Rapid Suppression Of Superconductivity Research Articles

Control of the superconducting properties of Sr2−xCaxVO3FeAs through isovalent substitution

The effect of the isovalent substitution of Sr2+ by Ca2+ on the structure and superconducting properties of Sr2−xCaxVO3FeAs is described in the compositional range 0≤x≤0.5. SQUID magnetometry measurements reveal that after an initial increase in Tc, which is maximised at 29.5K in Sr1.95Ca0.05VO3FeAs, a rapid suppression of superconductivity is observed with increasing x. XANES spectra of Sr2−xCaxVO3FeAs collected on the Fe and V absorption K-edges show that the position of both edges are invariant with composition within the experimental uncertainty. A combination of synchrotron X-ray powder diffraction and neutron powder diffraction techniques is used to rationalise the observed changes in Tc with x, in terms of changes to the structure of the FeAs layer upon partial Ca substitution. These findings demonstrate that superconductivity in the Fe-based superconductors is extremely sensitive to the crystal structure with Tc maximised in samples with regular FeAs4-tetrahedra.

Role of 3d electrons in the rapid suppression of superconductivity in the dilute V doped spinel superconductorLiTi2O4

The microscopic effects of V doping inLiTi2O4 have been poorly understood. The present study employs x-ray absorption near-edgestructure (XANES) and resonant inelastic soft-x-ray scattering (RIXS) spectroscopy tounderstand the change in the electronic structure due to dilute V doping in spinelLiTi2O4 and the possible origin for the rapid suppression of superconductivity in these compounds.Results from the XANES spectra at Ti L and K edges and Ti L-RIXS show that Ti exists ina mixed-valence state and, with V doping, the unoccupied states of Ti in thet2g band increase. The rapid suppression of superconductivity is associated with the change inTi 3d electrons and Ti–O hybridization.

Suppression of superconductivity in Mn-substitutedMgCNi3

We report the effect of doping Mn in the isostructural ${\mathrm{MgCNi}}_{3\ensuremath{-}x}{\mathrm{Mn}}_{x}$ $(x=0--0.05)$ compounds. Magnetic susceptibility, resistivity, magnetoresistance, and specific heat studies show evidence of localized moments and Kondo effect in samples with $x\ensuremath{\ne}0.$ The rapid suppression of superconductivity $(\ensuremath{\sim}\ensuremath{-}21\mathrm{K}/\mathrm{a}\mathrm{t}.%$ Mn) in these compounds is a consequence of pair breaking effects due to moment formation on Mn.

Superconducting and normal state properties of Y 1− xPr xNi 2B 2C

Electrical resistivity, magnetoresistance and magnetic susceptibility have been studied for Y 1− x Pr x Ni 2B 2C samples with 0⩽ x⩽1.0. The increase of Pr concentration x results in a rapid suppression of superconductivity, |d T c/d x|=35 K. No indication on superconductivity was observed for PrNi 2B 2C down to T=0.35 K. The absence of superconductivity for PrNi 2B 2C and the large superconductivity suppression rate |d T c/d x| for Y 1− x Pr x Ni 2B 2C correlate with the anomalously high Néel temperature of PrNi 2B 2C ( T N≈4 K). Possible reasons for the absence of superconductivity in PrNi 2B 2C and the large |d T c/d x| value for Y 1− x Pr x Ni 2B 2C are discussed.

Nonmagnetic impurities in two-dimensional superconductors.

A numerical approach to disordered two-dimensional superconductors described by BCS mean-field theory is outlined. The energy gap and the superfluid density at zero temperature and the quasiparticle density of states are studied. The method involves approximate self-consistent solutions of the Bogolubov--de Gennes equations on finite square lattices. Where comparison is possible, the results of standard analytic approaches to this problem are reproduced. Detailed modeling of impurity effects is practical using this approach. The range of the impurity potential is shown to be of quantitative importance in the case of strong potential scatterers. We discuss the implications for experiments, such as the rapid suppression of superconductivity by Zn doping in copper-oxide superconductors.

EFFECT OF DOPING Zn ON THE ELECTRONIC STRUCTURE Of La1.85Sr0.15CuO4

The change of the electronic structure of La 1.85 Sr 0.15 CuO 4 caused by the local substitution of Zn for Cu has been calculated by the recursion method. The partial wave density of states, the intensity of bonds, and the atomic valence, etc. are obviously affected by Zn on the doped site and its neighbors. The 2D electronic structure and magnetic structure are destroyed locally. We think these, together with the local increase of Cu holes, decrease of O2 holes, and the inducement of a net magnetic moment of 1.3 µB are responsible for the rapid suppression of superconductivity in Zn-doped La 1.85 Sr 0.15 CuO 4 materials.