Spin Dynamics of the One-Dimensional J-J' Model and Spin-Peierls Transition in CuGeO_3

概要

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Spin dynatnics as well as static properties of the one-dirnensional J-J' model (S = 172, J >Oand O< a = J'/ J< 0.5) are sttrdied by the ex;tct diagonalization and the recursion method offinite systems up to 26 sites. Especially, the dynamical structtrre factor S(q, w) is investigatedcarefully for various values of a. As a increases beyond the gapless-gapful critical value a.0.2411, there appear features definitely different from the Heisenberg znodel but the same withthe Ma.jumdar-Ghosh rnodel. Sotne of these features depend only on the value of Q and not on (5:a paranneter introduced for the coupling altern?ttion. By cornparing these results with a recentinelastic neutron scattering spectrum of an irtorganic spin-Peierls conapotrnd CuGe03 [lVI. Araiet al.o Phys, Rev. Lett. 77 (1996) 3649], it is ['otmnd that the frustration by J' in CuGeO3 isunexpectedly strong (o : 0.4-0.45), and at least cx must be larger than a. to some extent. Thevalue of J is evaluated at x 180 K consistent with other estimations. The cotupling alternation isextremely small. This large frtrstration is a primary origin of the variotrs anornalotms propertiesCuGeO3 possesses. For comparison we refer also to a'-NaV3O5.
社団法人日本物理学会の論文
1997-11-15