Effect of Zn and Ni Impurities on the Quasiparticle Renormalization of Superconducting Bi-2212

The Cu substitution by Zn and Ni impurities and its influence on the mass renormalization effects in angle-resolved photoelectron spectra (ARPES) of ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8-\delta }$ is addressed. We show that the nonmagnetic Zn atoms have a much stronger effect in both the nodal and antinodal parts of the Brillouin zone than magnetic Ni. The observed changes are consistent with the behavior of the spin resonance mode as seen by inelastic neutron scattering in YBCO. This strongly suggests that the “peak-dip-hump” and the kink in ARPES on the one side and neutron resonance on the other are closely related features.

Figure 1

(a) Cut of a $k\omega$ space at the Fermi level. The top of the cube contains two sheets of the Fermi surface; the red solid line corresponds to the dispersion of the antibonding band; the blue dashed one to the bonding band. (b) Model line shape of the $(\pi ,0)$ EDC, when coupled to a narrow (2 meV) and broad (20 meV) collective mode. (c) Experimental EDC’s taken at the $(\pi ,0)$ point.

Figure 2

(a)–(c) Photoemission intensity distributions along the BZ diagonal. (a) Pure BSCCO, (b) Ni substituted, and (c) Zn substituted BSCCO. The middle row shows corresponding experimental dispersion. In the last row, the real part of the self-energy obtained by subtractions of the bare band is displayed. The black solid lines are guides to eye, while the red symbols represent the data points.

Figure 3

Cuts of $k\omega$ space made 20 meV below the Fermi level and tight-binding fits. (a) Ni substituted sample. (b) Zn substituted sample. (c) Pure BSCCO close to optimal doping. (d) Overdoped BSCCO, $\delta \approx 0.20$; L denotes lens formed by the shadow band and the 1st order diffraction replica.