Anomalous isotope effect in high-temperature superconductor LSCO with 3d-impurities

2003

Phys. Rev. B

The isotope effect in impure high T c superconductors. The influence of various kinds of impurities on the isotope shift exponent α of high temperature superconductors has been studied. In these materials the dopant impurities, like Sr in La2−xSrxCuO4, play different role and usually occupy different sites than impurities like Zn, Fe, Ni etc intentionally introduced into the system to study its superconducting properties. In the paper the in-plane and out-of-plane impurities present in layered superconductors have been considered. They differently affect the superconducting transition temperature Tc. The relative change of isotope shift coefficient, however, is an universal function of Tc/Tc0 (Tc0 reffers to impurity free system) i.e. for angle independent scattering rate and density of states function it does not depend whether the change of Tc is due to in-or out-of-plane impurities. The role of the anisotropic impurity scattering in changing oxygen isotope coefficient of superconductors with various symmetries of the order parameter is elucidated. The comparison of the calculated and experimental dependence of α/α0, where α0 is the clean system isotope shift coefficient, on Tc/Tc0 is presented for a number of cases studied. The changes of α calculated within stripe model of superconductivity in copper oxides resonably well describe the data on La1.8Sr0.2Cu1−x(F e, N i)xO4, without any fitting parameters.

Section: Discussionsupporting

confidence: 92%

Section: A Impurities In D-wave Superconductormentioning

confidence: 99%

Section: B Impurity Effects In S-wave Layered Superconductormentioning

confidence: 99%

“…(26,27). The data points are experimental values for overdoped La1.80Sr0.20Cu1−xMxO4, with Ni (filled triangles), Fe (circles) [18].…”

Section: Isotope Effect In Impure Striped Cupratesmentioning

confidence: 99%

See 2 more Smart Citations

Isotope effect in impure high-Tcsuperconductors

2003

Phys. Rev. B

“…In high temperature superconductors (HTS) [1] the isotope effect [2][3][4] shows complex behaviour: it takes on very small values for optimally doped samples and increases with decreasing oxygent content δ in YBa 2 Cu 3 O 7−δ and decreasing transition temperature. Similar behaviour is observed in samples doped with such metals as Fe, Co, Zn, etc.…”

Section: Introductionmentioning

confidence: 99%

The Isotope Effect of Disordered Superconductors

2004

Acta Phys. Pol. A

The isotope effects in disordered weak and strong coupling superconductors of different symmetries of the order parameter have been studied. We have found that even though weak localisation corrections to Eliashberg equations describe a strong degradation of transition temperature with disorder of s-wave superconductors, their influence on isotope coefficient is relatively weak. On the other hand the calculated change of relative isotope coefficient with T c /T c0 in homogeneous thin film materials is similar to that observed in high temperature superconductors.

The isotope effect in disordered strongly coupled superconductors

Physica Status Solidi (b)

2006

The isotope effect in disordered strongly coupled superconductors has been studied. Weakly disordered bulk s-and d-wave superconductors as well as strongly disordered homogeneous and granular thin films have been considered. To treat strong coupling s-wave superconductors Eliashberg theory has been used and the weak localization effects on isotope coefficient (IC) calculated within this approach. The interesting point is that weak localization effects known to properly describe degradation of transition temperature of s-wave superconductors have been found to decrease the isotope coefficient of impure material with respect to pure samples. This is in contrast to the strong increase of IC induced by magnetic impurities in s-wave or nonmagnetic impurities in d-wave spin singlet superconductors. We have also calculated the change of isotope coefficient for both homogeneous and granular thin films and found that the effect of disorder in granular materials on the isotope coefficient is similar to that observed in high-temperature superconductors.