DENSITY-FUNCTIONAL STUDY OF ANTIFERROMAGNETIC SPIN CORRELATIONS IN LAYERED ELECTRONS - CONDUCTIVE SPIN-DENSITY-WAVE STATES

It is shown in the density-functional theory that a two-dimensional (2D) layer of electrons may have an inhomogeneous spin-density-wave (SDW) ground state, induced by net attraction between nearest-neighbor electrons with antiparallel spins due to the exchange-correlation potentials stemming from the second-order exchange processes. Phase diagrams of the spin-inhomogeneous ground states for such 2D electrons are obtained in terms of the antiferromagnetic order parameters. The results predict that spin-inhomogeneous conductive states exist between the onset of a SDW instability and the eventual antiferromagnetic Mott-insulator states; analyses of the Fermi-surface structures and the densities of states substantiate that these SDW electrons are itinerant. Stability of those SDW states against thermal fluctuations, spatial modulation due to a lattice field, and hole injection is also examined. It is thus suggested that the conductive SDW states may play a key role in elucidating the microscopic mechanisms of high-temperature superconductivity.