Using an optimization variational Monte Carlo method, we study the effect of diagonal transfer t′ in a two-dimensional Hubbard model on stability of d-wave superconductivity (SC) and antiferromagnetism (AF). For hole doping (t′/t<0), the condensation energy of SC is enhanced by a couple of times, while that of AF rapidly decreases with increasing |t′/t|, and AF itself is intrinsically unstable for t′/t≲0. For electron doping (t′/t>0), conversely, SC tends to be suppressed, whereas the AF state not only comes to have a low energy but recovers the intrinsic stability. These results well explain various aspects of cuprate superconductors.
- D. Superconductivity