Microscopic model for the structural transition and spin gap formation in alpha(')-NaV2O5

摘要: We present a microscopic model for ${\ensuremath{\alpha}}^{\ensuremath{'}}\ensuremath{-}{\mathrm{NaV}}_{2}{\mathrm{O}}_{5}.$ Using an extended Hubbard the vanadium layers we derive effective low-energy consisting of pseudospin Ising chains and Heisenberg coupled to each other. find ``spin-Peierls-Ising'' phase transition which causes charge ordering on every second ladder superexchange alternation other ladders. This can be identified with first two close-by transitions observed in experiment. Due coupling between lattice is enhanced. demonstrated within Slater-Koster approximation. It leads instability charge-ordered ladders due alternating shift O sites rungs that ladder. explain our spin gap, anomalous BCS ratio, critical temperature magnetic field. To test calculated superstructure determine magnon dispersion agreement