arXiv:cond-mat/0702457 · Physical Review B
Impurity resonant state in d -wave superconductors: In favor of a Kondo-like response
Marijana Kirćan
Abstract
We investigate the impurity resonant state induced by nonmagnetic impurities in $d$-wave cuprate superconductors in two different impurity models: (i) in a pure potential scattering model within the $T$-matrix approach and (ii) in a Bose--Fermi Kondo model within the large-$\mathcal{N}$ formalism. We modify the superconducting host to resemble the nanoscale electronic inhomogeneities seen in the scanning tunneling microscopy (STM) spectra (i.e., the small-and large-gap domains) and study how this influences the impurity resonance. In the pure potential scattering model, the resonant state is found to be a rather robust feature appearing in all host domains. On the other hand, in the Kondo-like model the impurity resonance can appear in the small-gap regions of the host and be completely suppressed in the large-gap regions; this is in agreement with the STM experimental data for Zn-doped ${\text{Bi}}_{2}{\text{Sr}}_{2}{\text{CaCu}}_{2}{\text{O}}_{8+\ensuremath{\delta}}$. Our results imply that the Kondo spin dynamics of the impurity moment is the origin of the impurity resonant state in $d$-wave superconductors, rather than the pure potential scattering.