title: Charge-order-driven spin-peierls transition in alpha(')-NaxV2O5
abstract: We conclude from 23Na and 51V NMR measurements in alpha(')-NaxV2O5 (x = 0.996) (i) a charge-ordering transition starting at T</=37 K and preceding the lattice distortion and (ii) the formation of a spin gap Delta = 106 K at T(c) = 34.7 K. Above T(c), only a single Na site is observed in agreement with the Pmmn space group of this first 1/4-filled ladder system. Below T(c) = 34.7 K, this line evolves into eight distinct 23Na quadrupolar split lines, which evidences a lattice distortion with, at least, a doubling of the unit cell in the (a,b) plane. A model for this unique transition, implying both charge density wave and spin-Peierls order, is discussed.
authors.affiliation: Physikalisches Institut, Universitat Stuttgart, 70550 Stuttgart, Germany.
authors.initials: Y
authors.lastname: Fagot-Revurat
authors.initials: M
authors.lastname: Mehring
authors.initials: RK
authors.lastname: Kremer