Stripes and superconductivity in high-Tc superconductors

The ground state of the three-band Hubbard model with d and p orbitals is investigated by using a quantum variational Monte Carlo method (VMC) with focus on the underdoped region of high-T-c superconductors. The antiferromagnetic (AF) state is considerably stable compared to the d-wave pairing state in the underdoped region, and is further stabilized by introducing spin modulations and stripes. A possibility of pure d-wave pairing state in the underdoped region is small since this state is overwhelmed by the AF ordering for small doping. The VMC evaluations show that the superconducting state is realized as a coexistence state of d-wave and AF states in the low-doping region. In particular, the non-uniform pairing state along with stripes is possible with the oscillating superconducting order parameter in space. (C) 2002 Elsevier Science Ltd. All rights reserved.