Quasiparticle states around a nonmagnetic impurity in a d-density-wave state of high-T_c cuprates

The electronic structure around a single nonmagnetic impurity in the d-density-wave (DDW) ordering is studied. It is found that a single subgap resonance peak appears in the local density of states around the impurity. In the unitary limit, the position of this resonance peak shifts away from the Fermi energy in accord with the chemical potential. This result is dramatically different from the case of the pure superconducting state for which the impurity resonant energy is approximately pinned at the Fermi level. This can be used to probe the existence of the DDW ordering in cuprates.