Theory of slightly doped Mott insulator

Wave functions (wfs) for the slightly doped Mott insulator are studied numerically to reveal the nature of the doped holes/electrons. It is found that a common variational wf reproduces the dispersion of both a single hole and an electron observed experimentally. This is due to the fact that the quantum fluctuation dominates in the quantum antiferromagnet, and the wf is robust against the hole/electron doping. Besides this quasi-particle state, the novel spin liquid state is found to be stabilized at k = (pi, 0) by t' and t" values appropriate for hole doped case. For more holes/electrons, we propose a new wf which has lower energy compared with the projected SDW + d-RVB state. This state has much less superconducting correlation with the small pocket of the Fermi surface. (C) 2003 Elsevier Science B.V. All rights reserved.