Resonant States of a Momentum-Dependent Impurity Potential in a d-Wave Superconductor

Abstract

Controlled impurity substitution is an important tool in the identification of a symmetry of the superconducting ground state. Particularly efficient are the scanning tunneling microscopy (STM) measurements of the local density of states (LDOS) which probe directly and with atomic precision excited states in the vicinity of the impurity atom. STM measurements of LDOS around single Zn [1] or Ni [2] impurity atom as well as Cu vacancy [3] in superconducting Bi2Sr2CaCu2O8+δ revealed a distinct fourfold symmetry of LDOS specific for a d-wave superconductor. Although, the main features of complex STM patterns in cuprates are captured by a model on-site impurity scattering [4–6], studies of extended impurity potentials [7–9] are motivated by some still unresolved features of LDOS in these compounds [10]. We continue the issue of anisotropic in the reciprocal space impurity potential [11–15] and discuss its effect on the impurity-bound states in high-temperature superconductors.