Magnetic bound states in the quarter-filled ladder system $\hat{I}{\pm }^{\prime }-Na{V}_2{O}_5$}

Abstract

Raman scattering in the quarter-filled spin ladder system alpha'-NaV_2O_5 shows in the dimerized singlet ground state ($T\le T_{SP}=35K$) an unexpected sequence of three magnetic bound states. Our results suggest that the recently proposed mapping onto an effective spin chain for $T>T_{SP}$ has to be given up in favor of the full topology and exchange paths of a ladder in the dimerized phase for $T<T_{SP}$. As the new ground state we propose a dynamic superposition of energetically nearly degenerate dimer configurations on the ladder.

5 pages, 4 figures, to be published in PRB, brief reports, Dec. 1998