Impurity effects on electron–mode coupling in high-temperature superconductors

Impurity states and interlayer tunneling in high temperature superconductors.

We argue that the scanning tunneling microscope (STM) images of resonant states generated by doping Zn or Ni impurities into Cu-O planes of BSCCO are the result of quantum interference of the impurity signal coming from several distinct paths. The impurity image seen on the surface is greatly affected by interlayer tunneling matrix elements. We find that the optimal tunneling path between the S...

Anomalous impurity effects in nonadiabatic superconductors

– 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 results suggest that the recently observed Tc-suppression driven by disorder in K3C60 (Phys. Rev. B 55, 3866 (1997)) and in Nd2−xCexCuO4−δ (Phys. Rev. B 58, ...

Impurity-Induced Bound States in Superconductors with Spin-Orbit Coupling.

We study the effect of strong spin-orbit coupling (SOC) on bound states induced by impurities in superconductors. The presence of SOC breaks the SU(2)-spin symmetry and causes the superconducting order parameter to have generically both singlet (s-wave) and triplet (p-wave) components. We find that in the presence of SOC the spectrum of Yu-Shiba-Rusinov (YSR) states is qualitatively different i...

Are the New High Temperature Superconductors Strong Coupling Systems?*

Under certain circumstances the excitations of a superconductor will not be those predicted by BCS theory, but rather electron bag states. A variational calculation is used to establish this regime in which such collective states form. The fact that such bags may bind more than one electron implies the existence of more than one peak in the plots of dl/dV versus Vp obtained in Giaver tunneling ...

Impurity Eeects in Superconductors