1999/09/27 by G. Bouzerar, Örs Legeza, O. Legeza +2 · 1 citation
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.60.15278
7 pages latex, figure included, accepted in PRB (issue dec.99)
arxiv created 1999/09/27 · openalex publication_date 1999/12/01 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We show that to describe properly the low-energy excitations of CuGeO3 one must include the effects of a transverse antiferromagnetic coupling, which is estimated to be J_\ensuremath⊥=0.15J. Owing to this coupling the frustration in the chains is significantly lower than recent one-dimensional (1D) estimates based on purely one-dimensional arguments, we find J2=0.2J. Furthermore, we have found a strong modulation of the nearest-neighbor coupling due to the static distortion \ensuremathδ=0.065, which is five times higher than that previously deduced from a 1D chain approach. Our set of parameters gives (i) a value of the distortion which agrees well with some recent estimate for a lower bound we are able to perfectly reproduce, (ii) the dispersions, and (iii) the experimental susceptibility at both high and low temperatures. By performing density matrix renormalization-group (DMRG) calculations for two coupled chains we have analyzed the effect of the transverse coupling on the ratio of singlet to triplet gaps. The ratio is very sensitive to the parameters and the universality reported in the strict one-dimensional case is lost. As an additional point, we provide a simple picture to explain the interesting feature observed in recent inelastic neutron-scattering experiments: the existence of a second branch of excitations.