivalency of these two kinds of antiparallel islands on centrosymmetric substrates.Therefore,achieving the growth of noncentrosymmetric 2D single crystals has long been a great challenge compared with the centrosymmetric ones like graphene.In this review,we presented the remarkable efforts and progress in the past decade,through precise chemical processes.We first discussed the great challenge and possible strategies in the growth of noncentrosymmetric 2D single crystals.Then,we focused on the advancements made in producing representative noncentrosymmetric 2D single crystals,including hexagonal boron nitride(hBN),transition metal dichalcogenides(TMDs),and other noncentrosymmetric 2D materials.At last,we summarized and looked forward to future research on the growth of layer-,stacking-,and twist-controlled noncentrosymmetric 2D single crystals and their heterostructures.展开更多
The noncentrosymmetric superconductor CaPtAs with time-reversal symmetry breaking in its superconducting state was previously proposed to host nodal superconductivity.Here,by employing ultralow-temperature thermal con...The noncentrosymmetric superconductor CaPtAs with time-reversal symmetry breaking in its superconducting state was previously proposed to host nodal superconductivity.Here,by employing ultralow-temperature thermal conductivity measurement on CaPtAs single crystal,we study its superconducting gap structure.A negligible residual linear term of thermal conductivity(κ_(0)/T)in zero magnetic field and the field dependence ofκ_(0)/T indicate that CaPtAs has multiple superconducting gaps with a dominant s-wave component.This is consistent with recent nuclear quadrupole resonance measurements on CaPtAs.Our work puts a strong constraint on the theories to describe the superconducting pairing symmetry of CaPtAs.展开更多
We report the discovery of a new noncentrosymmetric superconductor CaPtAs.It crystallizes in a tetragonal structure(space group I41md,No.109),featuring three dimensional honeycomb networks of Pt-As and a much elongate...We report the discovery of a new noncentrosymmetric superconductor CaPtAs.It crystallizes in a tetragonal structure(space group I41md,No.109),featuring three dimensional honeycomb networks of Pt-As and a much elongated c-axis(a=b=4.18?,and c=43.70?).The superconductivity of CaPtAs with Tc=1.47 K was characterized by means of electrical resistivity,specific heat,and ac magnetic susceptibility.The electronic specific heat Ce(T)/T shows evidence for a deviation from the behavior of a conventional BCS superconductor,and can be reasonably fitted by a p-wave model.The upper critical fieldμ0Hc2 of CaPtAs exhibits a moderate anisotropy,with an in-plane value of around 204 mT and an out-of-plane value of 148 mT.Density functional theory calculations indicate that the Pt-5 d and As-4 p orbitals mainly contribute to the density of states near the Fermi level,showing that the Pt-As honeycomb networks may significantly influence the superconducting properties.展开更多
We study the Josephson effect between two noncentrosymmetric superconductors（NCSs） with opposite polarization vectors of Rashba spin–orbit coupling（RSOC）.We find a 0–π transition driven by the triplet–singlet ...We study the Josephson effect between two noncentrosymmetric superconductors（NCSs） with opposite polarization vectors of Rashba spin–orbit coupling（RSOC）.We find a 0–π transition driven by the triplet–singlet ratio of NCSs.Different from conventional 0–π transitions,the Andreev bound states change their energy range instead of phase shift in the 0–π transition found here.This novel property results in a feature that the critical current becomes almost zero at the transition point,not only a minimum.Furthermore,when the directions of RSOC polarization vectors are the same in two NCSs,the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin–orbit coupling in the interlayer.We find novel oscillations of critical current without 0–π transition.These novel 0–π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet–singlet ratio of NCSs.展开更多
Four new deficient compounds in the R6B2C2QI4 family, LasCaSn2.75S4 1, Y6A10.67Ge2S14 2, Er5.33Si4S14 3 and Er4Ge4SI4 4, have been obtained via a precursor/flux method. Single-crystal analysis indicated that their cry...Four new deficient compounds in the R6B2C2QI4 family, LasCaSn2.75S4 1, Y6A10.67Ge2S14 2, Er5.33Si4S14 3 and Er4Ge4SI4 4, have been obtained via a precursor/flux method. Single-crystal analysis indicated that their crystal structures consist of three types of building blocks： RS7 （R = La/Ca for 1, R = Y for 2, R = Er for 3 and 4） mono-triangonal prism, CS6 （C = A1 for 1, C = Sn（2） for 2, C = Si（2） for 3, C = Ge（2） for 4） octahedron, and BS4 （B = Si for 1, B = Sn（1） for 2, B = Si（1） for 3, B = Ge（1） for 4） tetrahedron, as any other compounds belong to the R6B2C2Q14 family.展开更多
LaOsSi3 single crystals are synthesized for the first time by an arc melting method. The crystal features a tetrag- onal BaNiSn3-type structure （space group 14mm） which lacks inversion symmetry along the crystallogr...LaOsSi3 single crystals are synthesized for the first time by an arc melting method. The crystal features a tetrag- onal BaNiSn3-type structure （space group 14mm） which lacks inversion symmetry along the crystallographic c axis and is isostructural with the intensively studied Rashba-type noncentrosymmetric superconductors LaRhSi3 and LaIrSi3. Un- like LaRhSi3 and LaIrSi3 displaying superconductivity, LaOsSi3 shows only metallic behavior over the measured temper- ature range of 2 K-300 K. The Sommerfeld coefficient ]/derived from specific heat is 5.76 mJ.mol-1 -K-2, indicating that LaOsSi3 has a weak electronic correlation effect. The absence of superconductivity in LaOsSi3 may lie in the Os 5d bands in the electronic structure. If it is true, it would be useful to provide complementary knowledge in understanding the relation between conduction and the d bands of M in LaMSi3 compounds （M = transition metals）.展开更多
A new noncentrosymmetric phosphide ThIrP has been synthesized and characterized. X-ray difraction analysis shows that this compound crystallizes in a LaPtSi-type tetragonal lattice(space group I41md, Z = 4), whose lat...A new noncentrosymmetric phosphide ThIrP has been synthesized and characterized. X-ray difraction analysis shows that this compound crystallizes in a LaPtSi-type tetragonal lattice(space group I41md, Z = 4), whose lattice parameters are a = b =4.0676(1) ?, c = 14.3354(2) ?, and V = 237.191(8) ?3. Moreover, ThIrP is discovered to be an intermediately coupled,type-Ⅱ superconductor with possibly multiple gaps below Tc= 5.07 K. The upper critical magnetic field, Sommerfield coefficient, and Ginzburg-Laudau parameter are determined based on physical property measurements, which are Bc2= 0.83 T, γ =7.5 mJ mol-1 K-2, and κGL= 7.5, respectively. The electronic band structure calculations point out nearly equal contributions of Ir and Th atoms on the density of states around the Fermi surface. In addition, the spin-orbit coupling induced band splitting reaches as large as 270 meV along the Γ-Z line. Our results suggest that ThIrP provides a platform to study the interplay between inversion-symmetry breaking, strong spin-orbit coupling, and superconductivity.展开更多
Summary of main observation and conclusion This work presents the synthesis, crystal structure and properties of a novel noncentrosymmetric (NCS) coordination polymer (CP), namely,(Me2NH2)3[BaLi(2,6-PyDC)3(H2O)](1)(2,...Summary of main observation and conclusion This work presents the synthesis, crystal structure and properties of a novel noncentrosymmetric (NCS) coordination polymer (CP), namely,(Me2NH2)3[BaLi(2,6-PyDC)3(H2O)](1)(2,6-PyDC = pyridine-2,6-dicarboxylate acid), which represents the first example of BaLi-CPs with 2,6-PyDC ligand. Single-crystal X-ray structural analysis reveals that the compound features a two-dimensional (2D) layered structure. The simplified structure of each layer belongs to the hcb topology. The second harmonic generation (SHG) response of 1 is about 0.5 times that of KH2PO4 (KDP) marker. What is more, 1 emits bright blue light upon the excitation of 365 nm UV light with the quantum yield (QX Ф) of 1.63%. The successful con struction of this compound convinces the feasibility of constructing NCS CPs via the combi nation of [BaL3] unit and Li(l) ion.展开更多
新型无机二阶非线性光学晶体材料在光电子领域(如频率变换、光调制、通信和信息处理等领域)有着重要的应用,是材料研究的前沿方向之一。1998年以来,人们利用易于发生二阶姜-泰勒效应的离子———d0过渡金属离子(e.g.Mo6+,W6+,V5+,Nb5+)...新型无机二阶非线性光学晶体材料在光电子领域(如频率变换、光调制、通信和信息处理等领域)有着重要的应用,是材料研究的前沿方向之一。1998年以来,人们利用易于发生二阶姜-泰勒效应的离子———d0过渡金属离子(e.g.Mo6+,W6+,V5+,Nb5+)和含有非成键孤对电子(stereochemically active lone pair,SCALP,e.g.I5+,Te4+,Se4+,Sn2+)的阳离子,合成了大量具有非中心对称结构(NCS)的化合物,其中许多显示出很强的倍频效应(>400×α-SiO2),它们是一类有应用前景的非线性光学晶体材料。本文将这些材料分成三类进行综述,即:只含一类二阶姜-泰勒离子(d0或SCALP)的化合物;同时包含两类二阶姜-泰勒离子的化合物以及包含二阶姜-泰勒离子和其他非中心对称基团(共轭π-硼酸盐体系、PO4四面体和d10离子)的化合物。本文分别就新材料探索、单晶生长等综述了近10年来基于二阶姜-泰勒效应的非线性光学晶体材料的研究进展。展开更多
基金This work was supported by Guangdong Major Project of Basic and Applied Basic Research(2021B030103000)the National Natural Science Foundation of China(12322406,52102043,52025023,51991342,52021006 and 61905215)+5 种基金the Key R&D Program of Guangdong Province(2020B010189001,2019B010931001,2018B010109009 and 2018B030327001)the Pearl River Talent Recruitment Program of Guangdong Province(2019ZT08C321)the Key Project of Science and Technology of Guangzhou(202201010383)the Natural Science Foundation o f Guangdong Provinces(2023A1515012743)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB3300000)the New Cornerstone Science Foundation through the XPLORER PRIZE.
文摘Among the various two-dimensional(2D)materials,more than 99%of them are noncentrosymmetric.However,since the commonly used substrates are generally centrosymmetric,antiparallel islands are usually inevitable in the growth of noncentrosymmetric 2D materials because of the energetic equivalency of these two kinds of antiparallel islands on centrosymmetric substrates.Therefore,achieving the growth of noncentrosymmetric 2D single crystals has long been a great challenge compared with the centrosymmetric ones like graphene.In this review,we presented the remarkable efforts and progress in the past decade,through precise chemical processes.We first discussed the great challenge and possible strategies in the growth of noncentrosymmetric 2D single crystals.Then,we focused on the advancements made in producing representative noncentrosymmetric 2D single crystals,including hexagonal boron nitride(hBN),transition metal dichalcogenides(TMDs),and other noncentrosymmetric 2D materials.At last,we summarized and looked forward to future research on the growth of layer-,stacking-,and twist-controlled noncentrosymmetric 2D single crystals and their heterostructures.
基金financial support by the foundation of Westlake University and the Service Center for Physical Sciences for technical assistance in SEM measurementssupported by the National Natural Science Foundation of China(12050003)。
基金Project supported by the National Natural Science Foundation of China (Grant No.12174064)the National Key R&D Program of China (Grant No.2022YFA1402200)the Shanghai Municipal Science and Technology Major Project (Grant No.2019SHZDZX01)。
文摘The noncentrosymmetric superconductor CaPtAs with time-reversal symmetry breaking in its superconducting state was previously proposed to host nodal superconductivity.Here,by employing ultralow-temperature thermal conductivity measurement on CaPtAs single crystal,we study its superconducting gap structure.A negligible residual linear term of thermal conductivity(κ_(0)/T)in zero magnetic field and the field dependence ofκ_(0)/T indicate that CaPtAs has multiple superconducting gaps with a dominant s-wave component.This is consistent with recent nuclear quadrupole resonance measurements on CaPtAs.Our work puts a strong constraint on the theories to describe the superconducting pairing symmetry of CaPtAs.
基金the National Key R&D Program of China(Grant Nos.2016YFA0300202,and 2017YFA0303100)the National Natural Science Foundation of China(Grant Nos.U1632275,and 11874320)+1 种基金the Science Challenge Project of China(Grant No.TZ2016004)the Fundamental Research Funds for the Central Universities.
文摘We report the discovery of a new noncentrosymmetric superconductor CaPtAs.It crystallizes in a tetragonal structure(space group I41md,No.109),featuring three dimensional honeycomb networks of Pt-As and a much elongated c-axis(a=b=4.18?,and c=43.70?).The superconductivity of CaPtAs with Tc=1.47 K was characterized by means of electrical resistivity,specific heat,and ac magnetic susceptibility.The electronic specific heat Ce(T)/T shows evidence for a deviation from the behavior of a conventional BCS superconductor,and can be reasonably fitted by a p-wave model.The upper critical fieldμ0Hc2 of CaPtAs exhibits a moderate anisotropy,with an in-plane value of around 204 mT and an out-of-plane value of 148 mT.Density functional theory calculations indicate that the Pt-5 d and As-4 p orbitals mainly contribute to the density of states near the Fermi level,showing that the Pt-As honeycomb networks may significantly influence the superconducting properties.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11204187 and 11274059)
文摘We study the Josephson effect between two noncentrosymmetric superconductors（NCSs） with opposite polarization vectors of Rashba spin–orbit coupling（RSOC）.We find a 0–π transition driven by the triplet–singlet ratio of NCSs.Different from conventional 0–π transitions,the Andreev bound states change their energy range instead of phase shift in the 0–π transition found here.This novel property results in a feature that the critical current becomes almost zero at the transition point,not only a minimum.Furthermore,when the directions of RSOC polarization vectors are the same in two NCSs,the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin–orbit coupling in the interlayer.We find novel oscillations of critical current without 0–π transition.These novel 0–π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet–singlet ratio of NCSs.
基金Supported by NNSFC(90922035,21003126)the Key Project from CAS(KJCX2-YW-H01,KJCX2-EW-H03)NSF of Fujian Province(A0420002)
文摘Four new deficient compounds in the R6B2C2QI4 family, LasCaSn2.75S4 1, Y6A10.67Ge2S14 2, Er5.33Si4S14 3 and Er4Ge4SI4 4, have been obtained via a precursor/flux method. Single-crystal analysis indicated that their crystal structures consist of three types of building blocks： RS7 （R = La/Ca for 1, R = Y for 2, R = Er for 3 and 4） mono-triangonal prism, CS6 （C = A1 for 1, C = Sn（2） for 2, C = Si（2） for 3, C = Ge（2） for 4） octahedron, and BS4 （B = Si for 1, B = Sn（1） for 2, B = Si（1） for 3, B = Ge（1） for 4） tetrahedron, as any other compounds belong to the R6B2C2Q14 family.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11274367,10904097,and 11274233) and Chinese Academy of Sciences
文摘LaOsSi3 single crystals are synthesized for the first time by an arc melting method. The crystal features a tetrag- onal BaNiSn3-type structure （space group 14mm） which lacks inversion symmetry along the crystallographic c axis and is isostructural with the intensively studied Rashba-type noncentrosymmetric superconductors LaRhSi3 and LaIrSi3. Un- like LaRhSi3 and LaIrSi3 displaying superconductivity, LaOsSi3 shows only metallic behavior over the measured temper- ature range of 2 K-300 K. The Sommerfeld coefficient ]/derived from specific heat is 5.76 mJ.mol-1 -K-2, indicating that LaOsSi3 has a weak electronic correlation effect. The absence of superconductivity in LaOsSi3 may lie in the Os 5d bands in the electronic structure. If it is true, it would be useful to provide complementary knowledge in understanding the relation between conduction and the d bands of M in LaMSi3 compounds （M = transition metals）.
基金financial support by the foundation of Westlake Universitysupported by the National Key Research Development Program of China (Grant No. 2017YFA0303002)the Fundamental Research Funds for the Central Universities of China。
文摘A new noncentrosymmetric phosphide ThIrP has been synthesized and characterized. X-ray difraction analysis shows that this compound crystallizes in a LaPtSi-type tetragonal lattice(space group I41md, Z = 4), whose lattice parameters are a = b =4.0676(1) ?, c = 14.3354(2) ?, and V = 237.191(8) ?3. Moreover, ThIrP is discovered to be an intermediately coupled,type-Ⅱ superconductor with possibly multiple gaps below Tc= 5.07 K. The upper critical magnetic field, Sommerfield coefficient, and Ginzburg-Laudau parameter are determined based on physical property measurements, which are Bc2= 0.83 T, γ =7.5 mJ mol-1 K-2, and κGL= 7.5, respectively. The electronic band structure calculations point out nearly equal contributions of Ir and Th atoms on the density of states around the Fermi surface. In addition, the spin-orbit coupling induced band splitting reaches as large as 270 meV along the Γ-Z line. Our results suggest that ThIrP provides a platform to study the interplay between inversion-symmetry breaking, strong spin-orbit coupling, and superconductivity.
基金the National Natural Science Foundation of China (No. 21601181)NSF of Fujian Province (No. 2016J05054).
文摘Summary of main observation and conclusion This work presents the synthesis, crystal structure and properties of a novel noncentrosymmetric (NCS) coordination polymer (CP), namely,(Me2NH2)3[BaLi(2,6-PyDC)3(H2O)](1)(2,6-PyDC = pyridine-2,6-dicarboxylate acid), which represents the first example of BaLi-CPs with 2,6-PyDC ligand. Single-crystal X-ray structural analysis reveals that the compound features a two-dimensional (2D) layered structure. The simplified structure of each layer belongs to the hcb topology. The second harmonic generation (SHG) response of 1 is about 0.5 times that of KH2PO4 (KDP) marker. What is more, 1 emits bright blue light upon the excitation of 365 nm UV light with the quantum yield (QX Ф) of 1.63%. The successful con struction of this compound convinces the feasibility of constructing NCS CPs via the combi nation of [BaL3] unit and Li(l) ion.
基金supported by the Key R&D Program of Zhejiang Province,China(2021C01002)the National Natural Science Foundation of China(11874320,12034017,11874137,and 11974306)+1 种基金the National Key R&D Program of China(2017YFA0303100)Zhejiang Provincial Natural Science Foundation of China(R22A0410240).
文摘新型无机二阶非线性光学晶体材料在光电子领域(如频率变换、光调制、通信和信息处理等领域)有着重要的应用,是材料研究的前沿方向之一。1998年以来,人们利用易于发生二阶姜-泰勒效应的离子———d0过渡金属离子(e.g.Mo6+,W6+,V5+,Nb5+)和含有非成键孤对电子(stereochemically active lone pair,SCALP,e.g.I5+,Te4+,Se4+,Sn2+)的阳离子,合成了大量具有非中心对称结构(NCS)的化合物,其中许多显示出很强的倍频效应(>400×α-SiO2),它们是一类有应用前景的非线性光学晶体材料。本文将这些材料分成三类进行综述,即:只含一类二阶姜-泰勒离子(d0或SCALP)的化合物;同时包含两类二阶姜-泰勒离子的化合物以及包含二阶姜-泰勒离子和其他非中心对称基团(共轭π-硼酸盐体系、PO4四面体和d10离子)的化合物。本文分别就新材料探索、单晶生长等综述了近10年来基于二阶姜-泰勒效应的非线性光学晶体材料的研究进展。
