Electron-hole asymmetry in the doping dependence
of spectral function for high-Tc cuprates

Takami Tohyama

Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan

We examine the doping dependence of the spectral function in the hole- and electron-doped cuprates by using the t-t'-t''-J model. The spectral function at zero temperature is numerically calculated for a full range of the Brillouin zone by introducing the twisted boundary conditions for small clusters. Remarkable differences are found between hole- and electron-dopings. Along the nodal direction quasiparticle bands in the hole-doped system are gapless as expected, while in electron doping the bands are gapped up to optimum doping. The gap is found to be correlated with the strength of antiferromagnetic correlation, indicating that the gap is magnetically driven. Thus, the d-wave superconductivity in the electron-doped system is intimately related to the closing of the gap. The spectral functions around the antinodal region show contrasting behaviors: a gap-like feature appears in hole doping but not in electron doping, leading to a Fermi-arc behavior only in hole-doped system. These results would give a new insight on the doping dependence of the electronic states in high-Tc cuprates.