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Register a new userPhysical properties of noncentrosymmetric superconductor LaIrSi3: A {mu}SR study
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The results of heat capacity C_p(T, H) and electrical resistivity rho(T,H) measurements down to 0.35 K as well as muon spin relaxation and rotation (muSR) measurements on a noncentrosymmetric superconductor LaIrSi3 are presented. Powder neutron diffraction confirmed the reported noncentrosymmetric body-centered tetragonal BaNiSn3-type structure (space group I4,mm) of LaIrSi3. The bulk superconductivity is observed below T_c = 0.72(1) K. The intrinsic Delta C_e/gamma_n T_c = 1.09(3) is significantly smaller than the BCS value of 1.43, and this reduction is accounted by the alpha-model of BCS superconductivity. The analysis of the superconducting state C_e(T) data by the single-band alpha-model indicates a moderately anisotropic order parameter with the s-wave gap Delta(0)/k_B T_c = 1.54(2) which is lower than the BCS value of 1.764. Our estimates of various normal and superconducting state parameters indicate a weakly coupled electron-phonon driven type-I s-wave superconductivity in LaIrSi3. The muSR results also confirm the conventional type-I superconductivity in LaIrSi3 with a preserved time reversal symmetry and hence a singlet pairing superconducting ground state.
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Transition metal boride Ru$_7$B$_3$ was found to be a noncentrosymmetric superconductor with $T_{C}$ equal to 3.3 K. Superconducting and normal state properties of Ru$_7$B$_3$ were determined by a self-consistent analysis through resistivity($rho_{xx}$ and $rho_{xy}$), specific heat, lower critical field measurement and electronic band structure calculation. It is found that Ru$_7$B$_3$ belongs to an s-wave dominated single band superconductor with energy gap 0.5 meV and could be categorized into type II superconductor with weak electron-phonon coupling. Unusual kink feature is clearly observed in field-broadening resistivity curves, suggesting the possible mixture of spin triplet induced by the lattice without inversion symmetry.
The newly found superconductivity in infinite-layer nickelate superconducting films has attracted much attention, because their crystalline and electronic structures are similar to high-$T_c$ cuprate superconductors. The upper critical field can provide much information on superconductivity, but detailed experimental data are still lacking in these films. Here we present temperature and angle dependence of resistivity measured under different magnetic fields ($H$) in Nd$_{0.8}$Sr$_{0.2}$NiO$_{2}$ thin films. The onset superconducting transition occurs at about 16.2 K at 0 T. Temperature dependent upper critical fields determined by using a criterion very close to the onset transition show a clear negative curvature near the critical transition temperature, which is explained as the consequence of the paramagnetically limited effect on superconductivity. The temperature dependent anisotropy of the upper critical field is obtained from resistivity data, which yields a value decreasing from 3 to 1.2 with lowering temperature. This can be explained by a variable contribution from the orbital limit effect on upper critical field. The angle dependent resistivity at a fixed temperature and different magnetic fields cannot be scaled to one curve, which deviates from the prediction of the anisotropic Ginzburg-Landau theory. However, at low temperatures, the increased resistivity by magnetic field can be scaled by the parameter $H^beta |costheta|$ ($1<beta<6$) with $theta$ the angle enclosed between $c$-axis and the applied magnetic field. As the first detailed study on the upper critical field of the nickelate thin films, our results clearly indicate a small anisotropy and paramagnetically limited effect of superconductivity in nickelate superconductors.
We report a comprehensive study of the noncentrosymmetric superconductor Mo$_3$P. Its bulk superconductivity, with $T_c = 5.5$ K, was characterized via electrical resistivity, magnetization, and heat-capacity measurements, while its microscopic electronic properties were investigated by means of muon-spin rotation/relaxation ($mu$SR) and nuclear magnetic resonance (NMR) techniques. In the normal state, NMR relaxation data indicate an almost ideal metallic behavior, confirmed by band-structure calculations, which suggest a relatively high electron density of states, dominated by the Mo $4d$-orbitals. The low-temperature superfluid density, determined via transverse-field $mu$SR and electronic specific heat, suggest a fully-gapped superconducting state in Mo$_3$P, with $Delta_0= 0.83$ meV, the same as the BCS gap value in the weak-coupling case, and a zero-temperature magnetic penetration depth $lambda_0 = 126$ nm. The absence of spontaneous magnetic fields below the onset of superconductivity, as determined from zero-field $mu$SR measurements, indicates a preserved time-reversal symmetry in the superconducting state of Mo$_3$P and, hence, spin-singlet pairing.
A large variety of perovskite oxide superconductors are known, including some of the most prominent high-temperature and unconventional superconductors. However, superconductivity among the oxidation state inverted material class, the antiperovskite oxides, was reported just recently for the first time. In this superconductor, Sr$_{3-x}$SnO, the unconventional ionic state Sn$^{4-}$ is realized and possible unconventional superconductivity due to a band inversion has been discussed. Here, we discuss an improved facile synthesis method, making it possible to control the strontium deficiency in Sr$_{3-x}$SnO. Additionally, a synthesis method above the melting point of Sr$_{3}$SnO is presented. We show temperature dependence of magnetization and electrical resistivity for superconducting strontium deficient Sr$_{3-x}$SnO ($T_{mathrm{c}}$ ~ 5 K) and for Sr$_{3}$SnO without a superconducting transition down to 0.15 K. Further, we reveal a significant effect of strontium raw material purity on the superconductivity and achieve 40% increased superconducting volume fraction (~100%) compared to the highest value reported so far. More detailed characterisation utilising powder X-ray diffraction and energy-dispersive X-ray spectroscopy show that a minor cubic phase, previously suggested to be a Sr$_{3-x}$SnO, is SrO. The improved characterization and controlled synthesis reported herein enable detailed investigations on the superconducting nature and its dependency on the strontium deficiency in Sr$_{3-x}$SnO.
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