Related papers: Linear decrease of critical temperature with incre…
We show that, in contrast with the usual electron-phonon Migdal-Eliashberg theory, the critical temperature Tc of an isotropic s-wave nonadiabatic superconductor is strongly reduced by the presence of diluted non-magnetic impurities. Our…
Using Tyablikov's decoupling approximation, we calculate the initial suppression rate of the Neel temperature, $R_{IS}=-lim_{x-> 0} T^{-1}_{N} dT_{N}/dx$, in a quasi two-dimensional diluted Heisenberg antiferromagnet with nonmagnetic…
We report on the effect of substitution for Cu on Tc of electron-doped infinite-layer superconductors Sr0.9La0.1Cu1-xRxO2, R = Zn and Ni. We found that Tc was nearly constant until x = 0.03 for R = Zn, while superconductivity was nearly…
Based on the five-orbital model, we derive the reduced impurity scattering rate $g=z\gamma/2\pi T_{c0}$ in Sm(Fe$_{1-x}$Ru$_{x}$)AsO$_{0.85}$F$_{0.15}$ from the residual resistivity. At $x=0$, the transition temperature is $T_{c0}=50$ K.…
The transport behavior and superconducting transition temperature Tc of NdFe1-yRuyAsO0.89F0.11 have been studied for various y values. Because Ru impurities are isoelectronic to host Fe atoms, we basically expect that the number of…
It has been observed that impurity doping and/or ion-beam-induced damage in high $T_{c}$ superconductors cause a metal-insulator transition and thereby suppress the critical temperature. Based on our recent theory of the weak localization…
We report an NMR investigation of the superconductivity in BaFe(2)As(2) induced by Co doping (Tc=22K). We demonstrate that Co atoms form an alloy with Fe atoms and donate carriers without creating localized moments. Our finding strongly…
The thermal conductivity of Zn-doped YBCO crystals was studied at low temperature (0.15 < T < 0.8 K) for different concentrations of Zn impurities. A small amount of Zn induces a dramatic decrease in the non-linear component of the…
Effects of magnetic impurity on the superconductivity has been investigated in Mg1-xMnB2. With increase of Mn concentration x, the lattice constant c (perpendicular to the boron sheet) decreases at a rate of -1.4 % (= dlnc/dx), while a…
Non-magnetic impurities in iron-based superconductors can provide an important tool to understand the pair symmetry and they can influence significantly the transport and the superconducting behaviour. Here, we present a study of the role…
We report the effect on the superconducting transition temperature (Tc) of a Nb film proximity coupled to the synthetic antiferromagnet Fe/{Cr/Fe}_(N-1). We find that there is a parity dependence of Tc on the total number of Fe layers, N;…
Copper and Nickel impurities have been doped into the iron pnictide superconductor Ba0.6K0.4Fe2As2. Resistivity measurements reveal that Cu and Ni impurities suppress superconducting transition temperature T_c with rates of \Delta T_c/Cu-1%…
Application of pressures or electron-doping through Co substitution into Fe sites transforms the itinerant antiferromagnet BaFe(2)As(2) into a superconductor with the Tc exceeding 20K. We carried out systematic transport measurements of…
We described the effect of nonmagnetic impurity on the superconductivity behavior of the NdFeAsO0.8F0.2 iron-based superconductor. The resistivity measurement showed that the superconductivity suppressed upon increasing the low amounts of…
$^{75}$As and $^{139}$La NMR and nuclear quadrupole resonance (NQR) studies on Zn-substituted LaFeAsO$_{0.85}$ have been performed to investigate the Zn-impurity effects microscopically. Although superconductivity in LaFeAsO$_{0.85}$…
We investigated the electrical conductivity, thermal conductivity and thermopower as a function of Nb content (x) in Ba0.7Eu0.3Ti1-xNbxO3 (x = 0.001- 0.10) in the temperature range T = 400-2 K. The substitution of Nb destabilizes the…
We report the specific heat discontinuity, deltaC/Tc, at Tc = 28.2 K of a collage of single crystals of BaFe2(As0.7P0.3)2 and compare the measured value of 38.5 mJ/molK**2 with other iron pnictide and iron chalcogenide (FePn/Ch)…
Irradiation with 2.5 MeV electrons at doses up to 5.2 $\times$10$^{19}$ electrons/cm$^2$ was used to introduce point-like defects in single crystals of Ba$_{1-x}$K$_x$Fe$_2$As$_2$ with $x=$ 0.19 ($T_c=$ 14 K), $x=$ 0.26 ($T_c=$ 32 K) and…
We present a systematic study of the impurity effect on Tc in Fe-based superconductors, assuming that the sign-reversal s-wave state due to inter-pocket repulsion ($s_\pm$-wave state) is realized. For this purpose, we introduce several…
We report the effect of 3 MeV proton irradiation on the suppression of the critical temperature $T_{c}$ in Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ single crystals at under-, optimal-, and over-doping levels. We find that $T_{c}$ decreases and…