Ultralow-temperature heat transport study of noncentrosymmetric superconductor CaPtAs

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.

Crystal growth,structural and physical properties of the 5d noncentrosymmetric LaOsSi_3

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）.

Novel 0–π transitions in Josephson junctions between noncentrosymmetric superconductors

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.

Superconductivity and strong spin-orbit coupling in a new noncentrosymmetric compound ThIrP

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.

Construction of a Noncentrosymmetric Luminescent Coordination Polymer from [BaL3] Unit (L = Pyridine-2,6-dicarboxylate Acid) and Li(l) Ion

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.

CaPtAs: A new noncentrosymmetric superconductor

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.

Syntheses and Single-crystal Structures of New Deficient Compounds in the R_6B_2C_2Q_(14)Family

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.