Singlet state, antiferromagnetism and disorder in high Tc cuprates

It is now established, both experimentally and theoretically, that the disorder in the spin-Peierls systems, CuGeO3, can introduce a coexistence of lattice dimerization and antiferromagnetism in the ground state and the excitation spectra in such a coexistent state has a dual structure: a gap mode together with the low lying gapless excitations. Based on this understanding, the nature of the pseudo-gap and the effects of disorder thereupon (replacement of Cu by Zn) in high T-c cuprates will be discussed briefly. (C) 2000 Elsevier Science Ltd. All rights reserved.